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Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 9 Heat Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 9 Heat Question Answer Maharashtra Board

Class 7 Science Chapter 9 Heat Question Answer Maharashtra Board

Fill in the blanks:

Question a.
Maximum heat is absorbed by a ………….. coloured object.
Answer:
black

Question b.
……………. of heat does not require a medium.
Answer:
Radiation

Question c.
Conduction of heat takes place through a ……………. substance.
Answer:
solid

Question d.
The shining surface in a thermos flask decreases the outgoing heat by ……………… .
Answer:
reflection

Question e.
Cooking utensils are made from metals due to their property of ……………… .
Answer:
conduction

Question f.
The earth receives heat from the sun by ………………. .
Answer:
radiation

2. What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.

Question a.
What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.
Answer:
Following will absorb heat fast: steel spoon, iron griddle, water, wax. Remaining objects also obsorb heat but very slowly.

3. Write Answers to the following questions. 

Question a.
How does a fever get lowered by putting a cold compress on the forehead of a patient?
Answer:
The water in the cold compress will evaporate by the heat of fever thus taking some local heat of the body and temperature of the body is lowered, therefore the fever gets lowered by putting a cold compress on the forehead of a patient.

Question b.
Why are the houses in Rajasthan painted white?
Answer:
Rajasthan being a desert, temperature is very high. So there is excess heat. White colour doesn’t absorb the heat but reflects back, so houses will not become hot due to excess heat and inside of the house will be cool. So the houses in Rajasthan are painted white.

Question c.
What are the modes of heat transfer?
Answer:
There are three modes of heat transfer:

1. conduction
2. convection
3. radiation.

Question d.
Explain which mode of heat transfer causes sea breezes and land breezes?
Answer:

1. Unequal heating of air above the sea and land sets up convection currents which cause sea breezes during the day time.
2. The land near the sea is heated by sunlight to a higher temperature than the sea.
3. As the air above the land is heated, it becomes lighter and moves upwards, its place is then taken by cooler air moving from the sea towards the land.
4. Sea breezes are thus set up. At night, the land cools faster than water in the sea. Therefore air above sea water is hotter than air above the land.
5. So cooler air from the land moves towards the sea forming land breeze.

Question e.
Why is the outer coat of the penguins of Antarctica black?
Answer:
The outer coat of the penguins of Antarctica is black because black colour absorbs heat so penguins get lots of heat due to this black colour and they can live easily in very, very cold Antarctica region.

Question f.
Why are heaters fitted near the floor and air conditioners near the ceiling of a room?
Answer:
1. Due to air conditioners, air becomes cool so its density increases and it becomes heavy. So it goes down and warm air with less density comes up and take the place of cold air. This cycle goes on and on and the whole room becomes cool.
2. If it is fitted near the floor then cool air of high density can’t go up and upper air with low density cannot come down and cooling of the room does not take place properly so air conditioners are fitted near the ceiling of a room.
3. Heaters are fitted near the floor. Due to heating, air becomes hot which is lighter than cold air. So it goes up and upper air with high density comes down.
4. This cycle goes on and on and the full room becomes warm. So heaters are fitted near the floor.

4. Give scientific reasons.

Question a.
An ordinary glass bottle cracks when boiling water is poured into it, but a borosil glass bottle does not.
Answer:

1. An ordinary glass bottle cracks when we pour boiling water into it because there is a lot of temperature difference between the inner and outer parts of the glass.
2. The inner part gets hot and expands while the outer part remains cold since glass is a bad conductor of heat.
3. This unequal expansion causes the crack of glass bottle.
4. But the borosil glass bottle has a very high melting point so the temperature difference is very less, hence it doesn’t crack.

Question b.
The telephone wires which sag in summer become straight in winter.
Answer:

1. Telephone wires are made up of copper metal. Metals expand on heating.
2. In summer the copper wire expands, thus the length of the wire increases between the two poles and instead of remaining straight it sags.
3. In winter due to cold, it contracts and comes back to the original position, so it becomes straight in winter.

Question c.
Dewdrops form on the grass in winter.
Answer:

1. During the winter, the temperature of air is low, its capacity to hold the vapour is less.
2. At such times the excess water vapour is transformed into water droplets due to cold. And so the dew drops form on the grass in winter.

Question d.
In winter, why does an iron pillar feel colder than a wooden pole.
Answer:

1. Iron is a metal and metals are very good conductors of heat so it transfers heat at a much faster rate than wood.
2. That means, when we touch them, metals conducts away energy in the form of heat emitted by our hand and temperature of our hand lowers down and we get a cold’ sensation.
3. This is what makes the metal appear colder than the wood.
4. The wood is taking away heat at a much slower rate.

Project:

Question 1.
Make a note of the various examples of heat transfer seen in day-to-day life.

Class 7 Science Chapter 9 Heat Important Questions and Answers

Fill in the blanks:

Question 1.
………………… is an indicator of the heat in a substance.
Answer:
Temperature

Question 2.
………………. flows from higher temperature to lower temperature.
Answer:
Heat

Question 3.
Transfer of heat from one place to another takes place by ……………. or ……………. .
Answer:
conduction, convection, radiation

Question 4.
During conduction, particles of the substance …………….. in their place.
Answer:
vibrate

Question 5.
In a convection current, warm air travels …………….. .
Answer:
upwards

Question 6.
A …………….. is necessary for the conduction of heat.
Answer:
medium

Question 7.
The ………………. of conduction of heat through a medium depends on the medium.
Answer:
speed

Question 8.
Convection takes place only in …………… medium.
Answer:
fluid

Question 9.
Transfer of heat in the absence of a medium is called ……………… .
Answer:
radiation

Question 10.
Substances through which heat travels easily and quickly are called …………… .
Answer:
good conductors

Question 11.
Substances through which heat travels very slowly are called ………… of heat.
Answer:
bad conductors

Question 12.
Copper is a better ………… of heat than …………. .
Answer:
conductor, iron

Question 13.
………………. made first thermos flask in 1892.
Answer:
Sir James Dewar

Question 14.
Neither conduction nor convection of the heat occurs in thermos flask due to the ……………… .
Answer:
vacuum.

Match the following:

Question 1.

Column ‘A’	Column ‘B’
1. Good conductor	a. flow of particles
2. Bad conductor	b. particles vibrate
3. Conduction	c. glass
4. Convection	d. copper

Answer:

Column ‘A’	Column ‘B’
1. Good conductor	d. copper
2. Bad conductor	c. glass
3. Conduction	b. particles vibrate
4. Convection	a. flow of particles

Question 2.

Column ‘A’	Column ‘B’
1. Radiation	a. convection current
2. Black body	b. conduction
3. Vibration	c. absorbs more heat
4. A rotating paper lantern	d. no medium

Answer:

Column ‘A’	Column ‘B’
1. Radiation	d. no medium
2. Black body	c. absorbs more heat
3. Vibration	b. conduction
4. A rotating paper lantern	a. convection current

Say whether true or false, correct and rewrite the false statements:

Question 1.
Glass is a bad conductor of heat.
Answer:
True

Question 2.
In a thermos flask, hot things remain hot and cold things become warm.
Answer:
False. In a thermos flask, hot things remain hot and cold things remain cold.

Question 3.
Radiation of heat depends upon the colours of the outer surface of the body.
Answer:
True

Question 4.
During radiation, the particles of the medium vibrate.
Answer:
True

Question 5.
Copper is better conductor of heat than iron.
Answer:
True

Question 6.
During conduction, particles of the conductor leave their original place.
Answer:
False. During conduction, particles of the conductor do not leave their original place, but only vibrate in their own place.

Question 7.
Hot water is heavier than cold water.
Answer:
False – Hot water is lighter than cold water.

Question 8.
A convection current always travels down wards.
Answer:
False – A convection current always travels upwards.

Question 9.
Every warm substance continuously emits heat in all directions around itself.
Answer:
True

Question 10.
Air is a bad conductor of heat.
Answer:
True

Define the following:

1. Conduction
2. convection
3. radiation
4. Transfer of heat.

Answer:

1. Conduction: The transfer of heat from one end of a solid substance to the other, without the particles leaving their original place is called conduction.
2. Convection: Transfer of heat in fluids due to formation of currents is called convection.
3. Radiation: Transfer of heat in all directions in the absence of a medium is called radiation.
4. Transfer of heat: The flow of heat from one place to another is called transfer of heat.

Give scientific reasons:

Question 1.
Cricketers wear white clothes when playing in the sun.
Answer:
White clothes do not absorb heat but reflect back therefore cricketers wear white clothes while playing in the sun.

Question 2.
Sawdust is a bad conductor of heat.
Answer:
Sawdust is a bad conductor of heat because heat travels very slowly through it.

Question 3.
We can feel the heat of table lamp under it.
Answer:
We can feel the heat of table lamp under it because every warm substance continuously emits heat in all directions around itself by radiation.

Question 4.
Medium is necessary for conduction.
Answer:
Conduction is the transfer of heat from one end of a substance to another. Transfer of heat has to be done by particles of a substance and particles of a substance are particles of a medium. Hence, a medium is necessary for conduction.

Question 5.
Explain the structure and functioning of thermometer containers-
Answer:

1. Thermoware containers keep food hot. These containers consist two boxes fitted one inside the other.
2. The outer box is made up of plastic while the inner one is made up of a shiny metal, there is air between the two boxes.
3. Air is a bad conductor of heat. Thus, heat is not lost by either conduction or convection. Also, the shiny inner surface prevents heat loss due to radiation.
4. The container has a plastic lid. This also prevents any transfer of heat.

Question 6.
what is mailed infrared camera? Write its uses.
Answer:

1. Radiation of heat takes place from many objects in nature such as trees, mountains, stones and roads.
2. A camera has been developed which uses these radiations to make our surroundings visible even at night. This is called infrared camera.
3. It is used to keep watch on the movements of the enemy during the night.
4. It is also used to track the movements of animals in the wild.

Question 7.
Why is mercury used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.

1. There is a big difference between the freezing point and boiling point of mercury. Its freezing point is – 39° C and its boiling point is 357° C.
2. It is shiny and can be easily seen.
3. It does not stick to glass.
4. It expands regularly and uniformly in all conditions.

Question 8.
Write the difference between Conduction, Convection and Radiation.
Answer:

Conduction	Convection	Radiation
1. It is a mode of transfer of heat from hot part of an object to the cold part.	It is a mode of transfer of heat by means of convection currents.	It is a mode of transfer of heat in all directions without any medium.
2. It occurs in solids.	It occurs in liquids and gases.	It occurs in all objects of high temperature and vacuum.
3. It is a slow process.	It is a slow process	It is a fast process.

Question 9.
Draw and explain about the Thermos flask or Dewar flask.
Answer:

Principle:
1. As there is no medium in the vacuum between the two bottles, no transfer of heat can take place by conduction or convection.
2. Radiant heat is reflected back inside from the shiny surfaces.
3. Glass and plastic are bad conductors of heat hence they do not transfer heat either into or out of the bottle. Thus transfer of heat does not take place by any of the three modes, namely conduction, convection or radiation Hence, hot things in the flask remain hot and cold things cold.

Structure:

1. A thermos flask consists of two thin glass bottles fitted one inside the other.
2. The inner surfaces of the bottles have a silver coating to shine like a mirror.
3. A vacuum is created in the space between the two bottles by removing all the air from it.
4. A plastic or cork lid is provided to fit on the mouth of the bottle.

Draw neat labelled diagrams of:

Question 1.
The relation between density and convection
Answer:

Question 2.
Conduction of heat
Answer:

Question 3.
Convection of heat
Answer:

Question 4.
Expansion and contraction of a liquid
Answer:

Question 5.
Thermos flask
Answer:

Can you tell?

Answer the following questions:

Question 1.
Why does the halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai?
Answer:
The halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai because (i) His slotted spoon is made up of metal and metal is a good conductor of heat so due to constant heating spoon gets very hot which makes hand to get burnt, (ii) But cloth is a bad conductor of heat so it does not allow heat to reach till hand and halwai does not feel hot when he stirs the boiling milk.

Question 2.
Why do we hold a steel glass in a handkerchief while drinking hot milk from it?
Answer:

1. Steel is metal and it is a good conductor of heat. So due to hot milk it becomes hot and it is difficult to hold. Person’s hand get burnt due to it.
2. So it is better to hold in a handkerchief because handkerchief is made up of cloth which is a bad conductor of heat. So your hand does not feel hot.

Use your brain power!

Question 1.
Why do we wear woollen clothes in winter?
Answer:
We wear woollen clothes in winter because

1. Air is a poor conductor of heat and woollen clothes do not allow the transfer of body heat.
2. Therefore we do not feel cold in woollen clothes and get protected from cold in winter.

Question 2.
Why do we use white clothes in summer and dark or black clothes in winter?
Answer:

1. White clothes do not absorb heat, so in summer, weather is very hot and white clothes protect us from heat whereas in winter it is very cold so we need more heat.
2. Dark or black clothes absorb more heat so we get protection from cold.

Question 3.
Why is there a gap at the joints of rails and of cement concrete bridges?
Answer:

1. The joints of rails and cement concrete bridges are made of iron. Metal is a good conductor of heat so in summer due to heat it expands and its length will be increased.
2. To allow for this expansion, gaps are kept.
3. If these gaps are not kept, then after expansion the rails and cement concrete would have buckled upwards due to lack of space.
4. Due to that bridges would crack and railway tracks get crooked.

Question 4.
Why is mercury or alcohol used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.
Alcohol is used in a thermometer for the following properties.

1. It can measure a low temperature because its freezing point is low. (-115°C) but it can not measure higher temperature as its boiling point is low.
2. It can measure the temperature precisely because it has large expansion coefficient.
3. It’s expansion is regular.
4. Less hazardous.

Question 5.
Why hot substance does not remain as hot after two or three hours?
Answer:
A little heat is lost from around the lid and by a small amount of conduction through the vessel. So hot substance does not remain as hot after two or three hours.

Diagram based questions.

Observe the diagram and answer the given questions below it.

1.

Question a.
What is the diagram about?
Answer:
The diagram is showing us the relation between density and convection.

Question b.
Why is the ice wrapped in wire gauze?
Answer:
Ice floats on water, to make it sink, it is wrapped in wire gauze.

Question c.
What does this experiment prove?
Answer:
When a liquid is heated, its density decreases and it rises upwards. This leads to the convection currents which makes the heated liquid rise upwards and cooler liquid takes it place.

2.

Question a.
What is the diagram about?
Answer:
Expansion and contraction of a solid substance.

Question b.
Does the same thing happen in liquids and gases?
Answer:
Yes. Generally substances solids, liquids and gases expand on heating and contract on cooling.

Question c.
Give one example of this property in everyday life.
Answer:
Gaps are present in between two railway line track joints so that they do not bend due to expansion.

3.

Question a.
Label parts 1 – 4
Answer:

1. Vacuum
2. metal/plastic jar
3. Spring
4. silvered surface of the glass.

Question b.
What is the principle of this object?
Answer:
As there is no medium in the vacuum between the two bottles, no transfer of heat takes place due to conduction and convection and radiated heat is reflected back by the shiny surface.

Question c.
State the uses of the given object.
Answer:
The temperature of substances inside it are maintained for some time. Hot things remain hot and cold things cold for 2 – 3 hours.

Question d.
What is an infrared camera?
Answer:
It is a camera which uses radiations to make our surroundings visible at night. Using this camera, it is possible to keep a watch on the movements of the enemy during the night.

Question e.
What is thermoware?
Answer:
Thermoware are object which do not allow heat to escape from them. So things stay warm in them. eg. hot pot, thermos flask.

7th Std Science Questions And Answers:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 4 Nutrition in Living Organisms Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 4 Nutrition in Living Organisms Question Answer Maharashtra Board

Class 7 Science Chapter 4 Nutrition in Living Organisms Question Answer Maharashtra Board

1. Classify according to food-type.
Tiger, cow, vulture, bacteria, deer, goat, human, fungus, lion, sparrow, buffalo, frog, cockroach, tick.
Answer:

• Carnivores: tiger, Lion
• Herbivores: cow, deer, goat, buffalo
• Scavengers: vulture
• Decomposers: fungus, bacteria
• Granivores: sparrow
• Insectivores: frog Parasitic: tick
• Omnivores: human, cockroach

2. Nutrition In Living Organisms Class 7 Exercise Match the pairs.

Class 7 Science Chapter 4 Nutrition In Living Organisms Question Answer Question 1.

Column ‘A’	Column ‘B’
1. Parasitic plant	a. Mushroom
2. Parasitic plant	b. Lichen
3. Saprophytic plant	c. Drosera
4. Symbiotic plant	d. Cuscuta

Answer:

Column ‘A’	Column ‘B’
1. Parasitic plant	d. Cuscuta
2. Parasitic plant	c. Drosera
3. Saprophytic plant	a. Mushroom
4. Symbiotic plant	b. Lichen

3. Answer the following questions in your words. 

Question a.
Why do living organisms need nutrition?
Answer:
Living organisms need nutrition due to the following: (a) To supply the energy required for doing work, (b) For growth and development of the body, (c) To replace the damaged cells and repair tissues, (d) To fight diseases.

Question b.
Explain the process of production of food in plants.
Answer:
1. Green plants can produce their own food. With the help of sunlight and chlorophyll, plants make their own food in their leaves, using water and nutrients from the soil and carbon dioxide from the air.

2. This process is called as photosynthesis. In this process plants give out oxygen and take in carbon dioxide.

Question c.
What is meant by parasitic plants? Name their different types with examples of each.
Answer:
The plants that grow on the body of other plants to obtain food are called as parasitic plants.

There are two types of parasitic plants:

• Holoparasites: e.g. Rafflesiaceae
• Hemiparasites: e.g. Loranthaceae

Question d.
Explain the various steps of nutrition in animals.
Answer:
Steps of nutrition in animals are as follows:

1. Ingestion: Food is taken into the body.
2. Digestion: Conversion of food into simple soluble forms.
3. Absorption: Transfer of soluble food to the blood.
4. Assimilation: Utilization of absorbed food by cells and tissues for energy production, growth and repair.
5. Egestion: Removal of waste products and undigested food from body.

Question e.
Name some unicellular organisms in which all life processes take place within their unicellular body.
Answer:
Unicellular organisms like amoeba, euglena, paramoecium in which all life processes take place within their unicellular body.

4. Give reasons.

Question a.

Insectivorous plants are attractively coloured.
Answer:

1. Insectivorous plants generally grow in soil or water deficient in nitrogen compounds.
2. The plant body of the Drosera burmanii has a flower like appearance. It grows close to the ground. Even its leaves are attractively pink or red in colour with hairs at the margin.
3. Droplets of a sticky substances found on tips of the hairs attract insects.
4. These plants consume insects to fulfill their need for nitrogen. To attract the insects these plants are attractively coloured.

Question b.
Butterflies have a long tube-like proboscis.
Answer:
Holozoic mode of nutrition means the feeding of solid and liquid food by animals. Butterflies live on nectar from flowers. Therefore to suck the nectar from flowers, they have a long tube-like structure called proboscis.

5. Prepare and complete the flowchart according to type of nutrition.

Question a.
Prepare and complete the flowchart according to type of nutrition.

Answer:

6. Think and answer.

Question a.
We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms?
Answer:

1. We prepare a variety of foodstuffs and dishes at home but we are not autotrophic organisms.
2. In autotrophic organisms they have chlorophyll in their body and food is prepared here with help of sunlight, water and CO₂ for the organisms.
3. But the food which we prepare at home is not generated in our body.

Question b.
Which organisms are greater in number – autotrophs or heterotrophs? Why?
Answer:

1. Autotrophs have chlorophyll in the cell and here the organic food is prepared using sunlight, water and CO₂.
2. They do not depend on any other organism for survival.
3. But the heterotrophs depend on autotrophs and other organisms for survival. Hence autotrophs are more in number than heterotrophs.

