Class 7 – Page 5 – Maharashtra Board Solutions

Heat Class 7 Science Chapter 9 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

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:

conduction
convection
radiation.

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

Unequal heating of air above the sea and land sets up convection currents which cause sea breezes during the day time.
The land near the sea is heated by sunlight to a higher temperature than the sea.
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.
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.
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:

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.
The inner part gets hot and expands while the outer part remains cold since glass is a bad conductor of heat.
This unequal expansion causes the crack of glass bottle.
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:

Telephone wires are made up of copper metal. Metals expand on heating.
In summer the copper wire expands, thus the length of the wire increases between the two poles and instead of remaining straight it sags.
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:

During the winter, the temperature of air is low, its capacity to hold the vapour is less.
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:

Iron is a metal and metals are very good conductors of heat so it transfers heat at a much faster rate than wood.
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.
This is what makes the metal appear colder than the wood.
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:

Conduction
convection
radiation
Transfer of heat.

Answer:

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.
Convection: Transfer of heat in fluids due to formation of currents is called convection.
Radiation: Transfer of heat in all directions in the absence of a medium is called radiation.
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:

Thermoware containers keep food hot. These containers consist two boxes fitted one inside the other.
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.
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.
The container has a plastic lid. This also prevents any transfer of heat.

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

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

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.
It is shiny and can be easily seen.
It does not stick to glass.
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:

A thermos flask consists of two thin glass bottles fitted one inside the other.
The inner surfaces of the bottles have a silver coating to shine like a mirror.
A vacuum is created in the space between the two bottles by removing all the air from it.
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:

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.
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

Air is a poor conductor of heat and woollen clothes do not allow the transfer of body heat.
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:

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.
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:

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.
To allow for this expansion, gaps are kept.
If these gaps are not kept, then after expansion the rails and cement concrete would have buckled upwards due to lack of space.
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.

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.
It can measure the temperature precisely because it has large expansion coefficient.
It’s expansion is regular.
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.

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.

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.

Question a.
Label parts 1 – 4
Answer:

Vacuum
metal/plastic jar
Spring
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:

Nutrition in Living Organisms Class 7 Science Chapter 4 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

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:

Ingestion: Food is taken into the body.
Digestion: Conversion of food into simple soluble forms.
Absorption: Transfer of soluble food to the blood.
Assimilation: Utilization of absorbed food by cells and tissues for energy production, growth and repair.
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:

Insectivorous plants generally grow in soil or water deficient in nitrogen compounds.
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.
Droplets of a sticky substances found on tips of the hairs attract insects.
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:

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

Autotrophs have chlorophyll in the cell and here the organic food is prepared using sunlight, water and CO₂.
They do not depend on any other organism for survival.
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:

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.
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:

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.
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:

Rhizobium micro-organisms are useful because plants cannot take gaseous nitrogen from air.
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.

Nutrients like carbohydrates, proteins and fats are required in large quantity. These are macro-nutrients.
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.

Some organisms can produce their own food and thus nourish themselves. This is called autotrophic nutrition.
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:

Chemosynthesis is the biological conversion of one or more carbon-containing molecules and nutrients into organic matter.
It uses the oxidation of inorganic compounds or methane as a source of energy rather than sunlight.
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.

Root-nodules of leguminous plants contain the micro-organism rhizobium. These micro-organisms absorb atmospheric nitrogen and convert if into its nitrate, a compound.
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:

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.
e.g. Lichen is an example of symbiosis between algae and fungi.

Question 7.
Write about Drosera burmanii.
Answer:

It is art insectivorous plant.
The scientist Johannes Burman identified this plant in Sri Lanka in 1737. Hence, the plant is named after him.
It grows close to the ground.
Its leaves are attractively pink or red in colour with hairs at the margin.
Droplets of a sticky substance found at the tips of the hairs attract insects.
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:

Herbivores: Animals that depend on plants only for their food are called Herbivores.
Carnivores: Animals that depend on other animals for their food are called Carnivores.
Granivores: Animals that eat grains (seed) are called Granivores.
Frugivores: Animals that eat fruits are called frugivores.
Omnivores: Animals that obtain their food from both plants and animals are called omnivores.
Scavengers: Animals that obtain their food from dead bodies of animals are called Scavengers.
Decomposers: Microbes which obtain their food by decomposing the dead bodies of organisms or other materials are called decomposers.
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.
Endoparasitic nutrition: Some animals live inside the body of other animals and obtain their food. This is called endoparasitic nutrition.
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:

Amoeba does not have organs like hands and mouth.
It is a unicellular animal. It can take in food through any part of the surface of its unicellular body.
It surrounds the food particle from all sides to take it into the cell.
After that it digests the food with the help of different enzymes.
Undigested food is left behind as the amoeba moves further with the help of pseudopodia.
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:

Changes – Physical and Chemical Class 7 Science Chapter 13 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

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:

Canned food is processed food.
After certain period of time it may get spoilt due to some growth of micro-organism it may get intoxicated.
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:

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

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

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.
So a wooden article should be polished which forms a protective layer.
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:

Due to corrosion of copper or brass a greenish layer is seen to form on it.
So to protect copper and brass utensils from corrosion they are coated with tin.
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:

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

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

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

Whether a new substance is formed.
Whether it is a permanent change.
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:

Clock showing six o’clock time – It is a periodic change.
Sun was setting – A periodic change.
Breeze was blowing – A natural change.
Leaves shaking – A natural change.
Making toys from wet soil – Physical change.
Making dough from wheat flour – Physical change
Frying purees – Chemical change.
Raining – Natural change.
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:

Melting of wax
Melting of ice

Question 2.
Two chemical changes.
Answer:

Burning of wax candle
Burning of wood or paper.

Question 3.
Two periodic changes.
Answer:

Occurrence of day and night
change of seasons

Question 4.
Two non-periodic changes.
Answer:

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

Question 5.
Two reversible changes.
Answer:

Melting of wax.
Freezing water into ice.

Question 6.
Two irreversible changes.
Answer:

Ripening of a mango.
Burning of wood

Question 7.
Two natural changes.
Answer:

Lighting in the sky.
Earthquake.

Question 8.
Two manmade changes.
Answer:

Baking bread
Cooking food.

Question 9.
Two useful changes.
Answer:

Ripening of mango
Curdling of milk.

Question 10.
Two harmful changes.
Answer:

Spoiling of milk.
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:

Because when the cotton wick embedded in the candle is burnt, ash and smoke is formed.
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,

Air conditioners for getting cool air in houses offices and cars.
Wooden furniture made from wood obtained by cutting trees.
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:

An irreversible change is a permanent change that cannot be undone, cannot reverse it back to original substance.
In irreversible change new materials are always formed.
Irreversible changes are permanent changes.
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:

In permanent change
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:

Bud blooming into flower.
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:

Effects of Light Class 7 Science Chapter 17 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

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:

Space beyond the earth’s atmosphere does have some gas and cosmic dust but there is not any atmosphere.
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:

We are able to read because the sun light which falls on the book is scattered and reaches our eyes.
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:

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.
In order to protect our eyes a solar eclipse should never be watched with the naked eye.
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:

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.
The blue colour of the sky is due to the scattering of sunlight by the molecules of air.
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.
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:

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.
The higher the bird flies, the smaller the shadow it casts.
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:

The umbra, penumbra are the distinct parts of a shadow, created by any light source after striking on an opaque object.
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.
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:

Scattering of light is the deviation of light rays from its straight path.
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
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:

The sun is a star and the centre of our solar system. Everything in our solar system revolves around the sun.
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.
If the Sun didn’t rise means the Earth’s rotation had come to a screeching halt.
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.
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.
Moon will disappear, because the moon dose not produce light. We only see the moon because sunlight is reflected by the moon.
Without the sun’s warmth, Earth would quickly become a much colder place. Life would be difficult, oceans will freeze.
Without sun rays, all photosynthesis on earth would stop. All plants would die.
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:

Solar eclipse
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:

Sunlight is scattered by the molecules of gases like nitrogen, oxygen in the atmosphere.
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:

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.
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:

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
A solar eclipse is seen only on a new moon day.
The solar eclipse may be either partial or total,
Sometimes the solar disc is completely covered by the moon. This is the total solar eclipse.
When the solar disc is not covered fully by the moon, we have a partial solar eclipse.
During a solar eclipse, ultra-violet rays which are harmful to us reach the earth.
A solar eclipse should never be watched with the naked eye.
A special type of goggles should be used for this purpose.
Solar eclipse can be seen for a few minutes only.