Question c.
The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why is this so?
Answer:

1. In desert region due to scarcity of water and excess heat, very few cactus are found as autotrophs compared to sea. As autotrophs are less, number of heterotrophs dependent on autotrophs are smaller.
2. Whereas in sea due to greater numbers of autotrophs, greater number of heterotrophs are found.

Question d.
What damage or harm do ectoparasitic and endoparasitic animals cause?
Answer:

1. Ectoparasitic animals suck the blood of the animal on which it remains and endoparasitic animals get readymade food from the body of animal in which it remain.
2. This way both the parasites make the animal weak by sucking their blood or by eating prepared food from them.

Question e.
Why is plant food not produced in any other parts of the plant except the green ones?
Answer:
Plant food is not produced in any other parts of the plant except the green ones because only green part contains chlorophyll and chlorophyll is very necessary for the production of food.

Class 7 Science Chapter 4 Nutrition In Living Organisms Project:

Question 1.
Many heterotrophic organisms live on one and the same plant. Observe one such plant in your neighborhood and find out about the heterotrophs that depend upon it for their food. Observe and make flotes about other organisms that use these heterotrophs as their food.

Question 2.
Prepare a Power point presentation on the topic ‘Nutrition in Living Organisms’.

Class 7 Science Chapter 4 Nutrition in Living Organisms Important Questions and Answers

Nutrition In Living Organisms Class 7 Exercise Fill in the blanks.

Nutrition In Living Organisms Class 7 Exercise Question 1.
Leaves have microscopic openings called ……………. .
Answer:
Stomata

Class 7 Science Chapter 4 Nutrition In Living Organisms Question 2.
In the process of photosynthesis plants take in ……………. and ……………. gas is given out.
Answer:
Carbondioxide, oxygen

Question 3.
The ……………. transports minerals and water from roots to all aerial parts of the plant.
Answer:
xylem

Question 4.
The ……………. transports the food from the leaves to other parts of the plant.
Answer:
phloem

Question 5.
Plants produce ……………. by the process of photosynthesis.
Answer:
Carbohydrates

Question 6.
……………. are made from carbon, hydrogen, oxygen.
Answer:
Carbohydrates

Question 7.
……………. are made from carbon, hydrogen and oxygen and nitrogen.
Answer:
proteins

Question 8.
……………. plants contain rhizobium micro-organisms.
Answer:
leguminous

Question 9.
Micro-organisms like ……………. are present in soil.
Answer:
azotobacter

Question 10.
Lichen is of a symbiosis between ……………. and ……………. .
Answer:
algae, fungi

Question 11.
The scientist ……………. identified Drosera plant in Sri Lanka in 1737.
Answer:
Johannes Burman

Question 12.
Fungi like mushroom and yeast are ……………. .
Answer:
saprophytes

Question 13.
Removal of waste products and undigested food from the body is called …………….
Answer:
Egestion

Question 14.
Amoeba moves with the help of ……………. .
Answer:
pseudopodia

Question 15.
Butterflies suck food with a tube like ……………. .
Answer:
proboscis

Question 16.
The ……………. or ……………. is an ant eating animal found in India.
Answer:
bobcat, udmanjar

Question 17.
Seed eating animals are called ……………. .
Answer:
granivores

Question 18.
Fruit eating animals are called ……………. .
Answer:
frugivores

Question 19.
Animals that obtain their food from both plants and animals are called ……………. .
Answer:
Omnivores

Question 20.
Roundworms are known as ……………. .
Answer:
endoparasites

Class 7 Science Chapter 4 Nutrition In Living Organisms Match the column:

Question 1.

Column ‘A’	Column ‘B’
1. Endoparasite	a. Vulture
2. Ectoparasite	b. Human
3. Seed eating animals	c. Tapeworm
4. Fruit eating animals	d. Bed bug
5. Scavenger	e. granivores
6. Omnivore	f. frugivores

Answer:

Column ‘A’	Column ‘B’
1. Endoparasite	c. Tapeworm
2. Ectoparasite	d. Bed bug
3. Seed eating animals	e. granivores
4. Fruit eating animals	f. frugivores
5. Scavenger	a. Vulture
6. Omnivore	b. Human

Say whether true or false, correct and rewrite the false statements.

Question 1.
Bed bug is an example of endoparasitic nutrition.
Answer:
False, Bed bug is an example of ectoparasitic nutrition

Question 2.
Spider shows saprozoic nutrition.
Answer:
True

Question 3.
The anteater is found in India.
Answer:
False. The anteater is found in Central and South America

Question 4.
Yellowing of leaves occur due to deficiency of iron.
Answer:
True

Question 5.
Mushroom is used in making bread.
Answer:
False. Yeast is used in making bread

Question 6.
Cuscuta is completely a parasitic plant.
Answer:
True

Question 7.
The nitrogen dioxide dissolves in rainwater and is converted into nitric acid.
Answer:
True

Question 8.
Micro-organism Rhizobium is found in soil.
Answer:
False. Micro-organism Azotobacter is found in soil.

Question 9.
Fixation of nitrogen occurs by biological and atmospheric methods.
Answer:
True

Question 10.
The chloroplasts present in the leaves contain chlorophyll.
Answer:
True

Question 11.
Decomposers obtain their food from living organisms.
Answer:
False, They obtain their food by decomposing the dead bodies of organisms or other materials

Question 12.
Carbondixode is given out during the process of photosynthesis.
Answer:
False, Oxygen is given out during the process of photosynthesis

Question 13.
Phloem transports the food from leaves to other parts of the plant.
Answer:
True

Question 14.
Carbohydrates are made up of carbon, hydrogen oxygen and nitrogen.
Answer:
False, Protein are made up of carbon, hydrogen, Oxygen and nitrogen.

Give scientific reasons.

Question 1.
Micro-organisms like Rhizobium are useful.
Answer:

1. Rhizobium micro-organisms are useful because plants cannot take gaseous nitrogen from air.
2. These micro-organisms absorb atmospheric nitrogen and convert it into its nitrate, a compound which is useful for plant.

Question 2.
Lichen is an example of a symbiotic nutrition.
Answer:
Lichen is a symbiosis between algae and fungi in which fungi provides water, minerals, as well as shelter to algae and in return the algae Master Key General Science (Std. 7), provide food to the fungi. So Lichen, is an example of symbiotic nutrition.

Question 3.
Drosera burmanii is an insectivorous plant.
Answer:
Drosera burmanii grows in a soil which has nitrogen deficiency. It feeds upon insects to obtain nitrogen, so it is an insectivorous plant.

Question 4.
Human is an omnivore.
Answer:
Humans obtain their food from both, plants and animals so human is an omnivore.

Question 5.
Tapeworm is an endoparasite.
Answer:
Tapeworm lives inside the body of other animals and obtain its food. So tapeworm is an endoparasite.

Question 6.
Decomposers are important for the ecosystem
Answer:
Decomposers feed on dead and decaying matter and therefore indirectly clean the ecosystem. If decomposers were not there then nutrients would not be able to return back and get recycled. Therefore decomposers are very important for the ecosystem.

Question 7.
Cuscuta is a total parasite while Loranthus is a partial parasite.
Answer:
Cuscuta is a nongreen yellow thread-like plant completely dependent on the host plant, loranthus is a partial parasitic because it can prepare its own food and it only takes water and minerals from the host plant.

Answer the following in your own words:

Question 1.

Classify the types of nutrients.
Answer:
There are two types of nutrients.

1. Nutrients like carbohydrates, proteins and fats are required in large quantity. These are macro-nutrients.
2. Minerals and vitamins are required in very small quantity. They are called micro-nutrients.

Question 2.
Explain the types of nutrition.
Answer:
There are two types of nutrition.

1. Some organisms can produce their own food and thus nourish themselves. This is called autotrophic nutrition.
2. Some organisms depend on other organisms, plants and animals for their food. This is called heterotrophic nutrition.

Question 3.
Write differences between xylem and phloem.
Answer:

xylem	Phloem
1.  The xylem transports minerals and water from the root to all aerial parts of the plant.	1. The phloem transports the food (glucose) from the leaves to other parts of the plant where it is either consumed or stored.

Question 4.
What is chemosynthesis? Which plants produce their food by chemosynthesis?
Answer:

1. Chemosynthesis is the biological conversion of one or more carbon-containing molecules and nutrients into organic matter.
2. It uses the oxidation of inorganic compounds or methane as a source of energy rather than sunlight.
3. Sulphur bacteria and nitrosomonas produce their food by chemosynthesis.

Question 5.
Name the micro-organisms which help in biological fixation of nitrogen. How?
Answer:
Two different types of micro-organisms can bring about biological nitrogen fixation.

1. Root-nodules of leguminous plants contain the micro-organism rhizobium. These micro-organisms absorb atmospheric nitrogen and convert if into its nitrate, a compound.
2. Micro-organisms like azotobacter are’present in soil. They also convert atmospheric nitrogen into nitrates.

Question 6.
What is symbiotic nutrition? Give one example of it.
Answer:

1. Two or more than two different types of plant live together to fulfill their needs of nutrition, protection, support etc. with each other’s help. This type of nutrition is called symbiotic nutrition.
2. e.g. Lichen is an example of symbiosis between algae and fungi.

Question 7.
Write about Drosera burmanii.
Answer:

1. It is art insectivorous plant.
2. The scientist Johannes Burman identified this plant in Sri Lanka in 1737. Hence, the plant is named after him.
3. It grows close to the ground.
4. Its leaves are attractively pink or red in colour with hairs at the margin.
5. Droplets of a sticky substance found at the tips of the hairs attract insects.
6. It grows in a place where deficiency of nitrogen in the soil. To get nitrogen for its growth, it eats insects.

Question 8.
What are called saprophytic plants? Give Examples.
Answer:
Plants which obtain the food from dead and decaying bodies of other organisms are called saprophytic plants e.g. Yeast and mushrooms.

Question 9.
Classify the animals according to the type of food they eat.
microbes, vulture, monkey, tiger, lion, goat, cow, buffalo, crow, hyena, human, chimpanzee
Answer:

• Herbivores: goat, cow, buffalo.
• Carnivores: tiger, lion
• Omnivores: monkey, human, chimpanzee
• Scavengers: vulture, crow, hyena
• Decomposers: microbes

Explain the terms:

1. Herbivores: Animals that depend on plants only for their food are called Herbivores.
2. Carnivores: Animals that depend on other animals for their food are called Carnivores.
3. Granivores: Animals that eat grains (seed) are called Granivores.
4. Frugivores: Animals that eat fruits are called frugivores.
5. Omnivores: Animals that obtain their food from both plants and animals are called omnivores.
6. Scavengers: Animals that obtain their food from dead bodies of animals are called Scavengers.
7. Decomposers: Microbes which obtain their food by decomposing the dead bodies of organisms or other materials are called decomposers.
8. Ectoparasitic nutrition: Some animals live on the body surface of other animals and obtain their food by sucking their blood. This is called ectoparasitic nutrition.
9. Endoparasitic nutrition: Some animals live inside the body of other animals and obtain their food. This is called endoparasitic nutrition.
10. Symbiotic nutrition: In some cases, two or more than two different types of plants live together to fulfill their needs of nutrition, protection, support etc. with each other’s help. This type of nutrition is called symbiotic nutrition.

Write the role of different nutrients like nitrogen, phosphorus, potassium,magnesium, Iron, manganese and zinc and effects of their deficiency on plants.

Question 1.
Write the role of different nutrients like nitrogen, phosphorus, potassium, magnesium, Iron, manganese and zinc and effects of their deficiency on plants.
Answer:
Role of nutrients and effects of their deficiency on plants:

Nutrients	Function	Effects of deficiency
Nitrogen	Important components of proteins, chlorophyll and cytoplasm.	Retarded/stunted growth, yellowing of leaves.
Phosphorus	Conversion of light energy into chemical energy.	Early leaf-fail, late flowering, slow growth of roots.
Potassium	Necessary for metabolic activities.	Weak stem, wilting of leaves, failure to produce carbohydrates.
Magnesium	Production of chlorophyll	Slow/retarded growth, yellowing of leaves.
Iron	Production of chlorophyll	Yellowing of leaves
Manganese	Production of main plant hormones	Retarded growth, spotted leaves
Zinc	Production of hormones and their intermediates	Retarded growth, yellowing of leaves

Can you tell?

Answer the following question: 

Question 1.
How does ingestion occur in unicellular animals like amoeba?
Answer:

1. Amoeba does not have organs like hands and mouth.
2. It is a unicellular animal. It can take in food through any part of the surface of its unicellular body.
3. It surrounds the food particle from all sides to take it into the cell.
4. After that it digests the food with the help of different enzymes.
5. Undigested food is left behind as the amoeba moves further with the help of pseudopodia.
6. In unicellular animals like amoeba, euglena, paramoecium,. etc. all the steps of nutrition occur within their unicellular body.

Question 2.
How do plants produce their own food?
Answer:
Green plants produce their own food with the help of sunlight, chlorophyll, water, nutrients from soil and carbon dioxide from the air. This process is called as photosynthesis

Use your brain power!

Answer the following questions:

Question 1.
Write the uses of yeast and mushrooms.
Answer:
Yeast is used in fermentation processes and making bread.
Mushrooms are a rich source of vitamins and iron.

Question 2.i
Which part of the loranthus plant carries out photosynthesis?
Answer:
Leaves of the loranthus plant carries out photosynthesis.

Question 2.ii
From where do they obtain minerals and water?
Answer:
They obtain water and minerals from the xylem and phloem of the other host plant.

Question 2.iii
Why is loranthus known as a partially parasitic plant?
Answer:
Loranthus is known as partially parasitic plant because it does photosynthesis with the help of leaves but only for water and minerals it depends on other plants.

Question 3.
Why does the pitcher plant feed on insects even though it produces food by photosynthesis?
Answer:
Pitcher plants grow in a place where soil has deficiency of nitrogen compounds so to fulfill the need of nitrogen they feed on insects.

Observe the diagram and answer the following questions.

Question a.
Name the process shown in the picture.
Answer:
The process shown is photosynthesis.

Question b.
Which type of plants use the above process for their nutrition?
Answer:
Autotrophic plants (green plants) use the above process for their nutrition.

Question c.
What is the pigment in the leaf that helps in the above process?
Answer:
Chlorophyll

Question d.
Give the chemical equation of the above process?
Answer:

Question e.
What is the importance of this process to living things?
Answer:
Photosynthesis helps the plants to prepare their own food and also store it in their plant bodies. Animals depend upon this stored food for their nutrition.
During photosynthesis, oxygen is given out which is important for all living organisms for respiration.

Observe the diagram and answer the following questions.

Question a.
What is shown in the picture?
Answer:
Roots of leguminous plants having root nodules.

Question b.
What is the importance of these types of plants?
Answer:
These types of plants help to provide nitrogen to the soil.

Question c.
What is the process called?
Answer:
Biological Nitrogen fixation

Question d.
Explain the process.
Answer:
Root nodules of leguminous plants contain Rhizobium micro-organisms. These micro¬organisms convert atmospheric nitrogen into nitrates. Thus the soil becomes rich in nitrogen.

7th Std Science Questions And Answers:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 13 Changes – Physical and Chemical Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 13 Changes – Physical and Chemical Question Answer Maharashtra Board

Class 7 Science Chapter 13 Changes – Physical and Chemical Question Answer Maharashtra Board

1. Distinguish between the following.

Question a.
Physical change and Chemical change
Answer:

Physical changes	Chemical changes
1. In a physical change material may change its	1. A change which after physical properties and
shape, size, texture or state.	composition also.
2. No new compound is formed.	2. New compound /substance is formed due to chemical change.
3. The change is temporary. It is reversible.	3. The change is permanent and irreversible.
4. Examples: Evaporation of water, boiling of water, melting of ice.	4. Examples: Burning of wood, paper, souring of milk, digestion of food, rusting of iron.

Question b.
Periodic changes and Non-periodic change
Answer:

Periodic changes	Non-periodic change
1. Some changes occur again and again after a definite interval of time. Such changes are called periodic changes.	1. In this, certain changes will recur after one occurrence, it cannot be said for sure, even if they occur interval is not fixed. Such changes are called non-periodic changes.
2.  Examples: movement of clock hands in clock showing time, change of season, day and night formation, heart beat, ripening of fruit, rising and setting of the sun.	2. Examples: volcanic eruption, occurrence of an earthquake, tsunami, forest fires, freezing of water to form ice, sneezing, rusting of iron.
3. They repeat themselves after a fixed interval of time.	3. They do not repeat themselves after a fixed interval of time.

Question c.
Natural change and Man-made change
Answer:

Natural change	Man-made change
1. Changes that occur naturally on its own are called natural changes.	1. Changes that are result of human activity. Such changes are called man-made.
2. Examples ripening of a fruit, spoiling of milk, change in the climate	2. Burning of fossil fuels, deforestation, pollution of air, water and soil.

2. Under which different types can the following changes be classified?

Question a.
Conversion of milk into yoghurt.
Answer:
Manmade (useful).

Question b.
Bursting of cracker.
Answer:
Manmade (fast change).

Question c.
Occurrence of an earthquake.
Answer:
Non-periodic.

Question d.
Revolution of earth around the sun.
Answer:
Periodic. (Natural change)

Question e.
Stretching of a spring.
Answer:
Physical, reversible change.

3. Give reasons.

Question a.
While purchasing canned food, its expiry date should be checked.
Answer:

1. Canned food is processed food.
2. After certain period of time it may get spoilt due to some growth of micro-organism it may get intoxicated.
3. If we consume such food we may get food poisoning, so we should check the expiry date.

Question b.
An iron article should be given a coat of paint.
Answer:

1. When an iron article is kept for long time it gets corroded due to presence of oxygen in atmosphere.
2. Iron gets oxidized to iron oxide which forms a reddish brown layer on it and iron gets rusted.
3. It is called corrosion. Due to corrosion things become weak.
4. So an iron article should be given a coat of paint so that it is protected against corrosion.
5. Paint gives protection to iron.

Question c.
A Wooden article should be polished.
Answer:

1. When a wooden article comes in contact with moisture there is possibility of fungal growth and also termites will make wooden article brittle and break.
2. So a wooden article should be polished which forms a protective layer.
3. It does not allow the wooden article to get decayed by moisture or attacked by termite.

Question d.
Copper and brass utensils should be tinned.
Answer:

1. Due to corrosion of copper or brass a greenish layer is seen to form on it.
2. So to protect copper and brass utensils from corrosion they are coated with tin.
3. This process is called thinning.

Question e.
A dry handkerchief gets wet at once on dipping in water, but it takes long for a wet handkerchief to dry.
Answer:

1. The dry fibres of handkerchief absorbs water to its maximum capacity immediately that is why handkerchief gets wet at once.
2. When wet handkerchief dries, all the water absorbed has to become water vapour by evaporation.
3. This depends on surrounding air and heat.
4. That is why wet handkerchief takes a long time to dry.

4. What will you take into account while identifying the following:

Question a.
A physical change in a substance.
Answer:
I will take into account the following facts.

1. Whether the shape, size or state of the substance is changed.
2. Whether it is a temporary change.
3. Whether it is a reversible change.

Question b.
A chemical change in a substance.
Answer:
I will take into account the following facts.

1. Whether a new substance is formed.
2. Whether it is a permanent change.
3. Whether it is a non-reversible change.

5. Read the paragraph and note down the various types of changes it mentions.

Question a.
Read the paragraph and note down the various types of changes it mentions.
It was nearing six o’clock in the evening. The sun was setting. A breeze was blowing. Leaves on the tree were shaking. Sahil was sitting in the courtyard, rolling balls of wet soil and shaping them into various toys. Then he felt hungry and went into the house. Mother made a dough from wheat flour and fried purees. While eating hot purees, his attention was drawn outside the window. It had started raining. There was lighting too. Sahil was enjoying his dinner in the dim light.
Answer:

1. Clock showing six o’clock time – It is a periodic change.
2. Sun was setting – A periodic change.
3. Breeze was blowing – A natural change.
4. Leaves shaking – A natural change.
5. Making toys from wet soil – Physical change.
6. Making dough from wheat flour – Physical change
7. Frying purees – Chemical change.
8. Raining – Natural change.
9. Lightning – Natural change.

Project:

Question a.
Visit a place where work like powder coating. spray painting is done. Make a note of the information you obtain.

Class 7 Science Chapter 13 Changes – Physical and Chemical Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
Burning of candle is a ………………. change.
Answer:
chemical

Question 2.
Cooking of vegetable is ………………. change.
Answer:
useful

Question 3.
A man painted his main gate made up of iron to prevent it from ………………. .
Answer:
rusting

Question 4.
Galvanization is a process used to prevent the rusting of ………………. .
Answer:
iron

Question 5.
Making sugar solution is a ………………. change.
Answer:
physical

Question 6.
A physical change is generally ………………. .
Answer:
temporary

Question 7.
Grinding of wheat grain changes its size, it is a ………………. .
Answer:
physical change

Question 8.
Iron benches kept in lawns and gardens get rusted. It is a change because a new ………………. is formed.
Answer:
chemical, product.

State whether the following statements are True or False. Correct and rewrite the false statement:

Question 1.
Iron and rust are the same substance.
Answer:
False, Rust is oxide of iron.

Question 2.
Iron pipes coated with zinc do not get rusted easily.
Answer:
True

Question 3.
Formation of manure from leaves is a physical change.
Answer:
False, it is a chemical change.

Question 4.
Cutting a log of wood into pieces is a chemical change.
Answer:
False, it is a physical change.

Question 5.
Digestion of food is a chemical change.
Answer:
True

Question 6.
Melting of wax is a chemical change.
Answer:
False, it is a physical change.

Question 7.
Dissolving sugar in water is physical change.
Answer:
True

Question 8.
Changes in which new substances are formed are called physical changes.
Answer:
False, they are called chemical change.

Question 9.
Breaking down of larger food particles into smaller particles is a chemical change.
Answer:
False, it is a chemical change.

Question 10.
Setting of curd is a physical change.
Answer:
False, it is a chemical change.

Question 11.
Heating of iron is a physical change.
Answer:
True

Question 12.
Cooking a vegetable is chemical change.
Answer:
True

Question 13.
Freezing water into ice is a chemical change.
Answer:
False, it is a physical change

Define the following.

Question 1.
Physical change:
Answer:
In a physical change the material may change shapes or forms but no new compounds are formed and change can generally be reversed by reversing the conditions.

Question 2.
Chemical change
Answer:
A chemical change produces a new substance having new and different properties and which cannot be reversed by reversing the conditions.

Question 3.
Periodic change
Answer:
Some changes occur again and again after . a definite interval of time, such changes are called periodic changes.

Question 4.
Non-periodic change
Answer:
Changes that do not repeat themselves after a fixed interval of time are called non-periodic changes.

Question 5.
Reversible change
Answer:
The changes that can occur in a forward and reverse direction again and again are called reversible changes.

Question 6.
Irreversible change.
Answer:
The changes which we cannot reverse back to same thing are called Irreversible changes e.g. Burning of wood, paper.

Question 7.
Condensation
Answer:
The process by which matter changes from its vapour or gaseous state into its liquid state by cooling is called condensation.

Question 8.
Corrosion of metals
Answer:
When an iron article rusts, a reddish brown layer (of iron oxide) forms on it. A greenish layer is seen to form on a copper article. This is called corrosion of metals.

Question 9.
Galvanization
Answer:
Iron articles are given a thin coat of zinc to prevent corrosion this is called galvanization.

Question 10.
Tinning
Answer:
Copper and brass articles are coated with tin. This is called tinning.

Question 11.
Natural change
Answer:
Changes that occur naturally like ripening of a fruit, spoiling of milk are called natural changes.

Question 12.
Man-made change
Answer:
Man-made changes are result of human- activity. E.g. Burning of fossil fuel.

Question 13.
Useful change
Answer:
Many changes such as baking bread, cooking food are useful to us, they are called useful changes.

Question 14.
Harmful change
Answer:
The changes that are not useful or changes that harms living things or the environment are called harmful changes.

Name or Give two example of:

Question 1.
Two physical changes.
Answer:

1. Melting of wax
2. Melting of ice

Question 2.
Two chemical changes.
Answer:

1. Burning of wax candle
2. Burning of wood or paper.

Question 3.
Two periodic changes.
Answer:

1. Occurrence of day and night
2. change of seasons

Question 4.
Two non-periodic changes.
Answer:

1. A meteor moving across the sky.
2. A bird sitting on a tree flies away.

Question 5.
Two reversible changes.
Answer:

1. Melting of wax.
2. Freezing water into ice.

Question 6.
Two irreversible changes.
Answer:

1. Ripening of a mango.
2. Burning of wood

Question 7.
Two natural changes.
Answer:

1. Lighting in the sky.
2. Earthquake.

Question 8.
Two manmade changes.
Answer:

1. Baking bread
2. Cooking food.

Question 9.
Two useful changes.
Answer:

1. Ripening of mango
2. Curdling of milk.

Question 10.
Two harmful changes.
Answer:

1. Spoiling of milk.
2. Air pollution.

Match the following:

Question 1.

Column ‘A’	Column ‘B’
1. Photosynthesis	a. Physical change.
2. Dissolving sugar in water	b. Chemical change
3. Burning of wood	c. Man-made change.
4. Melting of wax	d. Periodic changes.
5. Digestion of food	e. Non-periodic change
6. Heartbeat	f. Chemical change.
7. Occurrence of earthquake.	g. Physical change.
8. Deforestation	h. Chemical change.

Answer:

Column ‘A’	Column ‘B’
1. Photosynthesis	b. Chemical change
2. Dissolving sugar in water	a. Physical change.
3. Burning of wood	f. Chemical change.
4. Melting of wax	g. Physical change.
5. Digestion of food	h. Chemical change.
6. Heartbeat	d. Periodic changes.
7. Occurrence of earthquake.	e. Non-periodic change
8. Deforestation	c. Man-made change.

Question 2.

Column ‘A’	Column ‘B’
1. Depositing a layer of zinc on Iron	a. Tinning
2. Souring of milk	b. Rust
3. Curdling of milk	c. Galvanization
4. Iron oxide	d.  Chemical changes
5. Depositing layer of tin on copper and brass article.	e. Man-made changes.

Answer:

Column ‘A’	Column ‘B’
1. Depositing a layer of zinc on Iron	c. Galvanization
2. Souring of milk	d.  Chemical changes
3. Curdling of milk	e. Man-made changes.
4. Iron oxide	b. Rust
5. Depositing layer of tin on copper and brass article.	a. Tinning

Distinguish between the following.

Question 1.
Reversible change and Irreversible change
Answer:

Reversible change	Irreversible change
1. The changes that can occur in a forward and reverse direction again and again is called reversible.	1. The changes which we can not reverse back to some thing are called irreversible change.
2. E.g.: (a) Melting a wax candle and obtaining the original solid wax again, (b) Stretching a rubber or spring.	2. E.g.: Burning of paper or wood cannot be undone. Wood cannot be obtained from the ash.

Under which different types can be following changes be classified:

Question 1.
Formation of curd from milk.
Answer:
Manmade change (useful), chemical

Question 2.
Burning of wood or paper.
Answer:
Manmade, chemical change.

Question 3.
Glowing of bulb.
Answer:
Manmade (fast).

Question 4.
Rusting of iron.
Answer:
Chemical change (harmful)

Question 5.
Burning of Camphor.
Answer:
Chemical change

Question 6.
Souring of milk.
Answer:
chemical change (harmful)

Question 7.
Digestion of food.
Answer:
Chemical change (useful), irreversible

Question 8.
Change of season.
Answer:
Periodic change, natural change

Question 9.
Day and night formation.
Answer:
Periodic change

Question 10.
Heartbeat.
Answer:
Periodic change

Question 11.
Water pollution.
Answer:
Manmade, harmful change

Question 12.
Air pollution.
Answer:
Manmade, harmful change

Question 13.
Burning of fossil fuel
Answer:
Manmade (irreversible change)

Question 14.
Ripening of fruit.
Answer:
Natural, chemical

Question 15.
Change-in climate.
Answer:
Natural, periodic

Question 16.
Melting of ice into water
Answer:
Physical change

Question 17.
Germination of seed.
Answer:
Natural, slow, desirable.

Question 18.
Bursting of balloon.
Answer:
Irreversible change (fast).

Give reasons:

Question 1.
The burning of wax is a chemical change
Answer:

1. Because when the cotton wick embedded in the candle is burnt, ash and smoke is formed.
2. It is not possible to make wick again from the smoke and ash.

Can you tell?

Answer the following questions:

Question 1.
We see many man-made materials in our day-to-day life. For what purpose are they produced.
Answer:
We see many man-made matrical in our day to day life. For example,

1. Air conditioners for getting cool air in houses offices and cars.
2. Wooden furniture made from wood obtained by cutting trees.
3. Refrigerators to protect food from spoiling.

Question 2.
You made a link from the glass piece. How will you change the shape of the link to give it its original shape?
Answer:
Heat the glass piece again at the link. When it becomes soft break it.

Question 3.
How will you restore the original candle after melting one ?
Answer:
Collect the melted wax and give the required shape when it is soft.

Question 4.
What comes after daytime?
Answer:
Night time (periodic change)

Question 5.
What is the next stage after sunrise?
Answer:
Sunset (periodic change)

Question 6.
What comes after a high tide in the sea?
Answer:
Low tide (periodic)

Question 7.
A bird sitting on a tree flies away.
Answer:
non-periodic change.

Question 8.
A meteor streaking across the sky.
Answer:
non-periodic change.

Use your brainpower!

Answer the following questions:

Question 1.
What kind of change is the falling of a tree in a storm?
Answer:
Natural change.

Question 2.
What kind of a change is the conversion of milk into yoghurt?
Answer:
Manmade ‘ change, useful change and a chemical change

Question 3.
What is meant by irreversible change? Give some examples.
Answer:

1. An irreversible change is a permanent change that cannot be undone, cannot reverse it back to original substance.
2. In irreversible change new materials are always formed.
3. Irreversible changes are permanent changes.
4. Heating, burning, mixing, powdering are few processes which causes irreversible changes.

Examples:

• burning of paper or wood
• cooking of raw egg.

Question 4.
Which type of change is the change of seasons from summer to rains to winter?
Answer:
Natural and periodic change

Question 5.
Which hands of a clock show periodic changes from 6.00 am to 6.00 pm? How many times?
Answer:
Small (hour) hand (12 times).

Question 6.
Which of the following are physical changes and which are chemical changes?
(making a table from wood, burning wood, breaking of a glass object, ripening of a tomato, rusting of iron.
Answer:

Physical	Chemical
1. Making a table from wood	1. Burning wood
2. Breaking of a glass object	2. Rusting of iron
	3. Ripening of a tomato

Question 7.
What are periodic and non-periodic changes?
Answer:
1. We find that some changes occur again and again after a definite interval of time. Such changes are called Periodic changes, e.g. Sunrise and Sunset.
2. On the other hand, it cannot be ‘Slid for sure when certain changes will recur after one occurrence. Even if they recur, the time interval is not fixed. Such changes are called non-periodic changes, e.g. A meteor streaking across the sky.

Question 8.a.
Which changes shown in the pictures below are temporary.

Answer:
(b) Removing iron nails with help of magnet
(d) Conversion of ice cubes into water.

Question b.
Which of the changes are permanent?
Answer:
Bud blooming into flower.

Question c.
In which did the original matter undergo a change?
Answer:

1. In permanent change
2. Bud blooming into flower.

Question d.
In which the original matter remain unchanged?
Answer:
In temporary changes
(b) iron nails
(d) ice cubes.

Question e.
In which of the changes was a new substance with a new property formed?
Answer:

1. Bud blooming into flower.
2. Ice to water, Ice is in solid state, Water is in liquid state.

Question 9.
Give some examples of fast and slow changes that occur in your surroundings.
Answer:

Fast	Slow
1. Burning of paper or wood	1. rusting of iron
2. Burning of candle	2. germination of seeds
3. Bursting of a balloon	3. curdling of milk
4. Bursting of crackers	4. ripening of a fruit

7th Std Science Questions And Answers:

• Cell Structure and Micro-organisms Class 7 Questions And Answers
• The Muscular System and Digestive System in Human Beings Class 7 Questions And Answers
• Changes – Physical and Chemical Class 7 Questions And Answers
• Elements, Compounds and Mixtures Class 7 Questions And Answers
• Materials We Use Class 7 Questions And Answers
• Natural Resources Class 7 Questions And Answers
• Effects of Light Class 7 Questions And Answers
• Sound: Production of Sound Class 7 Questions And Answers
• Properties of a Magnetic Field Class 7 Questions And Answers
• In the World of Stars Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 2 The Living World Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 2 The Living World Question Answer Maharashtra Board

Class 6 Science Chapter 2 The Living World Question Answer Maharashtra Board

1. Write the answers to the following questions in your words. 

Question a.
What are the differences between plants and animals?
Answer:

Plants	Animals
1. Plants cannot move from one place to another. They are anchored to the soil.	1. Animals can move from one place to another.
2. Plants prepare their own food with the help of chlorophyll and sunlight.	2. Animals cannot prepare their own food. They move in search of food from one place to another.
3. Plants grow throughout their life.	3. Animals grow only up to a certain period of their life.
4. Plants respire with the help of microscopic pores present on their leaves and stems.	4. Animals respire with the help of special organs like lungs, gills, trachea, etc.
5. Plants excrete their waste by storing them in the leaves and bark of plants and then shedding them seasonally.	5. Animals excrete their waste with the help of special organs regularly.
6. Plants are only living things which take in carbon dioxide and give out oxygen during photosynthesis.	6. Animals take in oxygen and give out carbon dioxide throughout their life.
7. Plants reproduce with the help of seeds, stems, spores, bulbs etc.	7. Animals reproduce by laying eggs or giving birth to young ones.

Question b.
What are the similarities between plants and animals?
Answer:

1. Both plants and animals increase in height, size and weight as they grow into an adult.
2. They require food to supply energy to carry out the various life processes.
3. They have a fixed life span after which they die.
4. All plants and animals respire and they take in oxygen and give out carbon dioxide while breathing.
5. All the plants and animals excrete their wastes produced in their body.
6. All plants and animals have ability to reproduce.
7. All plants and animals show responsiveness to their external stimuli.

Question c.
How is the plant kingdom useful to us?
Answer:

1. Plants are used for household as well as industrial purposes.
2. They provide us with food in the form of fruits, vegetables etc., e.g. Potato, methi, bhendi, apple, mango, etc.
3. Some plants are also used as medicines e.g. Adulsa, Hirada, Tulsi etc.
4. They also support birds which build their nests.
5. Wood of tress like oak, fir, birch, etc. are used to make furniture, in building homes, etc. Wood pulp is used to make paper.

Question d.
How is the animal kingdom useful to us?
Answer:

1. Dogs, cats, cows, etc. are domesticated. Dogs and cats are used as pets.
2. Cows, buffaloes, goats, etc. are used for getting their milk.
3. Sheep is used for obtaining wool.
4. Horses, oxen, camels and donkeys are used to carry burden and for various other occupations.
5. Earthworm is useful in agriculture.
6. Birds like hens, turkeys, and ducks provide their eggs to us for food.
7. Insects like bees provide us with honey, silkworm provides us with silk.

Question e.
What makes living things different from non-living things?
Answer:

Living Things	Non-Living Things
1. Living things can grow on their own in size, height and weight.	1. Non-living things do not grow on their own in size, height and weight.
2. Living things can move from one place to another on their own.	2. Non-living things can move only if someone moves them.
3. Living things can reproduce.	3. Non-living things cannot reproduce.
4. Living things exhibit responses to various stimuli.	4. Non-living things do not exhibit responses to various stimuli.
5. They require food for their growth.	5. They do not require any food.

2. What helps them to breathe?

Question a.
(a) A fish (b) A snake (c) A crane (d) An earthworm (e) Man (f) A banyantree (g) A caterpillar.
Answer:

Plant/Animal	Breathing Organ
A fish	gills
A snake	external nostrils and lungs.
A crane	external nose and air sacs in lungs.
An earthworm	moist skin.
Man	nose and lungs.
A banyan tree	microscopic pores (called stomata) present on leaves.
A caterpillar	trachea which opens at the side in their skin.

3. Fill in the blanks with the proper words from the brackets.
(plants, oxygen, dies, excretion, carbon- dioxide, photosynthesis, stimuli, cells, sunlight, chlorophyll, microscopic pores, responsiveness.)

Question a.
The process by which plants make their own food is called ……………… .
Answer:
photosynthesis

Question b.
To inhale …………. and to exhale ……………. is called respiration.
Answer:
oxygen, carbon-dioxide

Question c.
The elimination of waste substances fr6m the body is called ………….. .
Answer:
excretion

Question d.
The ability to respond to an event is called ……….. to ………… .
Answer:
responsiveness, stimuli

Question e.
On completing their lifespan, every living thing ………….. .
Answer:
dies

4. Write the uses of these animals and plants.
Animals: Honeybees, sharks, yaks, sheep, earthworms, dogs, bivalves, horses, mice.
Plants: Ginger, mango, eucalyptus, babul (acacia), teak, spinach, aloevera, turmeric, holy basil, karanja, moh, mulberry, grapevine.

Question a.
Write the uses of these animals and plants.
Answer:

Animals Uses:

Animals	Uses
1. Honeybees	Honey and wax prepared by them is used by us. Beeswax is used in cosmetics like lip – balm, lipgloss, etc.
2. Sharks	The ‘shark liver oil’ obtained from them is a rich source of vitamins.
3. Yaks	Milk and meat obtained is used as food. Yaks are also used for carrying loads in mountainous regions.
4. Sheep	Their fleece is used as a good source of wool. Their meat is used as food.
5. Earthworms	They convert biodegradable waste to good manure (vermicompost)which can be used in fields and gardens. They are called “friends of farmers” as they make the soil fertile.
6. Dogs	They are used as pets to guard houses and farms.
7. Bivalves	Bivalves like oysters are used to obtain pearls used in jewellery making. They are also used as food.
8. Horses	They are used for pulling carriages, heavy loads and also as means of transport in mountainous regions.
9. Mice	They are used in research to test medicines, vaccines etc.
10. Rabbits	They are used as pets and also in research. Their meat is used as food.

Plants Uses:

Plants	Uses
1. Ginger	Used as medicine to cure digestive problems of stomach. It is also used as a spice in food.
2. Mango	It is used to prepare pickles when raw and as a fruit when ripe. It is also used to prepare jam, jelly and in ice-creams.
3. Eucalyptus	Leaves and oil extracted from it is used as medicine to cure fever, cold and cough.
4. Babul (Acacia)	It is used as a medicine. Also used as cattle feed. It is used to clean teeth. It was also used to cure leprosy and heal wounds.
5. Teak (Sag)	Its wood is used to make furniture.
6. Spinach (Palak)	It is used as a vegetable.
7. Aloe vera (Korphad)	It is used to treat various skin diseases. Its gel is used as a moisturizer for skin and for treating hair fall.
8. Turmeric	It is used as a spice and has medicinal properties. It is used for healing wounds and cuts due to its antiseptic properties (i.e. helps to prevent growth of bacteria).
9. Holy basil (Tulsi)	It is used as medicine to cure cough and cold. It also reduces air pollution and drives away mosquitoes.
10. Karanja (Jatropha)	It is used as a medicine and its seeds are used to prepare biodiesel.
11. Moh (Mahwa) [Scientific name: Madhuca longifolia]	The fat extracted from its seeds is used in the manufacture of soaps and detergents. Its bark and flowers are used as medicine. Its leaves are used to feed silkworms which produce Tussar silk. Seeds and flowers are also used to make wine.
12. Mulberry	The leaves of these trees are used for feeding silkworms which produce silk. The fruits are rich in vitamins. Jam and jelly are also made from these fruits.
13. Grapevine	Grapes are fruits of a grapevine. They are used for making jam, jelly, juice, wine and are also eaten as fruits. Raisins are prepared from these grapes.