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

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.
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.
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.
A lunar eclipse can be seen over a period of a few hours.

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

The day on which the sun reaches exactly overhead is called zero shadow day.
On this day, at noon, shadow completely disappears.
This event can be seen in the region between the Tropic of Cancer (23.5°N) and at tropic of Capricon (23.5°S).
The shadow diminishes and eventually disappears for a while only to reappear later
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:

When the sun rises our surroundings appear illuminated. The entire sky appears bright.
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.
Had there been no atmosphere, the sky would have appeared dark during the day and of course, the sun would be directly seen.
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.

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

Shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
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.
This happens when the earth, the sun, and the moon are in a straight line with the earth between sun and the moon.
Here the sun acts as the light source, the earth as the opaque object and moon as the screen.
Shadows are formed due the rectilinear propagation of light.
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.
If the distance of the object from the source is decreased, then the size of the shadow increases.
If the object is moved away from the source, then the size of the shadow decreases.
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:

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.
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.
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:

Food Safety Class 7 Science Chapter 5 Questions And Answers Maharashtra Board

January 4, 2025January 3, 2025 by Bhagya

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

Drying of grains.
Boiling of milk, soups and curries from time to time.
Refrigeration of vegetables, fruits, milk and cooked food.
Candying of jams.
Use natural preservatives like oil, spices, neem leaves, salt, etc.
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:

Bacteria causes food to spoil
Incorrect storage may spoil the food.
Infestation by pests.
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:

Freezing
Boiling
Salting of pickles
drying of grains
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:

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.
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:

Avoid overcooking of food.
Store grains and other perishable foodstuffs like vegetables, fruits, milk etc. using proper methods.
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:

Coat the fruits with sugar syrup
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:

Biological and chemical reactions in food materials are slowed down at low temperature.
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:

The health of all people is endangered by food adulteration.
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.

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:

Removal of some important components of food. e.g. removal of fat content of milk, essence of cloves, cardamoms, etc.
Mixing of a low quality inedible or cheaper material or harmful colour with food.
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:

Practice Set 31 Class 7 Answers Chapter 7 Joint Bar Graph Maharashtra Board

December 6, 2024December 5, 2024 by Prasanna

Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 31 Answers Solutions Chapter 7 Joint Bar Graph.

Joint Bar Graph Class 7 Maths Chapter 7 Practice Set 31 Solutions Maharashtra Board

Std 7 Maths Practice Set 31 Solutions Answers

Question 1.
The number of saplings planted by schools on World Tree Day is given in the table below. Draw a joint bar graph to show these figures.

School Name\Name of Sapling	Almond	Karanj	Neem	Ashok	Gulmohar
Nutan Vidyalaya	40	60	72	15	42
Bharat Vidyalaya	42	38	60	25	40

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 1

Question 2.
The table below shows the number of people who had the different juices at a juice bar on a Saturday and a Sunday. Draw a joint bar graph for this data.

Days\Fruits	Sweet Lime	Orange	Apple	Pineapple
Saturday	43	30	56	40
Sunday	59	65	78	67

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 2

Question 3.
The following numbers of votes were cast at 5 polling booths during the Gram Panchayat elections. Draw a joint bar graph for this data.

Persons\Booth No.	1	2	3	4	5
Men	200	270	560	820	850
Women	700	240	340	640	470

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 3

Question 4.
The maximum and minimum temperatures of five Indian cities are given in °C. Draw a joint bar graph for this data.

City\Temperature	Delhi	Mumbai	Kolkata	Nagpur	Kapurthala
Maximum temperature	35	32	37	41	37
Minimum temperature	26	25	26	29	26

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 4

Question 5.
The numbers of children vaccinated in one day at the government hospitals in Solapur and Pune are given in the table. Draw a joint bar graph for this data:

City\Vaccine	D.P.T. (Booster)	Polio (Booster)	Measles	Hepatitis
Solapur	65	60	65	63
Pune	89	87	88	86

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 5

Question 6.
The percentage of literate people in the states of Maharashtra and Gujarat are given below. Draw a joint bar graph for this data.