5. What are the peculiarities of the movements of these living things?
Living things : Snakes, tortoises, kangaroos, eagles, chameleons, frogs, gulmohur, sweet potato creeper, dolphins, ants, rattlesnakes, grasshoppers, earthworms.

Question a.
What are the peculiarities of the movements of these living things?
Answer:

1. Snakes	They don’t have legs. They move in a S-shaped wavy motion. They cannot move over smooth surface. They move by contraction and relaxation of their body muscles.
2. Tortoises	They are very slow and they walk on their four legs by raising their body off the ground. They are the slowest animals.
3. Kangaroos	The hind legs of kangaroos are long and front legs are short. A kangaroo moves by hopping (jumping) on its muscular hind legs with the support of long tail outstretched behind. This movement is called penta pedal movement [Penta = 5, pedal = legs].
4. Eagles	Eagles fly at great heights and they can lift and fly away with prey which are heavier than them. Wings of eagles are strong and powerful.
5. Chameleons	Chameleons can change the colour of their skin and camouflage (hide) in their surroundings. They move slowly with their four legs. They also use their tail and claws to grab a branch and balance themselves.
6. Frogs	Their hind legs are long and front legs are short. Hence, they hop on their hind legs, when on land, and swim with the help of hind limbs when in water.
7. Gulmohar	Gulmohar blooms in summer and the flowers which are red in colour reveal very few leaves. Their leaves fold up during evening. It grows to a height of 5 m to 12 m and it shed all its leaves in dry season.
8. Sweet potato creeper	Sweet potato creepers are fastest growing creepers that cover the whole ground. If they find some support, they try to bend towards it.
9. Dolphins	They move on surface of water by slapping their tail, exposing their head, leaping out of water, diving in the water and doing a side flop. 30 patterns are seen in their behaviour while moving on water.
10. Ants	The ants move in a line and as they move, they leave a chemical called pheromone behind as a trail which attracts other ants. They have six legs and they can walk very fast.
11. Rattle snakes	Rattle snake is a highly poisonous snake. The rattling sound is made by the shaking of the rattle located on its tail when it moves.
12. Grasshoppers	They are insects with three pairs of walking legs and two pairs of wings which helps them to walk, fly and jump. They can leap vigorously due to powerful hind legs.
13. Earthworms	Each segment on the body of earthworm contain group of bristles (called setae) which are used for movement. They move forward by repeated contractions and relaxations of their muscles. A slimy substances secreted by the earthworm helps in its movement.

6. Write in detail about how the plants and animals found in your surroundings prove useful or harmful.

Question a.
Write in detail about how the plants and animals found in your surroundings prove useful or harmful.
Answer:
Some animals and plants around us are harmful to man.

1. Mosquitoes and flies spread diseases.
2. Cockroaches, mice, rats destroy our food. Lice, ticks also spread diseases.
3. The bites of some poisonous lizards, spiders, snakes and scorpions can even cause death.
4. If wild elephants enter human settlements, they cause a lot of destruction.
5. Dog bite from a rabid dog can cause rabies.
6. Plants like datura are poisonous. Consumption of its seed can cause death.
7. Uncontrolled growth of algae and fungi pollutes water and may cause disease. Fungi cause rotting of food.
8. Pods of nettle and colocasia leaves can cause itching.
9. Weeds like parthemum, dodder affect crop growth.

Activity:

Class 6 Science Chapter 2 The Living World Question Answer Question 1.
Obtain information about the work of the Botanical Survey of India and the Zoological Survey of India by visiting the websites :
www.bsi.gov.in, W.zsi.gov.in

Class 6 Science Chapter 2 The Living World Question 2.
Collect information about the lifespan of various animals, make a chart and display it in your class.

The Living World Class 6 Questions And Answers Question 3.
Gather information about the poisonous snakes found in India and present it in a Science Exhibition.

Class 6 Science Chapter 2 The Living World Important Questions and Answers

Fill in the blanks with the proper words from the brackets.
(plants, cells, sunlight, chlorophyll, microscopic pores.)

The Living World Class 6 Question Answers Question 1.
Living things are made up of small units called ……….. .
Answer:
cells

The Living World Class 6 Question 2.
A potted plant placed in a window grows towards ………… .
Answer:
sunlight

The Living World Class 6 Solutions Question 3.
Plants appear green in colour due to the presence of ………… .
Answer:
chlorophyll

The Living World Class 6 Exercise Answers Question 4.
Plants respire by means of ………….. on their stems and leaves.
Answer:
microscopic pores

My Living World Book Class 6 Answers Question 5.
……………….. grow throughout their lifespan.
Answer:
Plants

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Responsiveness to stimuli	a. plants shed leaves in Autumn
2. Respiration	b. seeds sprout when sowed in soil
3. Excretion	c. petals of lotus close when sun sets
4. Reproduction	d. oxygen is taken in through moist skin in earthworms.

Answer:

Column ‘A’	Column ‘B’
1. Responsiveness to stimuli	c. petals of lotus close when sunsets
2. Respiration	d. oxygen is taken in through moist skin in earthworms.
3. Excretion	a. plants shed leaves in Autumn
4. Reproduction	b. seeds sprout when sowed in soil

Plants carry out photosynthesis to prepare their food. With reference to this process of photosynthesis, match the columns given below.

Question 1.

Column ‘A’	Column ‘B’
1. Minerals	a. given out into the air
2. Carbon dioxide	b. absorbed from the soil
3. Heat from sunlight	c. absorbed from the air
4. Oxygen	d. absorbed by chlorophyll.

Answer:

Column ‘A’	Column ‘B’
1. Minerals	b. absorbed from the soil
2. Carbon dioxide	c. absorbed from the air
3. Heat from sunlight	d. absorbed by chlorophyll.
4. Oxygen	a. given out into the air

Can you tell?

Question 1.
What differences do you see between the young ones and the adults in the picture?
Answer:

Answer:
The young ones are smaller in size, height and shape.

Question 2.
What do we learn from these pictures?

Answer:
We learn that all living beings whether plants or animals reproduce in different ways.

Question 3.
Observe a honeycomb and a wall. What are they made up of?
Answer:
Bricks are laid one over the other to form a wall. In a honeycomb, the beeswax is joined to form small compartments to form a honeycomb.

Question 4.
In what ways are the plants and animals useful to us?
Answer:

Plants	Animals
1. Plants cannot move from one place to another. They are anchored to the soil.	1. Animals can move from one place to another.
2. Plants prepare their own food with the help of chlorophyll and sunlight.	2. Animals cannot prepare their own food. They move in search of food from one place to another.
3. Plants grow throughout their life.	3. Animals grow only up to a certain period of their life.
4. Plants respire with the help of microscopic pores present on their leaves and stems.	4. Animals respire with the help of special organs like lungs, gills, trachea, etc.
5. Plants excrete their waste by storing them in the leaves and bark of plants and then shedding them seasonally.	5. Animals excrete their waste with the help of special organs regularly.
6. Plants are only living things which take in carbon dioxide and give out oxygen during photosynthesis.	6. Animals take in oxygen and give out carbon dioxide throughout their life.
7. Plants reproduce with the help of seeds, stems, spores, bulbs etc.	7. Animals reproduce by laying eggs or giving birth to young ones.

Use your brainpower!

Question 1.
What differences do you see in the growth of trees like mango, banyan and peepal and that of bamboo, coconut and toddy palms?
Answer:

1. Trees like mango, banyan and peepal have lot of branches and leaves.
2. They have a thick and wide trunk which is short.
3. Trees like bamboo, coconut and toddy palm have few leaves and they are found only at the top of the trunk.
4. The trunk of the tree is tall and comparatively thin.

Question 2.
In each of the examples given below, what is the stimulus? What is the response?

Answer:

1. In mimosa plant, touching the leaf is the stimulus and closing of mimosa leaves is the response.
2. Keeping the potted plant near the window is the stimulus and growing the stem in the direction of sunlight is the response.

Question 3.
What is the main difference between movements of plants and animals?
Answer:

1. Movement in plants is restricted i.e branches can bend towards light.
2. They swing to and fro when the wind blows.
3. The leaves open or close during the day and night, petals of flowers close or open during night and day.
4. Roots grow in the direction of water under the ground.?
5. Animals can freely move from one place to another in search of food, habitat and shelter.

Question 4.
Why have so many plants and animals been able to survive on the earth even today?
Answer:

1. All the animals and plants have ability to reproduce young ones similar to themselves.
2. Also they have ability to adjust themselves to the conditions in their surroundings.
3. Due to this ability we have so many types of plants and animals and they have been able to survive on the earth even today.

Question 5.
What is the sticky substance seen on the stems of the babul (acacia) or drumstick trees?
Answer:

1. It is the gum which oozes out when we prick it or cut it.
2. It is the waste product that is stored in the bark.
3. This gum has a lot of medicinal value.

Observe and discuss.

Question 1.
Hold your hand in front of your nose or keep your hand on your chest. What do you feel?

Answer:

Living Things	Non-Living Things
1. boy, girl, hen, dog, tree.	1. ball, book, fan, house, bucket, kite.

Find the life span and age of maturity of the given living beings.

Question 1.
Find the life span and age of maturity of the given living beings.
Answer:

Plants/Animals	Life span	Maturity age (Time period required to grow into adults and reproduce)
Dog	10 -15 years	2-3 years
Cow	15 years	2 years
Hen/Chicken	6-8 years	6 months
Elephants	40-60 years	10-15 years
Tortoise	More than 100 years	10-13 years
Butterfly	2-6 weeks	1 week
Mango tree	25 years	3-4 years
Peepal tree	150 years	3-4 years
Banyan tree	200-1000 years	5-6 years
Banana	25 years	3-4 years
Rice	3-4 months	1-2 months
Rose	5-7 years	1 year

Answer the following:

Question 1.
Is all the food we eat used by the body?
Answer:
No, non-essential and undigested food is thrown out of the body in the form of waste.

Question 2.
What is the unused part of food converted into?
Answer:
The unused part of food is converted into excreta.

6th Std Science Questions And Answers:

• Natural Resources – Air, Water and Land Class 6 Questions And Answers
• The Living World  Class 6 Questions And Answers
• Diversity in Living Things and their Classification Class 6 Questions And Answers
• Disaster Management Class 6 Questions And Answers
• Substances in the Surroundings – Their States and Properties Class 6 Questions And Answers
• Substances in Daily Use Class 6 Questions And Answers
• Nutrition and Diet Class 6 Questions And Answers
• Our Skeletal System and the Skin Class 6 Questions And Answers
• Motion and Types of Motion
• Force and Types of Force Class 6 Questions And Answers

Balbharti Maharashtra State Board Class 8 Science Solutions Chapter 19 Life Cycle of Stars Notes, Textbook Exercise Important Questions and Answers.

Std 8 Science Chapter 19 Life Cycle of Stars Question Answer Maharashtra Board

Class 8 Science Chapter 19 Life Cycle of Stars Question Answer Maharashtra Board

1. Search and you will find:

Question a.
Our galaxy is called ………… .
Answer:
Our galaxy is called the Milky Way and Mandakini.

Question b.
For measuring large distances, ………… is used as a unit.
Answer:
For measuring large distances, the light year is used as a unit.

Question c.
The speed of light is …………. km/s.
Answer:
The speed of light is 300000 km/s.

Question d.
There are about ………… stars in our galaxy.
Answer:
There are about 100 billion stars in our galaxy.

Question e.
The end stage of the Sun will be …………. .
Answer:
The end stage of the Sun will be a white dwarf.

Question f.
Stars are born out of ………… clouds.
Answer:
Stars are born out of interstellar clouds.

Question g.
Milky way is a ………. galaxy.
Answer:
Milky way is a spiral galaxy.

Question h.
Stars are gigantic spheres of ………… gas.
Answer:
Stars are gigantic spheres of hot gas.

Question i.
The masses of other stars are measured relative to the mass of the …………. .
Answer:
The masses of other stars are measured relative to the mass of the Sun.

Question j.
Light takes ……………. to reach us from the Sun while it takes …….. to reach us from the moon.
Answer:
Light takes about 8 minutes to reach us from the Sun while it takes about 1 second to reach us from the moon.

Question k.
The larger the mass of a star, the faster is its ……….. .
Answer:
The larger the mass of a star, the faster is its evolution.

Question l.
The number of fuels used in the life of a star depends on its …………. .
Answer:
The number of fuels used in the life of a star depends on its mass.

2. Who is telling lies?

Question a.
Light year is used to measure time.
Answer:
False. (Light year is used to measure distance.)

Question b.
End stage of a star depends on its initial mass.
Answer:
True.

Question c.
A star ends its life as a neutron star when the pressure of its electrons balances its gravity.
Answer:
False. (A star ends its life as a neutron star when the pressure of its neutrons balances its gravity.)

Question d.
Only light can emit from the black hole.
Answer:
False. (Not even light can be emitted by a black hole.)

Question e.
The Sun will pass through the supergiant stage during its evolution.
Answer:
False. (The Sun will pass through the red giant stage during its evolution.)

Question f.
The Sun will end its life as a white dwarf.
Answer:
True.

3. Answer the following question:

Question a.
How do stars form?
Answer:
There are huge clouds of gas and dust in the empty spaces between the stars in a galaxy. These clouds are called interstellar clouds. The size of an interstellar cloud is about a few light years.

When an interstellar cloud starts contracting due to some disturbance, its density and temperature increase. This results in formation of a dense sphere of hot gas and nuclear energy generation starts at the centre of the star. Therefore, the gas sphere becomes self-luminous. Thus a star is formed, i.e., a star is born.
A huge interstellar cloud can produce thousands of stars at a time.

Question b.
Why do stars evolve?
Answer:
Although stars appear stable for quite a long period of time, their properties do change, though very slowly. A change in the properties of a star, leading to its passing through different stages, is called evolution of the star. Burning of the fuel at the centre of the star and a gradual decrease in its amount is the main reason of evolution of a star.

Question c.
What are the three end stages of stars?
Answer:

1. Stars having initial mass less than 8 times the mass of the Sun ultimately become white dwarfs.
2. Stars having initial mass between i 8 and 25 times the mass of the Sun ultimately become neutron stars.
3. Stars having initial mass larger than 25 times the mass of the Sun ultimately turn into black holes.

Question d.
Why was the name black hole given?
Answer:
When a star having initial mass larger than 25 times the mass of the Sun reaches its end stage, its gravitational force and density increase exponentially. All nearby objects get attracted towards the star and nothing can come out of it, not even light. All incident light is absorbed by the star. We can probably see a very minute black hole at its place. Hence, the name is given as black hole.

Question e.
Which types of stars end their life as a neutron star?
Answer:
Stars having initial mass between 8 and 25 times the mass of the Sun end up as neutron stars. When these stars pass through ( the supergiant stage, their size increases to 1000 times. Huge explosion that occurs in the last stage of these stars is very powerful and very high energy is given off. After the huge explosion, called the supernova explosion, their central portion contracts in size to about 10 km. In this stage, such stars are completely made up of neutrons and hence are called neutron stars.

4. A. If you are the Sun, write about your properties in your own words.
B. Describe white dwarfs.

Question A.
If you are the Sun, write about your properties in your own words.
Answer:

If you are the Sun, write about your properties in your own words.
Answer:
There are billions of stars in the galaxy called the Milky Way and Mandakini. I am one of the small stars called the Sun. I have my own family called the solar system. There are planets, satellites, asteroids, comets and meteors in my family. My mass is 2 × 1030 kg which is about 3.3 lakh times that of the earth. With a radius of 695700 km, my size is about 100 times that of the earth. My surface temperature is about 5800 K while it is 1.5 × 107 K at the centre.

72 % of my mass consists of hydrogen while 26 % consists of helium. Rest 2 % is made up of elements heavier than helium. I am about 4.5 billion years old and the scientists on the earth have concluded that not much change has taken place in my properties during this period. According to the scientists, in the end stage of my life, I will turn into a red giant star. Thereafter, I will first explode and then contract to become as small as the earth. I will appear small as well as white and hence, I will be called a white dwarf. This will be my last stage for ever.

Question B.
Describe white dwarfs.
Answer:
Depending on the initial mass, stars can reach one of the three end stages. White dwarf is one such stage of stars having initial mass less than 8 times the mass of the Sun. These stars undergo huge expansion and their radius increases by a factor of 100 to 200. These stars appear reddish because of their large size and lower temperature. Hence, these stars are also called red giant stars.

At the end of their evolution, these stars explode, their outer gas envelope is thrown outward and the inner part contracts to the size of the earth. However, the density in the star becomes very high. In this stage, the pressure due to electrons becomes independent of temperature and sufficient to balance the gravitational force for ever.

In this stage, such stars look white and due to their small size they are called white dwarfs.

Can you recall?

Question 1.
What is a galaxy?
Answer:
A system of billions of stars, their planetary systems and interstellar clouds of gas and dust held together by gravitational attraction is called a galaxy.

Question 2.
What are the different constituents of our solar system?
Answer:
The different constituents of our solar system are as follows :

1. Sun as a star.
2. Eight planets, namely, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune; of which Mercury, Venus, Earth and Mars are made up of rocks and minerals, while Jupiter, Saturn, Uranus and Neptune are made up of gases.
3. Natural satellites of some planets revolving around the respective planets.
4. Asteroids located between Mars and Jupiter.
5. Comets made up of ice, dust and gases.
6. Meteors and meteoroids.

Question 3.
What are the major differences between a star and a planet?
Answer:

1. Nuclear/atomic explosions regularly take place at the centre of stars. This causes the discharge of heat and light. Hence, stars shine. Planets do not discharge any light. They are visible due to the light reflected by them.
2. Stars are very big in size and massive relative to planets.
3. Stars twinkle, planets do not.
4. Stars are made up of hydrogen, helium and other light elements.
5. Planets are made up of solid, liquid or gaseous substances or a combination thereof.

Question 4.
What is a satellite?
Answer:
An astronomical object orbiting a planet is called a satellite.

Question 5.
Which is the star nearest to us?
Answer:
The star nearest to us is the Sun.

Project:

Question 1.
Use your imagination and make models of the Milky Way and the solar system.
Answer:
N.B. Students can make these models and display the same in science exhibition. You can use sand, scrap material, stones, pebbles, marbles, pieces of glass, beads, etc.

Question 2.
Write the effects: If the Sun disappears ………..
Answer:
N.B. You can write the effects with the help of the following points:

1. No sunrise, no sunset, no beauty of morning and evening wee hours.
2. In the absence of the gravitational force due to the Sun, the earth will drift away in the galaxy.
3. Darkness, no source of energy, end of life on the earth.
4. Moon will be invisible.
5. The temperature of the earth will fall below the freezing point of water. All oceans will also freeze.
6. Even the atmosphere will freeze and fall on the earth. This will cause more cosmic rays to reach the earth.

Class 8 Science Chapter 19 Life Cycle of Stars Important Questions and Answers

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Gravitational force	a. Alpha Centauri
2. The star nearest to us other than the Sun	b. 2 × 1030 kg
3. Mass of the Sun	c. 10 30 g
	d. towards the centre of a star or a planet

Answer:

Column ‘A’	Column ‘B’
1. Gravitational force	d. towards the centre of a star or a planet
2. The star nearest to us other than the Sun	a. Alpha Centauri
3. Mass of the Sun	b. 2 × 1030 kg

Question 2.
Mass of the star:

Column ‘A’	Column ‘B’
1. < 8 MSun	a. Proton star
2. between 8 and 25 times MSun	b. Black hole
3. > 25 MSun	c. Neutron star
	d. White dwarf

Answer:
Mass of the star:

Column ‘A’	Column ‘B’
1. < 8 MSun	d. White dwarf
2. between 8 and 25 times MSun	c. Neutron star
3. > 25 MSun	b. Black hole

Answer the following questions in one sentence each:

Question 1.
Name the star nearest to the earth.
Answer:
The Sun.

Question 2.
Other than the Sun, which is the star nearest to the earth?
Answer:
Alpha Centauri.

Question 3.
What would be the last stage of the Sun?
Answer:
The last stage of the Sun would be white dwarf.

Question 4.
Name two forces that act on any star.
Answer:
Gravitational force and the force due to the pressure of hot gas are the two forces that act on any star.

Question 5.
What is a black hole?
Answer:
A black hole is the end stage of a quite big star, where due to the extremely high gravitational force, nothing, not even light, comes out.

Answer the following questions:

Question 1.
How is stability of stars maintained?
Answer:
Properties of a star remain unchanged for quite a long time. The gravitational force and the force due to the pressure of the hot gas act together on a star. The gravitational force acts towards the centre of the star and tries to bring the gas particles close together. Hot gas shows the tendency to spread and its force acts away from the centre of the star. This force tries to disperse the gas particles. A balance between the gravitational force and the force due to the hot gas keeps the star stable.

However, if the magnitude of any one force is more than that of the other force, the star either contracts or expands depending upon which force dominates.

Question 2.
Why is the Sun called an ordinary star?
Answer:
The star nearest to the earth is the Sun. Hence, it appears quite big and bright. There are billions of stars in our galaxy called the Milky Way and Mandakini which are greater or lower in mass, size and temperature than the Sun. Hence, the Sun is called an ordinary star.

Do you know?

When the Sun will become a red giant, its diameter will increase so much that it will swallow Mercury and Venus. It is possible that the earth will also be absorbed by the Sun. It will take about 4-5 billion years for the Sun to reach this state.

Question 3.
Describe various stages of evolution of star.
Answer:
Though the properties of a star remain unchanged for quite a long time, this situation is never static. A star passes through different stages. This process is called the evolution of a star.
Important stages of the evolution of a star are as follows:

1. Initial stage of stability: The gravitational force and the force due to the pressure of the hot gas act together on a star. The gravitational force acts towards the centre of the star and tries to bring the gas particles close together. Hot gas shows the tendency to spread and its force acts away from the centre of the star.

This force tries to disperse the gas particles. A balance between the gravitational force and the force due to the hot gases keeps the star stable, as long as the energy generation continues at the centre of the star.

2. Burning of the fuel: As a star continuously emits energy, its energy constantly decreases. When the fuel at the centre of the star is exhausted, the energy generation stops and the temperature of the star starts decreasing. Decreasing temperature causes the gas pressure to decrease and the balance between the gravitational force and the force due to the gas pressure is no more maintained.

As the magnitude of the gravitational force is now more than that of the force due to the gas pressure, the star starts contracting. This causes another fuel to start burning, e.g. on exhausting hydrogen, helium starts undergoing fusion. Availability of multiple fuels depends on the mass of the star.

The higher the mass of the star, the more is the number of fuels used. The star either contracts or expands during the course of using these fuels. This may cause the imbalance between the gravitational force and the force due to the hot gas.

3. Total exhaustion of the fuel: When all fuels are exhausted, the energy generation in the star finally stops completely and the temperature of the star starts decreasing. The balance between the gravitational force and the force due to the gas pressure can no more be maintained. The evolution of the star ends and the star proceeds to its end stage.

4. End stage of a star: Once the fuel in the star is totally exhausted, the energy generation in the star stops and subsequently the gas pressure decreases, the star starts contracting and its density starts increasing. When the density becomes very high, some new types of pressures are generated which are independent of the temperature of the gas.

In such a case, the pressure remains stable despite low temperature and absence of any energy generation and thus the star remains stable for ever. This stage is the end stage of the star. Depending on the initial mass, stars can reach one of the three end stages.

• Stars having initial mass less than 8 times the mass of the Sun ultimately become white dwarfs.
• Stars having initial mass between 8 and 25 times the mass of the Sun ultimately become neutron stars.
• Stars having initial mass larger than 25 times the mass of the Sun ultimately turn into black holes.

Write short notes on the following:

Question 1.
End stages of stars having initial mass less than 8 times the mass of the Sun.
Answer:
These stars undergo huge expansion and their radius increases by a factor of 100 to 200 during their various stages of evolution. These stars appear reddish due to their lower temperature. Hence, they are called red giant stars.

At the end of evolution, these stars explode, their outer gas envelope is thrown out and the inner part contracts roughly to the size of the earth. Hence, the density of the star becomes very high. In this stage, the pressure due to electrons becomes independent of temperature and sufficient to balance the gravitational force for ever. Such stars look white and due to their small size they are called white dwarfs.

Question 2.
End stage of the stars having mass between 8 and 25 times the mass of the Sun.
Answer:
These stars pass through the red giant stage and later super giant stage, during which their size may increase to 1000 times. The huge explosion, called the supernova explosion, occurs in the last stage of the evolution. It is very powerful and very high energy is given off in this case.

As a result, the stars are visible even during the day. Later their central portion contracts to about 10 km. In this stage, the stars are completely made up of neutrons and are called neutron stars. The pressure of these neutrons is independent of temperature and sufficient enough to balance the gravitational force for ever.

Question 3.
End stages of stars having mass larger than 25 times the mass of the Sun.
Answer:
After the supernova explosion, no pressure can balance the gravitational force. Hence these stars contract continuously and their gravitational force and density increase exponentially. All nearby objects get attracted towards these stars and not even light can come out of them. Light falling on these stars is completely absorbed by the star. We cannot see these stars. A very minute black hole is formed at the place of such a star. This is the end stage of these stars.

8th Std Science Questions And Answers:

• Human Body and Organ System Class 8 Questions And Answers
• Introduction to Acid and Base Class 8 Questions And Answers
• Chemical Change and Chemical Bond Class 8 Questions And Answers
• Measurement and Effects of Heat Class 8 Questions And Answers
• Sound Class 8 Questions And Answers
• Reflection of Light Class 8 Questions And Answers
• Man-made Materials Class 8 Questions And Answers
• Ecosystems Class 8 Questions And Answers
• Life Cycle of Stars Class 8 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 11 Work and Energy Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 11 Work and Energy Question Answer Maharashtra Board

Class 6 Science Chapter 11 Work and Energy Question Answer Maharashtra Board

1. Fill in each blank with the appropriate term from the brackets.

Question a.
A bucketful of water is to be drawn from a well ………. will be done when a ………… is applied to do this, because there will be an ……………. of water.
(displacement, workforce)
Answer:
work, force, displacement

Question b.
If a ball is dropped on the sloping roof of a house, it acquires ……………. and falls on the ground. That is transformation of ………… energy into ……….. energy takes place.
(kinetic, potential, motion)
Answer:
motion, kinetic, potential

Question c.
You might have seen some beautiful fireworks during Diwali. It is an example of transformation of ……….. energy into ………………. energy.
(light, atom, chemical, solar)
Answer:
chemical, light

Question d.
The solar cooker is an application of the ………… energy of the sun, while solar cells, solar lamps are applications of the ………….. energy of the sun.
(light, chemical, heat)
Answer:
heat, light

Question e.
One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance …………. work will be done.
(equal, more, less)
Answer:
equal

Question f.
The capacity that an object has for doing work is called ………… .
(energy, displacement, force)
Answer:
energy

2. Match the pairs.

Question a.

Column ‘A’	Column ‘B’
1. Rolling object	a. Heat energy
2. Food	b. Atomic energy
3. Stretched bow	c. Kinetic energy
4. Sunlight	d. Potential energy
5. Uranium	e. Chemical energy

Answer:

Column ‘A’	Column ‘B’
1. Rolling object	c. Kinetic energy
2. Food	e. Chemical energy
3. Stretched bow	d. Potential energy
4. Sunlight	a. Heat energy
5. Uranium	b. Atomic energy

3. Can you tell?

Question a.
When can we say that displacement has taken place?
Answer:
When the position of an object changes, we say that the object is displaced.

Question b.
What are the various forms of energy?
Answer:
Various forms of energy are: mechanical energy, heat energy, light energy, sound energy, chemical energy and electrical energy.

Question c.
Describe the natural chain of transformation of energy.
Answer:

1. In the course of water cycle, water evaporates due to the heat of the sun.
2. This water vapour forms clouds that give rain.
3. Rainwater flows into rivers and is stored in reservoirs or dams.
4. This stored water at a height has potential energy.
5. As the water falls down, this is transformed into kinetic energy.
6. When the water falls on the turbine, its kinetic energy is transferred to turbine.
7. The turbine rotates producing electrical energy.

Question d.
What should be taken into account for measuring work?
Answer:
For measuring work both force and displacement must be taken into account.

Question e.
Why should we save energy?
Answer:
Due to increasing population and increasing use of energy resources, there is a danger that limited reserves of coal, petrol, etc. will get exhausted. Hence, we should save energy for future generation.

Question f.
What is ‘green energy’?
Answer:
The energy resources which do not produce smoke and carbon gases such as carbon dioxide or carbon monoxide are called ‘green energy resources’. Energy from them is called green energy.

Question g.
What are the non-conventional energy resources?
Answer:
The resources that:

1. have not been used traditionally.
2. are inexhaustible and continuous.
3. That can be used in various forms again and again are called non-conventional energy resources.
4. e.g.: solar energy, wind energy, tidal energy, hydal power.

Question h.
Which forms of energy from the sun is used in solar energy devices?
Answer:

1. Heat energy from the sun is used in solar cookers, solar water heaters, solar driers.
2. Light energy from the sun is used in solar cells, solar panels.
3. Solar electric plants have the capacity to produce electricity on large scale.

Question i.
Why should we maximize the use of non- ntional energy sources?
Answer:

1. Due to increase in population there is increasing use of conventional sources like petrol, coal, etc. Their reserves are limited and they may get exhausted.
2. Hence, it will be better to use non- conventional sources of energy to save conventional resources for future.

4. Who is the odd-one-out?

Class 6 Science Chapter 11 Work And Energy Question 1.
Diesel, crude oil, natural gas, wind.
Answer:
wind

Work And Energy Class 6 Maharashtra Board Question 2.
A running car, hauling a log, a book kept on a table, picking up the school bag.
Answer:
A book kept on table.

Work And Energy Class 6 Question 3.
Sunlight, wind, wave, petrol.
Answer:
Petrol.

11 Work And Energy Class 6 Question 4.
Leaving the fan on in a vacant room, leaving the TV on while working, using A.C during winter, putting off the light when going out.
Answer:
putting off the light when going out.

5. Find out the types of energy from the following puzzle.

Question a.
Find out the types of energy from the following puzzle.

Answer:
Potential, Kinetic, Solar, Wind, Sound, Light, Heat

Activity:

Work And Energy Exercise Class 6 Question 1.
How can you save energy at home and in school? Discuss this with your friends and list all such measures. Put them into practice.

Work And Energy Class 6 Questions Answers Question 2.
Find out about energy saving devices available in the market.

Class 6 Science Chapter 11 Work and Energy Important Questions and Answers

Fill in the blanks with suitable words.

Work And Energy Class 6 Exercise Question 1.
Falling water possesses ………………… energy.
(potential, kinetic, chemical)
Answer:
kinetic

Work And Energy Class 6 Questions And Answers Question 2.
Heat is measured in unit called ……………….. .
(kilometres, kilogram, calorie)
Answer:
calorie

Class 6 Science Chapter 11 Question 3.
Plant stores the food in the form of ……………….. energy.
(mechanical, light, chemical)
Answer:
chemical

11. Work And Energy Class 6 Question 4.
We should use ……………….. energy resources with care.
(conventional, non-conventional, both)
Answer:
conventional

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Solar energy	a. Waves
2. Tidal energy	b. Home cooking
3. Natural gas	c. Car
4. Petrol	d. Solar water heater

Answer:

Column ‘A’	Column ‘B’
1. Solar energy	d. Solar water heater
2. Tidal energy	a. Waves
3. Natural gas	b. Home cooking
4. Petrol	c. Car

Can you tell?

6th Science Work And Energy Question 1.
Water in dams or reservoirs shows potential energy.
Answer:
Rainwater flows into river and is stored in reservoirs on dams. These are at height and therefore, their water has potential energy.

Class 6 Science Chapter 11 Question Answer Question 2.
The sun is the most important source of all energy.
Answer:
All forms of energy are utilizing indirectly solar energy in all transformation of energy. Therefore, the sun is the most important source of all energy.

Question 3.
What is tidal energy?
Answer:
A wall is constructed at a narrow region of a creek. Due to waves generated by high and low tides, the turbine of the generator fitted in the wall starts rotating and electricity is generated.

Use your brain power!

Question 1.
Why do you get hungry after physical exercise?
Answer:

1. When we do physical exercise we use the energy stored in the body.
2. To replenish this energy, we have to eat. Hence we feel hungry.

Question 2.
From where does our body get energy.
Answer:
Our body gets energy from the food we eat.

Question 3.
Why do we get tired?
Answer:
When we do any work, we use the energy. If this energy level becomes very low, then we feel tired.

Question 4.
What is the unit of work and energy?
Answer:
The unit of work and energy in SI (System International) is ‘Joule’.

Question 5.
If no displacement occurs on applying a force, what does it indicate?
Answer:
If no displacement occurs, then no work is said to be performed.

Can you tell?

Question 1.
In the game of marbles, from where does one marble get energy to set another marble in motion?
Answer:
When we apply physical force to the fast marble, it gains some force and when it strikes the second marble, energy in the form of force is transferred to the second marble and this force sets the second marble in motion.

Question 2.
While playing carrom from where does the striker gets the energy to make the pieces move?
Answer:
When we strike the striker, the force exerted by our muscles is transferred to the striker. When the striker strikes the coin, this energy is transferred to the coin which may help to pocket the coin.

Question 3.
What will happen as result of the action in the picture?

Question i.
The rubber band is released after streaching it.
Answer:
It comes back to its orriginal position.

Question ii.
A stone is held in the rubber of a catapult, the rubber is stretched and released.
Answer:
Stone gets thrown to a distance and rubber band cones back to its original position.

Let’s try this.

Question 1.
If we hold a convex lens over a sheet of paper in sunlight such that there is tiny spot of light on the paper for a while. What happens? Why?
Answer:

1. If a convex lens is held over a paper in sunlight such that there is a tiny spot of light on the paper for a while the paper bums.
2. This is due to the heat energy of the sun concentrated at a point due to the convex lens.

Question 2.
How does a picture appear on the screen of a TV?
Answer:
When a TV is switched on, the electrical energy is converted into light and sound energy. Hence, a picture appears on TV.

Question 3.
In which form is energy stored in plant food?
Answer:
Energy stored in plant food is in the form of chemical energy.

Question 4.
How is energy obtained from cooking gas?
Answer:
Energy obtained from cooking gas is heat energy which is obtained by conversion of chemical energy.

Question 5.
Why is Energy not visible to us?
Answer:
Energy is the capacity to do work. Energy is converted from one form to another in the form of work being done. Hence it is not visible to us.

How are we different from each other?

Question 1.
Potential energy and Kinetic energy
Answer:

Potential energy	Kinetic energy
1. Energy stored in an object due to its position is called potential energy.	1. Energy possessed by a body due to its motion is called kinetic energy.
2. No work is performed.	2. Work is performed.

Question 2.
Work and energy
Answer:

Work	Energy
1. When an object is displaced by applying force on it, work is said to be done.	1. Energy is the capacity to do work.
2. Work is done as a result of using energy.	2. Energy is the cause for work to be done.

Question 3.
Conventional and Non-conventional energy sources
Answer:

Conventional source of energy	Non-Conventional source of energy
1. Man has been using these energy resources for centuries.	1. These resources have not been used traditionally.

Classify as directed:

Question 1.
Into kinetic and potential energy
Waterfalls, water in a reservoir, a stretched spring, a boy running in a race.
Answer:

• Potential – water in a reservoir, a stretched spring.
• Kinetic – waterfalls, a boy running in a race.

Question 2.
Into conventional and non-conventional energy sources.
Tidal energy, diesel, cooking gas, coal, hydropower, solar energy.
Answer:

• Conventional energy sources – diesel, cooking gas, coal.
• Non-conventional energy sources – tidal energy, hydropower, solar energy.

Question 3.
Into different forms of energy

1. rubber band is released
2. cooking food
3. switching on fan
4. a battery
5. radio
6. TV

Answer:

1. Mechanical energy
2. Heat energy
3. Mechanical energy, electrical energy
4. Chemical energy
5. Sound energy
6. Light and sound energy

Define:

Question 1.
Work
Answer:
When an object is displaced by applying a force on it, work is said to be done.

Question 2.
Energy
Answer:
Energy is the capacity to do work.

Question 3.
Chemical energy
Answer:
The energy obtained through chemical action is called chemical energy.

Question 4.
Potential energy
Answer:
The energy which is stored in an object due to a specific state or position of that object is called potential energy.

Question 5.
Kinetic energy
Answer:
The energy obtained by the virtue of its motion is called kinetic energy.

Question 6.
Solar energy
Answer:
The enormous and continuous energy obtained from the sun is called solar energy. Solar energy is at the root of all energy available on earth.

Question 7.
Conventional energy resources: (non-renewable energy sources)
Answer:
The energy sources which man has been using for centuries and that cannot be replenished are called conventional energy sources.

Question 8.
Renewable energy sources: (non – conventional energy sources)
Answer:
The resources that have not been used traditionally and that are inexhaustible, continuous and can be used in various forms again and again are called renewable energy sources.

Explain – why?

Question 1.
Energy is not visible to us.
Answer:
There is energy in every substance in the universe. It is present in non-living as well as living things. But still we can only feel the energy when some work is done, e.g. When wind blows, we can feel the coolness in air. When we switch on the light in a dark room, we can see things due to light energy.

Question 2.
Save energy, (use alternative energy sources)
Answer:

1. Due to increasing population, there is increasing usage of energy resources.
2. There is a danger that limited reserves of conventional resources like diesel, crude oil, may get exhausted.
3. We should save energy so that future availability is ensured.
4. It will be better to use alternative and supplementary energy sources.

Question 3.
Methods of saving energy.
Answer:

1. Saving energy is as good as generating energy.
2. There are several ways of saving energy such as putting off lamps when not needed.
3. Making maximum use of sunlight.
4. Saving energy and energy resources is absolutely necessary. Otherwise, we will have to face the serious calamity like global warming.

Question 4.
State the energy conversions in following cases.

1. Solar water heater
2. Solar cell
3. Fission of uranium, thorium
4. Switch on mixer
5. Switch on lamp
6. Switch on TV
7. Switch on radio
8. Ram plays tabla
9. Ravi plays shehnai
10. You switch on the torch
11. Your mother lights the gas stove to cook
12. Dinesh is bursting crackers during Diwali

Answer:

1. Solar energy to heat energy
2. Solar energy to electrical energy
3. Atomic energy to heat energy and then to electrical energy
4. Electrical energy to mechanical energy
5. Electrical energy to light energy
6. Electrical energy to light energy and sound energy
7. Electrical energy to sound energy,
8. Mechanical energy to sound energy
9. Wind energy to sound energy
10. Chemical energy to light energy
11. Chemical energy to heat energy
12. Chemical energy to heat, light and sound energy

Observe the figure below and answer the question given.

Question i.
In the above activity, which are the different forces acting on the box?
Answer:
In the above activity, muscular force, frictional force and gravitational force act on the box.

Question ii.
Is displacement possible without force?
Answer:
No, force has to be applied in order to displace the box.

Question iii.
If force is applied to both the boxes is same, which box will be displaced more?
Answer:
If force applied to both the boxes is same, then empty box will be displaced more than box with books.

Question iv.
If me e books are added to box, and same force is applied, will the displacement be more or less?
Answer:
If the same force is applied for a heavier load then the displacement will be less.

Question v.a.
If a force is applied with both the hands on a wall, will there be a displacement?
Answer:
Whatever be the amount of force applied, the wall will not be displaced.