State\Year	1971	1981	1991	2001	2011
Maharashtra	46	57	65	77	83
Gujarat	40	45	61	69	79

Solution:
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 6

Maharashtra Board Class 7 Maths Chapter 7 Joint Bar Graph Practice Set 31 Intext Questions and Activities

Question 1.
Observe the graph shown below and answer the following questions. (Textbook pg. no. 51)

In which year did Ajay and Vijay both produce equal quantities of wheat?
In year 2014, who produced more wheat?
In year 2013, how much wheat did Ajay and Vijay each produce?

Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 7

Solution:

Both produced equal quantities of wheat in the year 2011.
Ajay produced more wheat in the year 2014.
Ajay’s wheat production in 2013 = 40 quintal.
Vijay’s wheat production in 2013 = 30 quintal.

Question 2.
The minimum and maximum temperature in Pune for five days is given. Read the joint bar graph and answer the questions below: (Textbook pg. no. 52)
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 8

What data is shown on X- axis?
What data is shown on Y- axis?
Which day had the highest temperature?
On which day is the minimum temperature the highest?
On Thursday, what is the difference between the minimum and maximum temperature?
On which day is the difference between the minimum and maximum temperature the greatest?

Solution:

Five days of a week are shown on X – axis.
Temperature in the city of Pune is shown on Y – axis.
Monday had the highest temperature.
The minimum temperature was highest on Wednesday.
Maximum temperature = 29.5° C
Minimum temperature = 15° C
∴ Difference in temperature = 29.5° C – 15° C = 14.5 ° C
The difference in minimum and maximum temperature is greatest on Thursday.

Question 3.
Collect various kinds of graphs from newspapers and discuss them. (Textbook pg. no. 53)
i. Histogram
Maharashtra Board Class 7 Maths Solutions Chapter 7 Joint Bar Graph Practice Set 31 9
ii. Line graph

iii. Pie chart

Solution:
(Students should attempt the above activities on their own.)

Std 7 Maths Digest

Practice Set 29 Class 7 Answers Chapter 6 Indices Maharashtra Board

December 6, 2024December 5, 2024 by Prasanna

Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 29 Answers Solutions Chapter 6 Indices.

Indices Class 7 Maths Chapter 6 Practice Set 29 Solutions Maharashtra Board

Std 7 Maths Practice Set 29 Solutions Answers

Question 1.
Simplify:
i. \(\left[\left(\frac{15}{12}\right)^{3}\right]^{4}\)
ii. (3⁴)^-2
iii. \(\left[\left(\frac{1}{7}\right)^{-3}\right]^{4}\)
iv. \(\left[\left(\frac{2}{5}\right)^{-2}\right]^{-3}\)
v. (6⁵)⁴
vi. \(\left[\left(\frac{6}{7}\right)^{5}\right]^{2}\)
vii. \(\left[\left(\frac{2}{3}\right)^{-4}\right]^{5}\)
viii. \(\left[\left(\frac{5}{8}\right)^{3}\right]^{-2}\)
ix. \(\left[\left(\frac{3}{4}\right)^{6}\right]^{7}\)
x. \(\left[\left(\frac{2}{5}\right)^{-3}\right]^{2}\)
Solution:
i. \(\left[\left(\frac{15}{12}\right)^{3}\right]^{4}\)
\(=\left(\frac{15}{12}\right)^{3 \times 4}=\left(\frac{15}{12}\right)^{12}\)

ii. (3⁴)^-2
= 3^4×(-2)
= 3^-8

iii. \(\left[\left(\frac{1}{7}\right)^{-3}\right]^{4}\)
\(=\left(\frac{1}{7}\right)^{(-3) \times 4}=\left(\frac{1}{7}\right)^{-12}\)

iv. \(\left[\left(\frac{2}{5}\right)^{-2}\right]^{-3}\)
\(=\left(\frac{2}{5}\right)^{(-2) \times(-3)}=\left(\frac{2}{5}\right)^{6}\)

v. (6⁵)⁴
= 6^5×4
= 6²⁰

vi. \(\left[\left(\frac{6}{7}\right)^{5}\right]^{2}\)
\(=\left(\frac{6}{7}\right)^{5 \times 2}=\left(\frac{6}{7}\right)^{10}\)

vii. \(\left[\left(\frac{2}{3}\right)^{-4}\right]^{5}\)
\(=\left(\frac{2}{3}\right)^{(-4) \times 5}=\left(\frac{2}{3}\right)^{-20}\)

viii. \(\left[\left(\frac{5}{8}\right)^{3}\right]^{-2}\)
\(=\left(\frac{5}{8}\right)^{3 \times(-2)}=\left(\frac{5}{8}\right)^{-6}\)

ix. \(\left[\left(\frac{3}{4}\right)^{6}\right]^{7}\)
\(=\left(\frac{3}{4}\right)^{6 \times 1}=\left(\frac{3}{4}\right)^{6}\)

x. \(\left[\left(\frac{2}{5}\right)^{-3}\right]^{2}\)
\(=\left(\frac{2}{5}\right)^{(-3) \times 2}=\left(\frac{2}{5}\right)^{-6}\)

Question 2.
Write the following numbers using positive indices:
i. \(\left(\frac{2}{7}\right)^{-2}\)
ii. \(\left(\frac{11}{3}\right)^{-5}\)
iii. \(\left(\frac{1}{6}\right)^{-3}\)
iv. \((y)^{-4}\)
Solution:
i. \(\left(\frac{7}{2}\right)^{2}\)
ii. \(\left(\frac{3}{11}\right)^{5}\)
iii. \(6^{3}\)
iv. \(\frac{1}{y^{4}}\)

Std 7 Maths Digest

Practice Set 28 Class 7 Answers Chapter 6 Indices Maharashtra Board

December 6, 2024December 5, 2024 by Prasanna

Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 28 Answers Solutions Chapter 6 Indices.

Indices Class 7 Maths Chapter 6 Practice Set 28 Solutions Maharashtra Board

Std 7 Maths Practice Set 28 Solutions Answers

Question 1.
Simplify:
i. a⁶ ÷ a⁴
ii. m⁵ ÷ m⁸
iii. p³ ÷ p¹³
iv. x¹⁰ ÷ x¹⁰
Solution:
i. a⁶ ÷ a⁴
= a^6-4
= a²

ii. m⁵ ÷ m⁸
= m^5-8
= m^-3

iii. p³ ÷ p¹³
= p^3-13
= p^-10

iv. x¹⁰ ÷ x¹⁰
= x^10-10
= x⁰= 1

Question 2.
Find the value of:
i. (-7)¹² ÷ (-7)¹²
ii. 7⁵ ÷ 7³
iii. \(\left(\frac{4}{5}\right)^{3} \div\left(\frac{4}{5}\right)^{2}\)
iv. 4⁷ ÷ 4⁵
Solution:
i. (-7)¹² ÷ (-7)¹²
= (-7)^12-12
= (-7)⁰
= 1

ii. 7⁵ ÷ 7³
= 7^5-3
= 7²
= 49

iii. \(\left(\frac{4}{5}\right)^{3} \div\left(\frac{4}{5}\right)^{2}\)
\(=\left(\frac{4}{5}\right)^{3-2}=\frac{4}{5}\)

iv. 4 ÷ 4
= 4^7-5
= 4²
= 16

Std 7 Maths Digest

Practice Set 27 Class 7 Answers Chapter 6 Indices Maharashtra Board

December 6, 2024December 5, 2024 by Prasanna

Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 27 Answers Solutions Chapter 6 Indices.