Question b.
If no displacement occurs on applying as force, what does it indicate?
Answer:
If no displacement occurs, then no work is said to be performed.

6th Std Science Questions And Answers:

• Work and Energy Class 6 Questions And Answers
• Simple Machines Class 6 Questions And Answers
• Sound Class 6 Questions And Answers
• Light and the Formation of Shadows Class 6 Questions And Answers
• Fun with Magnets Class 6 Questions And Answers
• The Universe Class 6 Questions And Answers

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 17 Effects of Light Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 17 Effects of Light Question Answer Maharashtra Board

Class 7 Science Chapter 17 Effects of Light Question Answer Maharashtra Board

1. Fill in the blanks.

Question a.
When the beams from the headlights of a car fall on an object in the night, the shadows – called ………. and ………… . can be seen.
Answer:
umbra, penumbra

Question b.
During a lunar eclipse the shadow of the …………. falls on the ………. .
Answer:
earth, moon

Question c.
During a solar eclipse the shadow of the ………. falls on the ………… .
Answer:
moon, earth

Question d.
Various shades of colour are seen in the sky at sunrise and sunset due to ……….. .
Answer:
scattering of light

2. Give reasons.

Question a.
Space beyond the earth’s atmosphere appears dark.
Answer:

1. Space beyond the earth’s atmosphere does have some gas and cosmic dust but there is not any atmosphere.
2. As there are no particles to scatter the sunlight, the space appears black.

Question b.
We are able to read while sitting in the shade.
Answer:

1. We are able to read because the sun light which falls on the book is scattered and reaches our eyes.
2. While sitting in the shade our eyes adjust to the environment and to amount of light available. That is how we are able to read.

Question c.
We should not observe the solar eclipse with naked eyes.
Answer:

1. During a solar eclipse ultra-violet rays which are harmful to us reach the earth and may lead to eclipse blindness or retinal bums and cataracts.
2. In order to protect our eyes a solar eclipse should never be watched with the naked eye.
3. A special type of goggles should be used for this.

3. Give some examples of scattering of light that we come across in day to day life.

Question a.
Give some examples of scattering of light that we come across in day to day life.
Answer:

1. The formation of rainbow, shift in position of stars, increased day time, mirage, inverted image, glittering of diamond, the working of lens and prism, bending of pen in water are examples of scattering of light.
2. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.
3. During sunrise and sunset, sunlight has to travel greater distance, so shorter wavelength gets scattered off and removed and only orange and red with longer wavelengths reach us.
4. So during sunrise and sunset, sky appears fed and orange.

4. Why is the shadow of a bird flying high not seen on the earth?

Question a.
Why is the shadow of a bird flying high not seen on the earth?
Answer:

1. Birds flying high in the sky do cast their shadow but because they are shading an area that is very tiny the shadow is not visible.
2. The higher the bird flies, the smaller the shadow it casts.
3. Also when the bird flies high, the dark part of the shadow that is called Umbra does not reach the ground so we do not see its shadow.

5. Why is a penumbra not obtained from a point source?

Question a.
Why is a penumbra not obtained from a point source?
Answer:

1. The umbra, penumbra are the distinct parts of a shadow, created by any light source after striking on an opaque object.
2. For a point source, only the umbra is cast sharp dark shadow and not penumbra, because all the light of the point source will be blocked by any shadowing object.
3. Whereas penumbra forms only when some of the light from the source gets blocked by the shadowing object and not all of it does.

6. Answer the following questions in your own words.

Question a.
What is meant by scattering of light?
Answer:

1. Scattering of light is the deviation of light rays from its straight path.
2. As light propagates through the atmosphere, it travels in a straight path until it is obstructed by bits of dust or gas molecules in the atmosphere
3. The process in which light gets deflected by the particles in the medium through which the light passes is called scattering, e.g. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.

Question b.
Does the shadow really vanish in the zero shadow condition?
Answer:
1. Yes, the day on which the sun reaches exactly overhead, at noon, shadow completely disappears.
‘This event can be seen in the region between the Tropic of Cancer (23.5°N) and Tropic of Capricorn (23.5°S).
2. The shadow diminishes and eventually disappears for a while only to reappear later.

Question c.
Will the laser beam be seen if it passes through a glass box which contains a lighted incense stick?
Answer:
Yes, it will be seen.

7. Discuss and write:

Question a.
Write a science based paragraph on ‘What if the sun did not rise’?
Answer:

1. The sun is a star and the centre of our solar system. Everything in our solar system revolves around the sun.
2. If the sun were to suddenly disappear, Earth and the other planets would retain their forward motion, effectively flying off into outer space in a straight line.
3. If the Sun didn’t rise means the Earth’s rotation had come to a screeching halt.
4. Sunrise and sunset are a result of the earth’s rotation so we will not get to see sunrise or sunset. Earth’s spinning generates the magnetic field at the core and it is saving us from harmful rays from the sun.
5. Without sun it would be very dark. No sun means no plants and no animals. Of course, without sun none of us would even exist.
6. Moon will disappear, because the moon dose not produce light. We only see the moon because sunlight is reflected by the moon.
7. Without the sun’s warmth, Earth would quickly become a much colder place. Life would be difficult, oceans will freeze.
8. Without sun rays, all photosynthesis on earth would stop. All plants would die.
9. All animals that rely on plants for food, including humans would die.

Question b.
What efforts will you make to remove the misconceptions about eclipses?
Answer:
Solar, lunar eclipse have been traditionally observed as an ominous sign and therefore superstitions are prevalent in association with these natural phenomena.
1. All these misconceptions should be removed by explaining scientifically the process of eclipse how it happens: (a) Explain with the help of diagram and models of sun, moon and earth, (b) Explain how special glasses which will protect us from UV rays, and excess heat can be used to observe eclipses safely.
2. Also inform that eclipses are natural phenomena and can be predicted in advance.

Question c.
Various eclipses and the conditions during that period.
Answer:
There are two eclipses:

1. Solar eclipse
2. Lunar eclipse

1. Solar eclipse:
There are two types of Solar eclipse, (a) Total solar eclipse (b) Partial solar eclipse

a. Total solar eclipse: In total solar eclipse, the moon is between the sun and the earth and the moon shadow covers the sun disc fully by perfect alignment. The part of the earth that lies in the umbra of the moon experiences total solar eclipse.

b. Partial solar eclipse: In partial solar eclipse, the moon is between the sun and the earth arid the moon shadow does not cover the sun disc fully, because of imperfect alignment. The part of the earth that lies in the penumbra of the moon experiences partial solar eclipse.

c. The solar eclipse occur on a new moon day.
d. Solar eclipse last for few minutes.

2. Lunar eclipse:
There are two types of Lunar eclipse, (a) Total lunar eclipse (b) Partial lunar eclipse

a. Total lunar eclipse: In total lunar eclipse, the earth comes in between the sun and the moon and the earth’s shadow covers the moon’s surface fully because of perfect alignment.

b. Partial lunar eclipse: In partial lunar eclipse, the earth’s shadow does not cover the moon’s surface fully because of inperfect alignment. A small part of the moon’s surface is covered by umbra part of earth’s shadow.

c. The lunar eclipse occurs on a full moon night.
d. Lunar eclipse last for few hours.

8. Explain the difference:

Question a.
Point sources and Extended sources.
Answer:

Point sources	Extended sources
1. A source of radiation light that is concentrated at a point and considered as having no spatial extension.	1. An extended source is a source consisting of many point sources separated internally.
2. Shadow we get from a point source is dark called umbra.	2. Shadow we get from extended source of light is faint called penumbra and dark called umbra

Question b.
Umbra and Penumbra.
Answer:

Umbra	Penumbra
1. The umbra is a central core of darkness which tapers away.	1. The penumbra is an outer cone of partial shadow which diverges, instead of tapering.
2. Umbra is shadow formed from a point source of light.	2. It is the shadow formed from the extended source of light.
3. It is dark	3. It is faint
4. Umbra is the area of total shadow	4. Penumbra is the area of partial shadow.

Project:

Question a.
Obtain information about the special goggles used to watch a solar eclipse.

Class 7 Science Chapter 17 Effects of Light Important Questions and Answers

Fill in the blanks.

Question 1.
During solar eclipse ………….. comes between the sun and earth.
Answer:
moon

Question 2.
A solar eclipse is seen only on a ………….. day.
Answer:
new moon day

Question 3.
During lunar eclipse ……………. comes between the sun and the moon.
Answer:
earth

Question 4.
A lunar eclipse is seen only on a ………….. night.
Answer:
full moon

Question 5.
The day on which the sun reaches exactly overhead is called the …………… .
Answer:
zero shadow day

Question 6.
As seen from the earth, when a planet or star passes behind the moon, that state is called a ………….. .
Answer:
occultation

Give scientific reasons:

Question 1.
Sky appears blue to us.
Answer:

1. Sunlight is scattered by the molecules of gases like nitrogen, oxygen in the atmosphere.
2. The blue colour in the sunlight which is at shorter wavelength is scattered the most than other colours and therefore the sky appears blue.

Question 2.
Solar eclipse is either partial or total.
Answer:

1. When the moon comes in between the sun and the earth and the solar disc is corripletely covered by the moon, it is called total solar eclipse.
2. When the solar disc is not covered fully by the moon, it is partial solar eclipse.

Explain the difference:

Question 1.
Solar eclipse and Lunar eclipse.
Answer:

Solar eclipse	Lunar eclipse
1. When the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and sun cannot be seen from the part in shadow. This is called a solar eclipse.	1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon in covered this is called the lunar eclipse.
2. A solar eclipse is seen only on a new moon day.	2. A lunar eclipse is seen only on a full moon night.
3. A solar eclipse should never be watched with the naked eye. because ultra violate rays which are harmful to us reach the earth	3. A lunar eclipse can be seen with the naked eye.
4. It can be seen for a few minutes only.	4. It can be seen over a period of a few hours.

Explain diagrams:

Question 1.
Explain Solar eclipse with diagram.
Answer:
Solar eclipse:

1. During its revolution, when the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and the sun cannot be seen from the part in the shadow. This is called a solar eclipse
2. A solar eclipse is seen only on a new moon day.
3. The solar eclipse may be either partial or total,
4. Sometimes the solar disc is completely covered by the moon. This is the total solar eclipse.
5. When the solar disc is not covered fully by the moon, we have a partial solar eclipse.
6. During a solar eclipse, ultra-violet rays which are harmful to us reach the earth.
7. A solar eclipse should never be watched with the naked eye.
8. A special type of goggles should be used for this purpose.
9. Solar eclipse can be seen for a few minutes only.

Question 2.
Explain Lunar eclipse with diagram
Answer:
Lunar eclipse:

1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon is covered. This is called the lunar eclipse.
2. A lunar eclipse is seen only on a full moon night. If the whole moon comes in the shadow of the earth, it is a total lunar eclipse.
3. When the shadow of the earth is cast only on a part of the moon, it is a partial lunar eclipse. You can watch a lunar eclipse with the naked eye.
4. A lunar eclipse can be seen over a period of a few hours.

Question 3.
Write a short note on Zero Shadow Day.
Answer:

1. The day on which the sun reaches exactly overhead is called zero shadow day.
2. On this day, at noon, shadow completely disappears.
3. This event can be seen in the region between the Tropic of Cancer (23.5°N) and at tropic of Capricon (23.5°S).
4. The shadow diminishes and eventually disappears for a while only to reappear later
5. This phenomenon occurs twice every year Mumbai got to witness it on May 14, 2018 last year.

Question 4.
Explain the phenomenon of scattering of light with the help of an experiment.
Answer:

1. When the sun rises our surroundings appear illuminated. The entire sky appears bright.
2. This happens because of the dust and other tiny particles in the air. This is the scattering of sunlight by the tiny particles of the various constituents of air.
3. Had there been no atmosphere, the sky would have appeared dark during the day and of course, the sun would be directly seen.
4. This has been verified by observations from the rockets and satellites which go out of the earth’s atmosphere.

Apparatus: A table lamp with a 60 or 100 W milky bulb (LED will not do), thick black paper, sticking tape, a packing needle, 100/200 ml. glass beaker, milk or milk powder, dropper, spoon, etc.

Procedure: Cover the mouth of the lampshade properly with black paper, using sticking tape. Prick a hole of 1 to 2mm diameter in the center of the paper with the help of the packing needle.

1. Take clear water in the beaker. Light the bulb and place the beaker in contact with the hole.
2. Observe from the front and at an angle of 90°.
3. Now add 2-3 drops of milk to the water and stir. Observe again.
4. A few more drops of milk may have to be added to make the water turbid.
5. A blue tinge is seen when observed along the 90° angle. This is the scattered blue light.
6. Because the blue light is scattered, a red-yellow light is seen from the front, and the hole appears reddish.

Question 5.
Short note on Shadow.
Answer:

1. Shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
2. A shadow is formed only when a light source, an opaque object and a screen are present, e.g. during a lunar eclipse we see a part of the earth’s shadow on the surface of the moon.
3. This happens when the earth, the sun, and the moon are in a straight line with the earth between sun and the moon.
4. Here the sun acts as the light source, the earth as the opaque object and moon as the screen.
5. Shadows are formed due the rectilinear propagation of light.
6. The size and the shape of the shadow depend on the position and orientation of the opaque object between the source of light and the screen.
7. If the distance of the object from the source is decreased, then the size of the shadow increases.
8. If the object is moved away from the source, then the size of the shadow decreases.
9. In older days shadows caused by objects placed in the sun were used to measure time. Such a device is called sun dial.

Use your brain power!

Answer the following questions:

Question 1.
Eclipses and transits which will occur recently.
Answer:

• January 6, 2019 – Partial solar eclipse
• January 21, 2019 – Total Lunar eclipse
• July 2, 2019 – Total solar eclipse
• July 16, 2019 – Partial Lunar eclipse
• December 26, 2019 – Annular solar eclipse.

Find Out:

Answer the following questions:

Question 1.
If a few drops of milk are added in the experiment given the reddish colour seen from the front becomes an intense red. However, if many more drops are added the reddish colour is not seen. Why is this so?
Answer:

1. As more and more milk is added, more particles of protein and fat scatter the light and the blue colour is scattered more and more than orange and red light and the beam appears blue from the sides.
2. If few drops of milk are added, along with blue colour, orange and yellow also are scattered and only the intense red is seen from the front.
3. But when many more drops are added, even the red colour is scattered and we do not see any colour from the front.

Question 2.
What is Occultation?
Answer:
As seen from the earth, when a planet or a star passes behind the moon, that state is called an Occultation.

Complete the Chart.

Question 1.

Answer:

• A – Solar B – Lunar
• C – Total Solar
• D – Partial Solar
• E – Total Lunar
• F – Partial Lunar
• G – Moon is not in a straight line between earth and sun
• H – It is in the penumbra region of the moon
• I – The earth comes in between the sun and moon and they are not in a straight line.

7th Std Science Questions And Answers:

• Cell Structure and Micro-organisms Class 7 Questions And Answers
• The Muscular System and Digestive System in Human Beings Class 7 Questions And Answers
• Changes – Physical and Chemical Class 7 Questions And Answers
• Elements, Compounds and Mixtures Class 7 Questions And Answers
• Materials We Use Class 7 Questions And Answers
• Natural Resources Class 7 Questions And Answers
• Effects of Light Class 7 Questions And Answers
• Sound: Production of Sound Class 7 Questions And Answers
• Properties of a Magnetic Field Class 7 Questions And Answers
• In the World of Stars Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 5 Food Safety Notes, Textbook Exercise Important Questions and Answers.

Std 7 Science Chapter 5 Food Safety Question Answer Maharashtra Board

Class 7 Science Chapter 5 Food Safety Question Answer Maharashtra Board

1. Complete the following statements by using the correct option from those given below.
(Irradiation, dehydration, pasteurization, natural, chemical)

Question a.
Drying the food grains from farms under the hot sun is called …………. .
Answer:
dehydration

Question b.
Materials like milk are instantly cooled after heating up to a certain high temperature. This method of food preservation is called ……….. .
Answer:
pasteurization

Question c.
Salt is a ……….. type of food preservative.
Answer:
natural

Question d.
Vinegar is a …………. type of food preservative.
Answer:
chemical

2. Answer the following questions in your own words. 

Question a.
How is milk pasteurised?
Answer:
Boil the milk at 80°C for 15 minutes and cool it quickly. This destroys the microbes present in the milk and it can remain for a longer duration. This process is called pasteurization of milk.

Question b.
Why should we not consume adulterated food materials?
Answer:
Different types of adulterants affect our health in different ways. Some adulterants cause abdominal discomfort or poisoning while some may affect the functioning of some organs if consumed over a long period of time or even cause cancer.

Question c.
What precautions do your parents take to keep foodstuffs safe?
Answer:
Our parents take following care to keep foodstuffs safe

1. Drying of grains.
2. Boiling of milk, soups and curries from time to time.
3. Refrigeration of vegetables, fruits, milk and cooked food.
4. Candying of jams.
5. Use natural preservatives like oil, spices, neem leaves, salt, etc.
6. Use chemical preservatives in sauces, ketchups, pickles, jams and squashes.

Question d.
How does food spoilage occur? Which are the various factors spoiling the food?
Answer:
Food spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced.
Following are the factors for spoiling of food:

1. Bacteria causes food to spoil
2. Incorrect storage may spoil the food.
3. Infestation by pests.
4. Chemical reaction takes place in food and it gets spoiled.

Question e.
Which methods of food preservation would you use?
Answer:
I use following methods to preserve the food:

1. Freezing
2. Boiling
3. Salting of pickles
4. drying of grains
5. candying of jams.

3. What shall we do?

Question a.
There are vendors selling uncovered sweet-meats in open places in the market.
Answer:
We should tell them to sell the covered sweets because uncovered sweets are harmful to eat because it contains dust, dirt and germs. And buyers also should not purchase these uncovered sweets.

Question b.
A ‘pani-puriwala’ is serving the panipuri with dirty hands.
Answer:
We should tell him to wear gloves before serving panipuri because dirty hands contain dirt and germs which are harmful to us.

Question c.
We have purchased a large quantity of fruits and vegetables.
Answer:
We should keep them in refrigerator because in refrigerator, due to low temperature, fruits and vegetables do not spoil and biological and chemical reactions in fruits and vegetables are slowed down at low temperature.

Question d.
We need to protect foodstuffs from pests like rats, cockroaches, wall-lizards etc.
Answer:

1. If we do not protect foodstuffs from pests like rats, cockroaches, wall-lizards etc. then the food get spoiled by them and germs carried by them enters into the food.
2. If we eat this food then we may get food poisoning and we fall sick so we need to protect foodstuffs from pests like rat, cockroaches, wall lizards etc.

4. Find the odd-man-out. 

Question a.
Salt, vinegar, citric acid, sodium benzoate.
Answer:
Salt

Question b.
Lakhi dal, brick dust, metanyl yellow, turmeric powder.
Answer:
Turmeric powder

Question c.
Banana, apple, guava, almond.
Answer:
Almond

Question d.
Storing, freezing, settling, drying
Answer:
Storing

5. Complete the chart below.

Question a.

Answer:

Foodstuff	Adulterant
1. Turmeric powder	Metanil yellow
2. Black pepper	Dried papaya seeds
3. Rava	Iron filings
4. Honey	Sugar, water and jaggery

6. Explain why this happens and suggest possible remedies.

Question a.
Qualitative wastage of food.
Answer:
Qualitative wastage of food happens due to wrong methods of protecting food, excessive use of food preservatives, over-cooking, washing the vegetables after cutting them, mis¬handling of fruits like grapes and mangoes, miscalculation of the time required to transport food from producers to consumers are some of the reasons of qualitative wastage of food.
Possible remedies:

1. Avoid overcooking of food.
2. Store grains and other perishable foodstuffs like vegetables, fruits, milk etc. using proper methods.
3. Wash fruits and vegetables before cutting it.