Indices Class 7 Maths Chapter 6 Practice Set 27 Solutions Maharashtra Board

Std 7 Maths Practice Set 27 Solutions Answers

Question 1.
Simplify:
i. 7⁴ × 7²
ii. (-11)⁵ × (-11)²
iii. \(\left(\frac{6}{7}\right)^{3} \times\left(\frac{6}{7}\right)^{5}\)
iv. \(\left(-\frac{3}{2}\right)^{5} \times\left(-\frac{3}{2}\right)^{3}\)
v. a¹⁶ × a⁷
vi. \(\left(\frac{\mathrm{P}}{5}\right)^{3} \times\left(\frac{\mathrm{P}}{5}\right)^{7}\)
Solution:
i. 7⁴ × 7²
= 7⁴⁺²
= 7⁶

ii. (-11)⁵ × (-11)²
= (-11)⁵⁺²
= (-11)⁷

iii. \(\left(\frac{6}{7}\right)^{3} \times\left(\frac{6}{7}\right)^{5}\)
\(=\left(\frac{6}{7}\right)^{3+5}=\left(\frac{6}{7}\right)^{8}\)

iv. \(\left(-\frac{3}{2}\right)^{5} \times\left(-\frac{3}{2}\right)^{3}\)
\(=\left(-\frac{3}{2}\right)^{5+3}=\left(-\frac{3}{2}\right)^{8}\)

v. a¹⁶ × a⁷
= a¹⁶⁺⁷
= a²³

vi. \(\left(\frac{\mathrm{P}}{5}\right)^{3} \times\left(\frac{\mathrm{P}}{5}\right)^{7}\)
\(=\left(\frac{\mathrm{P}}{5}\right)^{3+7}=\left(\frac{\mathrm{P}}{5}\right)^{10}\)

Std 7 Maths Digest

Practice Set 26 Class 7 Answers Chapter 6 Indices Maharashtra Board

December 6, 2024December 5, 2024 by Prasanna

Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 26 Answers Solutions Chapter 6 Indices.

Indices Class 7 Maths Chapter 6 Practice Set 26 Solutions Maharashtra Board

Std 7 Maths Practice Set 26 Solutions Answers

Question 1.
Complete the table below:

Sr. No.	Indices (Numbers in index form)	Base	Index	Multiplication form	Value
i.	3⁴	3	4	3 x 3 x 3 x 3	81
ii.	16³
iii.		(-8)	2
iv.				\(\frac{3}{7} \times \frac{3}{7} \times \frac{3}{7} \times \frac{3}{7}\)	\(\frac { 81 }{ 2401 }\)
v.	(-13)⁴

Solution:

Sr. No.	Indices (Numbers in index form)	Base	Index	Multiplication form	Value
i.	3⁴	3	4	3 x 3 x 3 x 3	81
ii.	16³	16	3	16 x 16 x 16	4096
iii.	(-8)²	(-8)	2	-8 x -8	64
iv.	\(\left(\frac{3}{7}\right)^{4}\)	\(\frac { 7 }{ 7 }\)	4	\(\frac{3}{7} \times \frac{3}{7} \times \frac{3}{7} \times \frac{3}{7}\)	\(\frac { 81 }{ 2401 }\)
v.	(-13)⁴	-13	4	(-13) x (-13) x (-13) x (-13)	28561

Question 2.
Find the value of.
i. 2¹⁰
ii. 5³
iii. (-7)⁴
iv. (-6)³
v. 9³
vi. 8¹
vii. \(\left(\frac{4}{5}\right)^{3}\)
viii. \(\left(-\frac{1}{2}\right)^{4}\)
Solution:
i. 2¹⁰
= 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2
= 1024

ii. 5³
= 5 × 5 × 5
= 125

iii. (-7)⁴
= (-7) × (-7) × (-7) × (-7)
= 2401

iv. (-6)³
= (-6) × (-6) × (-6)
= -216

v. 9³
= 9 × 9 × 9
= 729

vi. 8¹
= 8

vii. \(\left(\frac{4}{5}\right)^{3}\)
\(=\frac{4}{5} \times \frac{4}{5} \times \frac{4}{5}=\frac{64}{125}\)

viii. \(\left(-\frac{1}{2}\right)^{4}\)
\(=\left(-\frac{1}{2}\right) \times\left(-\frac{1}{2}\right) \times\left(-\frac{1}{2}\right) \times\left(-\frac{1}{2}\right)=\frac{1}{16}\)

Std 7 Maths Digest