Question b.
The cooked rice is underdone.
Answer:
Sometimes in a hurry if we cook the rice it is underdone.
Possible remedies: Use proper pressure cooker to cook the rice.

Question c.
The wheat that was bought is a bit moist.
Answer:
Sometimes due to sudden rain, wheat gets a bit moist. Possible remedies: Do not store the moist wheat, it gets spoiled due to fungus so first sundry it and then store in a clean and dry container to avoid microbial growth.

Question d.
The taste of yoghurt is too sour/slightly bitter.
Answer:
The taste of yoghurt is too sour/slightly bitter means it is spoiled. This happens if it is not kept in the refrigerator.
Possible remedies:- Always keep the yoghurt in refrigerator to avoid biological and chemical reactions in food materials.

Question e.
Cut fruits turned black.
Answer:
Fruit contains an enzyme called polyphenol oxidase or tyrosinase that reacts with oxygen. The oxidation reaction basically forms a sort of rust on the surface of fruits so it turns black.
Possible remedies:

1. Coat the fruits with sugar syrup
2. Add lemon juice on fruits.

7. Give reasons.

Question 1.
Food remains safe at 5° Celsius.
Answer:
Food remains safe at 5° Celsius because at 5°C, micro-organisms stop growing.

Question 2.
Nowadays, food is served in buffet style during large gatherings.
Answer:
Nowadays, food is served buffet style during large gatherings because due to buffet style quantitative wastage of food can be avoided, as people take only as much as they could eat.

Project:

Question 1.
Go to your kitchen und take notes about the food safety measures and the food wastage you see there.

Question 2.
In a science exhibition demonstrate the various methods of detecting food adulteration.

Class 7 Science Chapter 5 Food Safety Important Questions and Answers

Complete the following statements by using the correct option from those given below.
(Irradiation, dehydration, pasteurization, natural, chemical)

Question 1.
………………………. is celebrated as “World Food Day”.
Answer:
16th October

Question 2.
FSSAI means ………………………. .
Answer:
Food Safety and Standardization Authority of India

Question 3.
………………………. gas is filled in tight packets of potato wafers.
Answer:
Nitrogen

Question 4.
Common name of acetic acid is ……………………….
Answer:
Vinegar

Question 5.
………………………. is sprayed on the gunny bags containing food grains.
Answer:
Melathion

Question 6.
………………………. is used in smoking method.
Answer:
Aluminium phosphide

Question 7.
………………………. and ………………………. are emitted by radioactive isotopes in irradiation method.
Answer:
X – rays, gamma rays

Question 8.
In Maharashtra, irradiation plants have been installed at ………………………. for onions and potatoes and at for spices and condiments.
Answer:
Lasalgaon, Navi Mumbai

Question 9.
………………………. found the pasteurisation method.
Answer:
Louis Pasteur

Question 10.
………………………. adulterant is added to turmeric powder.
Answer:
Metanyl yellow

Question 11.
………………………. adulterant is added to red chilly powder.
Answer:
Brickdust

Question 12.
………………………. is used to make fruits more attractive.
Answer:
calcium carbide

Question 13.
………………………. and ………………………. harmful chemicals are mixed with cold drinks.
Answer:
carbonated soda, phosphoric acid

Question 14.
Shopkeepers change the of the ………………………. food packets fo avoid a financial loss.
Answer:
expiry date

Question 15.
Milk vendors add ………………………. to the milk to appear as higher fat content.
Answer:
urea

Question 16.
The shelf life of potatoes and onions ………………………. due to slowed-down of sprouting.
Answer:
increases

Question 17.
Serving too much food to guests at traditional feasts and banquets leads to ………………………. wastage of food.
Answer:
Quantitative

Question 18.
Miscalculation of the time required to transport food from producers to consumers leads to ……………………… . wastage of food.
Answer:
Qualitative

Question 19.
Prevention of food spoilage by microbial growth and infestation by pests is called ………………………. .
Answer:
food protection

Question 20.
………………………. is an example of a chemical preservative.
Answer:
Sodium benzoate.

Say whether True or False,, Correct and rewrite the false statement.

Question 1.
To prevent adulteration of food, it is inspected by the “Food and Drug Administration department of the government”.
Answer:
True

Question 2.
Overcooking of food increases the quality of food.
Answer:
False. Over cooking of food spoils it

Question 3.
Peanuts become rancid then, it is not good to eat.
Answer:
True

Question 4.
Oil and ghee contain fats.
Answer:
True

Question 5.
Prevention of food spoilage by microbial growth and infestation by pests is called food wastage.
Answer:
False. Prevention of food spoilage by microbial growth and infestation by pests is called food protection.

Question 6.
Serve yourself only as much as you can eat.
Answer:
True

Question 7.
Salt, sugar and oil are naturally available preservatives.
Answer:
True

Question 8.
Pickles can be preserved by salting.
Answer:
True

Question 9.
Milk vendors add urea to the milk so that it appears to have higher fat content.
Answer:
True

Question 10.
Shelf life of fruits and vegetables decreases by gamma rays emitted by radio-active isotopes.
Answer:
False. Shelf life of fruits and ‘ vegetables increases by gamma rays emitted by radioactive isotopes.

Give scientific reasons.

Question 1.
Refrigerators are used in the kitchen.
Answer:

1. Biological and chemical reactions in food materials are slowed down at low temperature.
2. As a result food remains in good condition for a longer period. Therefore refrigerators are used in the kitchen.

Question 2.
Potatoes and onions are treated with gamma rays.
Answer:
Potatoes and onions are treated with gamma rays because irradiation with gamma rays prevents their wastage due to sprouting and increases their shelf life.

Question 3.
Grains are sun-dried.
Answer:
Grains are sun-dried to preserve them because on sun drying their water content gets reduced and hence they last longer.

Question 4.
We boil milk from time to time.
Answer:
We boil milk from time to time to kill microorganisms in it and thus prevent it from getting spoilt.

Question 5.
Jams or pickles get spoilt if their jars are not sealed properly.
Answer:
If the jar is not sealed properly, micro¬organisms from the air enter in the jar and start growing on the food. Oxygen in the air helps the micro-organisms and fungi to grow faster and hence bring about the spoilage of the jams and pickles.

Question 6.
Some vendors add urea to the milk.
Answer:
Some vendors add urea to the milk so that it appears to have higher fat content.

Question 7.
Food wastage should be avoided.
Answer:
In countries like India, the food requirement is plenty and people do not get proper meals even once in a day. If food is not wasted then it could have met the need of many others. Therefore, food should not be wasted and proper measures should be implemented to stop quantitative and qualitative wastage of food.

Question 8.
Adulterated food should not be consumed.’
Answer:

1. The health of all people is endangered by food adulteration.
2. Different types of adulterants affect our health in different ways.
3. Some adulterants cause abdominal discomfort or poisoning, while some may affect the functioning of some organs if consumed over a long period of time or even cause cancer.

Can you tell?

Answer the following questions:

Question 1.
How and where food is wasted?
Answer:
Quantitative wastage of food:
1. Wrong methods of farming like hand sowing of, ts seeds, inadequate threshing, improper storage and wrong methods of distribution are some reasons for quantitative wastage of food.

2. Besides, much food is wasted as a result of the custom of offering and serving too much food to guests at traditional feasts or banquets.

3. Had it not been wasted, all this food could have met the need of many others Qualitative wastage of food: Using wrong methods of protecting food, excessive use of food preservatives, over-cooking, washing the vegetables after cutting them, mis-handling of fruits like grapes and mangoes, mis-calculation of the time required to transport food from producers to consumers, are some of the causes of quantitative wastage of food.

Question 2.
How is the food adulterated?
Answer:
Food is adulterated by the following ways:

1. Removal of some important components of food. e.g. removal of fat content of milk, essence of cloves, cardamoms, etc.
2. Mixing of a low quality inedible or cheaper material or harmful colour with food.
3. Mixing of some harmful materials like small stones, fine sand, iron filings, urea, dung of horse, sawdust etc.

How will you find out if food has been adulterated?

7th Std Science Questions And Answers:

• The Living World: Adaptations and Classification Class 7 Questions And Answers
• Plants: Structure and Function Class 7 Questions And Answers
• Properties of Natural Resources Class 7 Questions And Answers
• Nutrition in Living Organisms Class 7 Questions And Answers
• Food Safety Class 7 Questions And Answers
• Measurement of Physical Quantities Class 7 Questions And Answers
• Motion, Force and Work Class 7 Questions And Answers
• Static Electricity Class 7 Questions And Answers
• Heat Class 7 Questions And Answers
• Disaster Management Class 7 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 1 Natural Resources – Air, Water and Land Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 1 Natural Resources – Air, Water and Land Question Answer Maharashtra Board

Class 6 Science Chapter 1 Natural Resources – Air, Water and Land Question Answer Maharashtra Board

1. Fill in the blanks and rewrite the completed statements.

Question a.
The layer of ozone gas absorbs ……………. rays that come from the sun to the earth.
Answer:
Ultraviolet (U.V) rays

Question b.
Of the total water available on the earth, fresh water forms ……….. percent.
Answer:
0.3 %

Question c.
Both …………. and ………… constituents are present in the soil.
Answer:
biotic, abiotic

2. why is it said that?

Question a.
The ozone layer is a protective shell of earth.
Answer:

1. The ultra violet (UV) rays coming from the sun are very harmful for living things.
2. The ozone layer present in the lower stratosphere absorb this U.V. rays and prevent them from reaching the earth. As a result life on earth is protected.
3. Therefore, it is said that the ozone layer is a protective shell of the earth.

Question 2.
Water is life.
Answer:

1. Water is a good solvent and it dissolves many substances.
2. The human blood is made of 70% water and the sap of plant also contains a very high proportion of water.
3. All the life processes would not take place in the absence of water.
4. Hence, without water no living organism can survive.
5. Therefore, it is said that ‘water is life’.

Question c.
Sea water is useful even though it is not potable.
OR
In what way is sea water useful even though it is salty?
Answer:

1. Many fish and aquatic animals live in sea water.
2. The water from the sea evaporates to form clouds which brings rain.
3. The sea water also helps the land to cool due to breezes.
4. The salt and minerals are also obtained from sea water.
5. Corals and pearls are obtained from sea animals.
6. Thus, sea water is useful even though it is not potable.

3.  What will happen if

Question a.

Question a.
Microbes in soil get destroyed.
Answer:

1. Microbes in the soil decompose dead plants and animals and convert it into humus. This humus supplies nutrients to the soil.
2. Humus also aerates soil and holds water in it. It makes the soil more fertile.
3. If microbes are destroyed, humus will not be formed and the soil will not become fertile, making it unsuitable for growth of plants. Also dead and decaying matter will accumulate on land.

Question b.
The number of vehicles and factories in your surroundings increases.
Answer:

1. Vehicles and factories are the major cause of air pollution.
2. They release harmful gases like carbon dioxide, carbon monoxide and sulphur dioxide into the air.
3. These pollutants are harmful to the environment and to the people living in the surrounding area.
4. Hence, if the number of vehicles and factories in our surroundings increases, the air pollution will also increase.

Question c.
The total supply of potable water is finished.
Answer:

1. Water plays very important role in the survival of living organism.
2. All living things are dependent on water.
3. A very small quantity of water is potable and can be used for drinking.
4. All bodily functions are regulated by water.
5. Therefore, if total supply of potable water is finished, plants and animals will not survive and there will be no life on earth.

4. Match the following. 

Question a.

Group ‘A’	Group ‘B’
1. Carbon dioxide	a. Generation of soil
2. Oxygen	b. Rain
3. Water vapour	c. Plants and food production
4. Microbes	d. Combustion

Answer:

Group ‘A’	Group ‘B’
1. Carbon dioxide	c. Plants and food production
2. Oxygen	d. Combustion
3. Water vapour	b. Rain
4. Microbes	a. Generation of soil

5. Name the following.

Question a.
Constituents of biosphere.
Answer:
Atmosphere, hydrosphere, lithosphere and all living things on earth.

Question b.
Biotic constituents of soil.
Answer:
Microbes, worms, insects, burrowing rhodents like rats, mice, roots of trees and plants.

Question c.
Fossil fuel.
Answer:
Crude oil from which we get kerosene, petrol, diesel, paraffin wax and tar.

Question d.
Inert gases in air.
Answer:
Neon, argon, helium, krypton, xenon.

Question e.
Gases that are harmful to ozone layer.
Answer:
Chlorofluorocarbon and carbon tetrachloride.

6. True or False?

Question a.
Land and soil is the same thing.
Answer:
False – Land consists of stones, soil and big rocks.

Question b.
The water in a lake is called ground water.
Answer:
False – Water trapped below the ground over the bedrocks is called ground water.

Question c.
It takes about thousand years to form a 25 cm thick layer of soil.
Answer:
False – It almost takes around thousand years to form a 2.5 cm thick layer of soil.

Question d.
Radon is used in decorative lights.
Answer:
False – Neon is used in decorative lights.

7. Answer in your own words. 

Question a.
Explain with the help of a diagram how soil is formed.
Answer:

1. The soil on the land is formed by a natural process.
2. The abiotic components of soil are supplied through the weathering of the bedrock.
3. Due to heat, cold wind and rain the bedrock breaks down into pieces.
4. Stones, sand and soil are formed from these pieces.
5. Microbes, worms, insects, rodents and roots of trees growing on land help in weathering of rocks.
   
   This process is slow, continuous and it takes a thousand years to form 2.5 cm thick layer of mature soil.

Question b.
Why is there a shortage of water even though it occupies about 71% of the earth’s surface?
Answer:

1. 71% of earth’s surface is covered with water of, which 97% is salty water present in seas and oceans and 2.7% water is available as ground water, ice and in other forms.
2. Only 0.3% water is available as fresh water which can be used for drinking.
3. All the living organisms require water to drink. The water is used in the industry and also for farming.
4. Due to increasing population and uncontrolled usage, we experience shortage of water.

Question c.
What are the various constituents of air? Write their uses.
Answer:
Air contains gases like oxygen, carbon dioxide, nitrogen, inert gases, water vapour and dust particles. The uses of constituents of air are as follows.

Question d.
Why are air, water and land considered to be valuable natural resources?
Answer:

1. The various components of air help and support the growth of living organisms.
2. Nitrogen is used to make proteins, oxygen is used for respiration and carbon dioxide is used to make food by plants.
3. Similarly, land supports growth of terrestrial plants and animals. It provides important minerals to plants and also to human beings.?
4. It is the shelter for worms, insects and rodents and supports their growth. Plants also cannot survive without land.
5. Water is necessary for carrying out all life processes in the living organisms and without water there will be no life on earth.
6. Hence land, air and water are considered valuable natural resources.

Activity:

Natural Resources Air, Water And Land Class 6 Questions And Answers Question 1.
Obtain detailed information about the work of the India Meteorological Department.

Natural Resources Air Water And Land Class 6 Questions And Answers Question 2.
Find a remedy for water scarcity.

Class 6 Science Chapter 1 Natural Resources – Air, Water and Land Important Questions and Answers

Fill in the blanks and rewrite the completed statements.

Class 6 Science Chapter 1 Natural Resources Air, Water And Land Exercise Question 1.
……………. gas, used for refrigeration and air conditioning, destroys the ozone layer.
Answer:
Chlorofluorocarbon or carbon tetrachloride

Natural Resources Air Water And Land Class 6 Exercise Question 2.
Air becomes ……………. at higher altitudes.
Answer:
rarer

Natural Resources Air Water And Land Class 6 Question 3.
………….. of land is reduced if green trees and bushes are grown in it.
Answer:
Erosion

Natural Resources Air Water And Land Question 4.
16th September is celebrated as ………. Day all over the world.
Answer:
Ozone Protection

Natural Resources Air Water And Land Question Answer Question 5.
………….. is the layer of air that surrounds the earth.
Answer:
Atmosphere

Natural Resources Air, Water And Land Question 6.
……………. occupies the largest part of the earth’s surface.
Answer:
Hydrosphere

Natural Resources Air Water And Land Class 6 Question 7.
Gases are not found in the …………… and beyond.
Answer:
exosphere

Choose the correct alternative:

Question 1.
………….. percentage of the land is covered by water.
(a) 70%
(b) 81%
(c) 71%
(d)80%.
Answer:
71%

Question 2.
The gas used in fluorescent tubes is ………………… .
(a) Argon
(b) Helium
(c) Neon
(d) Krypton.
Answer:
Krypton

Question 3.
The ozone layer is found in the lower part of …………… .
(a) atmosphere
(b) stratosphere
(c) mesosphere
(d) trophosphere.
Answer:
stratosphere

Question 4.
Gas released in air on combustion of fuel is …………….. .
(a) Hydrogen sulphide
(b) Carbon tetrachloride
(c) Nitrogen dioxide
(d) Oxygen
Answer:
Nitrogen dioxide

Question 5.
The proportion of humus in the upper layer of good fertile soil is about ……………… .
(a) 23% to 45%
(b) 33% to 50%
(c) 30% to 53%
(d) 13% to 33%
Answer:
33% to 50%

Match the following:

Question 1.

Group ‘A’	Group’B’
1. Argon	a. temperature for obtaining low
2. Neon	b. Used in electric bulb
3. Xenon	c. Decorative lights
4. Chlorofluoro – carbon	d. Flash photography
5. Helium	e. Ozone depletion

Answer:

Group ‘A’	Group’B’
1. Argon	b. Used in electric bulb
2. Neon	c. Decorative lights
3. Xenon	d. Flash photography
4. Chlorofluoro – carbon	e. Ozone depletion
5. Helium	a. temperature for obtaining low

Name the following:

Question 1.
Substances formed when fuel burns.
Answer:
Carbon dioxide, carbon monoxide, nitrogen dioxide, sulphur dioxide and smoke.

Question 2.
Layers of the atmosphere.
Answer:
Troposphere, stratosphere, mesosphere, ionosphere and exosphere.

Question 3.
Layers of land.
Answer:
Humus, mature soil, immature soil, small rocks and stones and bedrock.

Question 4.
Gas necessary for building proteins.
Answer:
Nitrogen.

State whether True or False. Correct if False.

Question 1.
The amount of gases in the air is greatest near the surface and becomes rarer at higher altitudes.
Answer:
True.

Question 2.
Fogs, clouds, snow, and rain are produced in the exosphere.
Answer:
False – Fogs, clouds, snow and rain are formed in the troposphere and lower stratosphere of the atmosphere.

Question 3.
Fossil fuels are formed from the dead remains of animals and plants buried underground for a long period.
Answer:
True.

Explain what will happen if:

Question 1.
Forests are destroyed.
Answer:

1. Soil will get eroded due to rains as roots of trees hold the soil.
2. The land will become barren as trees helps to increase the level of ground water.
3. Amount of carbondioxide in the air will increase as trees use carbondioxide for photosynthesis and release oxygen.
4. Natural habitat of many animals will get completely destroyed.

Question 2.
What would have happened if there was no air on the earth?
Answer:

1. Air contains gases like nitrogen, oxygen, carbon dioxide, dust particles and water vapour, which are used in various piofeesses in living organisms and environment.
2. If there is no air then there will be no life as oxygen is essential for all living beings to survive. Also atmosphere is a very important filter. It prevents die harmful elements from reaching the earth.
3. Hence without air, our earth would become a cold, dark planet without any life.

Answer the following:

Question 1.
What is humus?
Answer:
Humus is the topmost layer of the soil formed d by decomposition of remains of plants and animals and it makes the soil fertile.

Question 2.
What is land made up of?
Answer:
Land is made up of stones, soil, sand and big rocks.

Question 3.
Is land flat everywhere?
Answer:
No, land is not flat everywhere. It is flat in some regions and hilly in some regions.

Question 4.
Does man produce soil/ land?
Answer:
No, man does not produce soil/land, it is produced naturally.

Question 5.
What do you see on land?
Answer:
We see mountains, rivers, valleys, ocean, also terrestrial animals and plants. We also see roads, bridges, buildings etc.

Question 6.
What has man created on land?
Answer:
Man has dug wells, borewells to lift ground water. He has also constructed bunds and dams. He has also built many industries, buildings, roads for transport.

Question 7.
If a deep pit is dug in the ground, what do you see there?
Answer:
We see different layers of land.

Answer in your own words.

Question 1.
Explain with the help of diagram various layers of land.
Answer:

• Humus – Topmost layer, fertile layer formed by decomposition of remains of plants and animals. Immature
• Soil – Sand, soil, small stones, worms and insects.
• Layer of soil and small rocks – less soil and more rocks.
• Bedrocks – main minerals are obtained from this layer, determines colour and texture of soil.

Observe the picture and answer the questions.

Question 1.
Where do you see the birds?
Answer:
The birds are flying in the sky.

Question 2.
Where is the cow grazing?
Answer:
The cow is grazing in the pasture (field).

Question 3.
Locate the trees.
Answer:
The trees are seen along the river bank.

Question 4.
Where does the river come from?
Answer:
The river flows from the mountains towards the plains.

Question 5.
Where is the aeroplane?
Answer:
The aeroplane is in the sky above the clouds.

Question 6.
Where are fishes seen?
Answer:
Fishes are seen swimming in the river water.

Question 7.
On what is the sail boat floating?
Answer:
Sail boat is floating on the water.

Observe and discuss:

Question 1.
What is the similarity in the three pictures given above?
Answer:
All the pictures given above show large scale emission of smoke through different agencies. This smoke directly mixes with the atmosphere, disturbing the balance between the constituents of air and causing air pollution.

Observe and discuss:

Observe the distribution of water on the earth surface and complete the table.

Question 1.

Answer:

Water available on earth	percentage
Seas, oceans	97%
Groundwater and water in other forms	2.7%
Water available for drinking	0.3%
Total	100%

Observe given figure carefully and answer the following.

Question 1.
For which purpose is water being used?
Answer:
Water is being used for washing clothes, for bathing, farming, drinking, and industries.

Question 2.
Do other living things use water like we do?
Answer:
Animals do not use water like us. They use water only for drinking. Some animals like buffaloes, rhinoceros, elephants use water for cooling themselves during summers.

Question 3.
What are the constituents of soil? Classify them as biotic and abiotic constituents.
Answer:
The constituents of soil are humus, soil, sand, gravel, stones, bedrock, insects, worms, microbes, roots of trees and dead leaves, burrowing rodents like mice and rats.

Biotic	Abiotic
Microbes, rodents like mice and rats, humus containing microbes and dead leaves.	Soil, sand, gravel, stones, bedrock.

Answer the following:

Question 1.
How would you save water? Give some measures you will adopt.
Answer:
Water can be saved in the following ways:

1. Repair the leaking taps and pipes and prevent wastage of water.
2. Take water in a bucket to wash a car, rather than using a hose pipe.
3. Close the tap when not required.
4. Store rainwater in underground tanks so that it can be used all round the year.
5. Water leftover after washing vegetables etc. can be used for watering plants in the garden.
6. Use water sparingly and reuse water wherever possible.

Question 2.
What measures would you take to prevent soil erosion?
Answer:

1. The trees, bushes and grass shall be planted in open spaces.
2. Shrubs will be planted along the river banks to prevent floods.
3. Proper drainage system will be provided so that there is no flooding of water.

Let’s try this

1. Take a transparent plastic bottle, a handful of soil, big stones, small stones, sand, some dry leaves and water.
2. Cut off the upper tapering part of the bottle. Put the rest of the materials in the lower part and add water.
3. Stir the mixture thoroughly and put it aside.

Observe it the next day and answer.

Question 1.
How does the mixture in the bottle look now?
Answer:
The mixture gets segregated into various layers. Heaviest substances settle down and lighter forms topmost layer.

Question 2.
Do you see the layers in it?
Answer:
Yes, we see the layers of soil.

Question 3.
What is seen in the different layers from top to bottom?
Answer:
The dry leaves are floating above the water at the top. Then the layer of the soil, which forms a layer above the sand. Below the sand we see a layer of small stones, and the big ones have settled down at the bottom of the bottle.

Question 4.
Obtain specimens of soil from various places and note the differences in the specimen with respect to colour, feel, texture and size of the particles.
Answer:

Area from where soil sample is taken	Colour	Texture
1. Own yard	Red colour	Smooth soil which is dry.
2. Garden	Black colour	Sticky soil, rich in humus and insects.
3. Hills	Red colour	Rough soil with small stones and pebbles.
4. River banks	White colour	Sandy and moist in nature.
5. Fields	Black soil	Sticky soil with fine particles, rich in humus and worms.
6. Rocky ground	Black	Coarse with stones and pebbles, hardly any fine soil is seen.

Question 5.
Observe how much water is used and for what purposes it is used in your house for a whole day. Record it in a chart. Discuss this data and find out how much water each person needs in your house.
Answer:

Purpose for which water is used	Amount of water (approx in litres)
1. Bath	50 litres
2. Brushing teeth	1 litre
3. Washing clothes and utensils	75 litres
4. Mopping the floor	10 litres
5. Drinking	8 litres
6. Cooking	6 litres
Total use of water	150 litres

Total number of persons = 3
Total water used per person = \(\frac{50}{3}\) = 50 litres.
Approximately 50 litres of water is required for 1 person.

Class 6 Questions And Answers

6th Std Science Questions And Answers:

• Natural Resources – Air, Water and Land Class 6 Questions And Answers
• The Living World  Class 6 Questions And Answers
• Diversity in Living Things and their Classification Class 6 Questions And Answers
• Disaster Management Class 6 Questions And Answers
• Substances in the Surroundings – Their States and Properties Class 6 Questions And Answers
• Substances in Daily Use Class 6 Questions And Answers
• Nutrition and Diet Class 6 Questions And Answers
• Our Skeletal System and the Skin Class 6 Questions And Answers
• Motion and Types of Motion
• Force and Types of Force Class 6 Questions And Answers

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 14 Light and the Formation of Shadows Notes, Textbook Exercise Important Questions and Answers.

Std 6 Science Chapter 14 Light and the Formation of Shadows Question Answer Maharashtra Board

Class 6 Science Chapter 14 Light and the Formation of Shadows Question Answer Maharashtra Board

1. Choose an appropriate word and fill in the blanks.

Question a.
A ……………. is a natural source of light.
Answer:
star

Question b.
A ………….. is an artificial source of light.
Answer:
candle

Question c.
When light passes through a prism, it gets separated into ………….. colours.
Answer:
seven

Question d.
The image obtained in the pinhole camera is …………. .
Answer:
inverted

Question e.
A shadow is formed when an …………… object comes in the way of light.
Answer:
opaque

Question f.
When a ………….. object comes in the way of light, light passes …………… it. options : seven, star, through, transparent, opaque, colors, shape, erect, inverted, luminous, candle.
Answer:
transparent, through

2. Write whether the following objects are luminous or non-luminous.

Question a.

Answer:

Object	Luminous /Non-luminous
A book	Non-luminous
A burning candle	Luminous
A wax cloth	Non-luminous
A pencil	Non-luminous
A pen	Non-luminous
A light bulb	Luminous
A tyre	Non-luminous
A torch	Luminous
Stars	Luminous
The planets	Non-luminous
A satellite	Non-luminous
The Moon	Non-luminous

3. Match the following.

Question a.

Natural sources of light	Man-made sources of light
The Sun	Tubelight
Stars in the night sky	Light bulb
Fireflies	Torch
Anglerfish	Burning candle
Honey mushroom	Oil lamps

Answer:

Transparent	Opaque	Translucent
Piece of glass Water	White plastic Tea kettle Note book Cloth Wooden cupboard	Tinted glass Oil paper Sheet of notebook Wax paper

4. Write the answers to the following.

Question a.
What things are necessary for the formation of a shadow?
Answer:
Things necessary for the formation of a shadow are:

1. A source of light
2. An object
3. A surface or screen on which the shadow is formed

Question b.
When can an object be seen?
Answer:
We can see an object when reflected rays reach our eyes.

Question c.
What is a shadow?
Answer:

1. If an opaque object comes in the way of a light source, light does not pass through it.
2. As a result the light does not reach a wall or any other surface on the other side of the object.
3. That part remains dark. This dark part is called the shadow of the object.

Project:

Question 1.
Prepare a Newton’s disc.

Question 2.
Find out how to save electricity with the help of the sunlight we receive during the day.

Question 3.
Read a biography of Sir C. V. Raman and find out about the discoveries he made.

Class 6 Science Chapter 14 Light and the Formation of Shadows Important Questions and Answers

Fill in the blanks.

Question 1.
The ……………. is the main natural source of light.
Answer:
Sun

Question 2.
The light emitted by an electric torch is more …………….. than that obtained from a candle.
Answer:
intense

Question 3.
The left and right sides of the original object appear to be …………….. in the mirror.
Answer:
exchanged

Question 4.
The image is as far behind the mirror as the object is in ……………… of it.
Answer:
front

Question 5.
The …………….. of the image is the same as that of the object.
Answer:
height

Question 6.
The materials through which light passes is said to be …………… .
Answer:
transparent

Question 7.
The materials through which light does not pass is said to be ………….. .
Answer:
opaque

Question 8.
The materials through which light passes partially is said to be ………….. .
Answer:
translucent

Question 9.
If an ………….. object comes in the way of a light source, light does not pass it.
Answer:
opaque, through

Question 10.
The shadow of an object formed due to sunlight is ………….. in the mornings and evenings and ……………. in the afternoon.
Answer:
long, short

Question 11.
The shadow of an object is formed only when ………….. does not pass through the object.
Answer:
light

Question 12.
Stars are ………….. .
Answer:
luminous

Question 13.
Planets, satellites are ………….. .
Answer:
non-luminous

Question 14.
The largest sundial is at ………….., New Delhi.
Answer:
Jantar Mantar

Question 15.
………….. is celebrated as National Science Day.
Answer:
28th February

Question 16.
Light travels in a straight line. This is called ………….. .
Answer:
linear propagation of light

Question 17.
The image formed on the diaphragm of the pinhole camera is ………….. .
Answer:
inverted

Question 18.
The kind of shadow an object forms depends upon the ………….. between the ………….., the object and the ………….. or the ………….. on which the shadow is formed.
Answer:
relative distance, source of light, surface, screen

State whether following statements are True or False.

Question 1.
Light travels in a straight line.
Answer:
True

Question 2.
Stars are luminous.
Answer:
True

Question 3.
Image in a pinhole camera is inverted.
Answer:
True

Question 4.
In the afternoon, shadows are long.
Answer:
False

Question 5.
Fireflies are a natural source of light.
Answer:
True

Question 6.
We see the candle clearly when we bend the tube.
Answer:
False

Question 7.
We can see our image clearly in running water.
Answer:
False

Question 8.
Tracing paper is transparent.
Answer:
False

Question 9.
The light obtained from an electric torch is more intense than that obtained from a candle.
Answer:
True

Question 10.
28tn February is celebrated as “National Science day” since 1987 in India.
Answer:
True

Question 11.
Classify the following into natural and man-made/artificial sources of light. (tubelight, light bulb, torch, burning candle, the sun, fireflies, anglerfish, honey mushroom, stars in the night sky, oil lamps, lanterns)
Answer:

Natural sources of light	Man-made sources of light
The Sun Stars in the night sky Fireflies Anglerfish Honey mushroom	Tubelight Light bulb Torch Burning candle Oil lamps Lanterns

Question 12.
Identify the transparent, opaque and translucent objects from among the following. (piece of glass, wax paper, tinted glass, oil paper, white plastic, a tea kettle, a notebook, cloth, water, a wooden cupboard, sheet of notebook.)
Answer:

Transparent	Opaque	Translucent
Piece of glass Water	White plastic Tea kettle Notebook Cloth Wooden cupboard	Tinted glass Oil-paper Sheet of notebook Wax paper

Question 13.
Classify the following into the type of images they form: Clear image, faint image, no image. (still clear water, cemented wall, wooden surface, new steel dish, flower, glossy granite cladding of a wall, mirror, butter paper).
Answer:

Clear Image	Faint Image	No Image
Still clear water, New steel dish, Glossy granite cladding of a wall, Mirror	Butter paper	Wooden surface Flower Cemented wall

Question 14.
Relate images formed with the surfaces.
Answer:

1. The clear images are formed on plane surfaces.
2. Faint or no images are formed on rough surfaces.

Answer in one sentence.

Question 1.
What are luminous objects?
Answer:
The objects which emit light i.e. which themselves are a source of light, are called luminous objects.

Question 2.
What determines the intensity of light?
Answer:
The intensity of light is determined by the extent to which the objects emit light.

Question 3.
What are non-luminous objects?
Answer:
The objects that are not sources of light themselves are called as non-luminous objects.

Question 4.
What are artificial sources of light?
Answer:
Man-made objects which emit light are artificial sources of light.

Question 5.
What are natural sources of light?
Answer:
Natural substances, materials which emit light are called natural sources of light.

Question 6.
What is linear propagation of light?
Answer:
Property of light travelling in a straight line is linear propagation of light.

Question 7.
What is reflection of light?
Answer:
The rays of light falling on an object from a source of light are thrown back from the substance of that object. This is reflection of light.

Question 8.
How do we see objects around us?
Answer:
The rays of light falling on an object from a source of light are thrown back from the surface of that object. This is called reflection of light. We see the object when the reflected rays reach our eyes.

Question 9.
What is moonlight?
Answer:
Sunlight reflected from the surface of the moon reaching us, in which we see the moon is called the moonlight.

Question 10.
What type of image is formed in the mirror?
Answer:
The image formed in the mirror is ‘laterally inverted’ i.e. right side appears as left side and left side appears as right side.

Question 11.
What change do you see in the image if you decrease or increase your distance from the mirror?
Answer:
When the distance between object and mirror is increased the size of image decreases where as, when the distance is decreased the image size increases.

Question 12.
What difference do you find in the height of the image in the mirror and yourself?
Answer:
The size of the image in the mirror is the same as that of the object.

Question 13.
What is the image on the diaphragm of the pinhole camera?
Answer:
An inverted or an upside down image of the candle is seen on the diaphragm of the pinhole camera.

Question 14.
What do you mean by transparent object?
Answer:
The objects / materials through which light passes are said to be transparent.

Question 15.
What do you mean by opaque materials?
Answer:
The materials through which light does not pass are said to be opaque.

Question 16.
What do you mean by translucent materials?
Answer:
The materials through which light passes partially are said to be translucent.

Question 17.
How is the shadow in the morning, afternoon and evening?
Answer:
The shadows are long in the mornings and evenings and short in the afternoon.

Question 18.
What is shade of a tree?
Answer:
The shade of a tree is its shadow.

Question 19.
How many colours is sunlight made up of?
Answer:
Sunlight is made up of seven colours.

Give reasons for the following.

Question 1.
When we see in the mirror, we see our image in the mirror.
Answer:
When we see our face in the mirror, the light reflected from our face falls on the mirror and gets reflected back again. Hence, we see our image in the mirror.

Question 2.
Opaque materials cast shadow.
Answer:
An opaque material does not allow light to pass. Hence, it casts a shadow.

Question 3.
Transparent and translucent object do not cast a shadow.
Answer:
Translucent objects cast a faint shadow whereas transparent objects do not cast a shadow at all because they allow light to pass through them.

Use your brain power!

Question 1.
Why is the image on the diaphragm of the pinhole camera inverted?
Answer:
1. The pinhole camera works on the principle of light travelling in a straight line.
2. The rays of light from the candle flame go in all directions.
3. We consider only two rays that pass through the hole and fall on the screen.

4. The rays intersect at the pinhole.
5. Since the rays cross over at that point, the top of the object appears at the bottom of the image and the bottom of the image appears at the top. Thus, we see an inverted image of the candle.

Question 2.
How will you light up a dark room using reflected light?
Answer:
Focusing on the wall with torch light. Mirrors or reflectors can be used to get light from outside.

Question 3.
Try to start the TV by operating the remote control from behind it.
Answer:
T.V will not start.

Question 4.
In which step is the flame of the candle seenclearly? Why?

Answer:
In step 1 the flame of the candle is seen clearly because light travels in straight line.

Can you tell?

Question 1.
Can we see anything in total darkness?
Answer:
No, we cannot see anything in total darkness.

Question 2.
What helps us to see the objects around us?
Answer:
Reflected light helps us to see objects around us.

Question 3.
What does the light in each one of the pictures originate form?
Answer:

1. Bulb
2. Firefly
3. Candle
4. Sun

Question 4.
Name the natural sources of light.
Answer:
Sun, Fireflies

Question 5.
In which objects do we see our reflection?
Answer:
All objects reflect light rays, but the best reflectors of light are mirrors, still water in a lake, new steel dish i.e. smooth shiny surfaces.

Question 6.
What difference do you notice on looking through the windows in the picture? What causes the difference? The picture shows transperant, opaque, translucent window panes. Spot them.

Answer:

1. Through the first window we can see a clear picture of things outside.
2. Second window gives a faint image.
3. Through the third window, we can’t see anything
4. The difference in the image is due to the material of the window panes.
5. The first window pane is transparent.
6. The second window pane is translucent.
7. The third window pane is opaque.

Answer the following questions in brief.

Question 1.
List factors on which shadow depends.
Answer:
Shadow depends on relative distance between the source of light, the object and the surface on which the shadow is formed.

Question 2.
How we can see that light travels in straight line.
Answer:

1. In the morning or in the afternoon, rays of light enter a slit in a door, window or a small hole in the roof.
2. As these rays of light from the slit or the hole move towards the floor, the dust particles in their way are clearly seen.
3. Due to these particles, the path of light becomes visible to us.
4. Thus we can see that their path is along straight lines.

Question 3.
What is the difference between an object and its reflection? What causes the difference?
Answer:

1. Object and its reflection result in formation of images.
2. Reflections taking place from highly polished metals, mirrors, still water etc, form clear images.
3. Reflections taking place from wooden surface, flower, book form dull, blurred images.
4. The difference in reflections is caused by the surface of the object.
5. Regular reflections have smooth, polished surfaces, hence, image is clear.
6. Diffused reflections have hard, rough surfaces, hence, image is dull.

Question 4.
List characteristics of images in a plane mirror.
Answer:

1. The left and right sides of the original object appear to be exchanged in the mirror image.
2. The image is as far behind the mirror as the object is in front of it.
3. The size of the image is the same as that of the object.

Question 8.
State the characteristics of image formed by a pinhole camera.
Answer:
Characteristics of an image formed by a pinhole camera are as follows:

1. It is inverted/upside down.
2. It can be obtained on a screen – real image.

Try this.

Question 1.
Make your friend stand in between the torch and the wall. What happens?
Answer:
Friend’s Shadow forms on the wall.

Question 2.
Place a glass filled with water on a sheet of paper in the window so it receives direct sunlight. What is seen on the paper?
Answer:
We see rainbow colours on the paper.

Question 3.
Can we do the same in a dark room with the help of a prism and a torch? What do we learn from this?
Answer:
yes, we can. Light gets seperated into seven colour. From this we learn that white light contains seven colours.

Question 4.
If you dip the wire loop in the soap water and then blow it, soap bubbles are formed. Are the beautiful colours of the rainbow seen in these bubbles?
Answer:
Yes, splitting of white light into different colours takes place.

Question 5.
What do you see on holding a CD in the sun?
Answer:
CD reflects rainbow colours, and interesting : patterns.

Question 6.
Raise your right hand. In mirror which hand of the mirror image is raised?
Answer:
Left hand of the mirror image is raised.

Question 7.
Is there any difference between your height and height of the mirror image?
Answer:
The height remains the same.

6th Std Science Questions And Answers:

• Work and Energy Class 6 Questions And Answers
• Simple Machines Class 6 Questions And Answers
• Sound Class 6 Questions And Answers
• Light and the Formation of Shadows Class 6 Questions And Answers
• Fun with Magnets Class 6 Questions And Answers
• The Universe Class 6 Questions And Answers