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Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 5 Substances in the Surroundings – Their States and Properties Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 6 Science Solutions Chapter 5 Substances in the Surroundings – Their States and Properties

Class 6 Science Chapter 5 Substances in the Surroundings – Their States and Properties Textbook Questions and Answers

1. In the paragraph below write ‘solid’, ‘liquid’ or ‘gas’ in each of the blank (brackets) depending on the substance referred to just before.

Question a.
On a bright sunny day, Riya and Gargi are playing with a ball (…..) in the park. Gargi feels thirsty. So, Riya brings tender coconut water (…..) for her. At the same time, a strong breeze (…..) starts blowing and it also begins to rain (…..). They run back into the house (…..), change their clothes (…..) and then their mother gives them a cup (…..) of hot milk (…..) to drink.
Answer:
solid, liquid, gas, liquid, solid, solid, solid, liquid.

2. Discuss.

Question a.
Riya pours some water from her bottle into another bottle. Does it change the shape of the water?
Answer:
Yes, the shape of water changes as water is in liquid state. Liquids do not have a shape of its own. They take the shape of the container.

Question b.
Halima picks up a small stone from the ground and puts it in the water in a dish. Does the shape of the stone change?
Answer:
No, the shape of the stone does not change. Stone is a solid, hence retains its shape.

3. Write the properties of these substances.
(water, glass, chalk, iron ball, sugar, salt, flour, coal, soil, pen, ink, soap)

Question a.
Write the properties of these substances.
(water, glass, chalk, iron ball, sugar, salt, flour, coal, soil, pen, ink, soap)
Answer:
Properties of substances:

Substance	State	Properties
1. Water	Liquid	Fluidity, density, solubility, transparency, thermal conductivity.
2. Glass	Solid	Brittleness, hardness, density, transparency.
3. Chalk	Solid	Brittleness, density.
4. Iron ball	Solid	Hardness, density, malleability, ductility, electrical ductility, conductivity, thermal conductivity, luster, sonority.
5. Sugar	Solid	Brittleness, density, solubility.
6. Salt	Solid	Brittleness, density, solubility.
7. Flour	Solid	Density, solubility.
8. Coal	Solid	Brittleness, density, thermal conductivity.
9. Soil	Solid	Brittleness, density.
10. Pen	Solid	Hardness, density.
11. Ink	Liquid	Fluidity, density, solubility.
12. Soap	Solid	Brittleness, hardness, density, solubility.

4. What is sublimation? Write the names of everyday substances that sublimate.

Question a.
What is sublimation? Write the names of everyday substances that sublimate.
Answer:

1. The change of a solid substance directly into a gas or vapour without first changing into liquid is called sublimation.
2. Substances that sublimate: Camphor, napthalene balls, ammonium chloride, iodine.

5. What is made from? Why? 
a. A sickle to cut sugarcane.
b. The sheets used for roofing.
c. A screwdriver
d. A pair of tongs.
e. Electric cables.
f. Ornaments.
g. Pots and pans.

Question a.
A sickle to cut sugarcane.
Answer:
A sickle is made of iron. An iron sickle is hard and malleable. When sharpened it will be able to cut the hard sugarcane.

Question b.
The sheets used for roofing:
Answer:

1. The sheets used for roofing are made of plastic, aluminium.
2. Plastic is hard, hence, protects against weather conditions.
3. Plastic is transparent, hence, sunlight can pass through it.
4. Aluminium is hard, light weight and durable, hence, protects against all weather conditions.
5. Malleable hence formed into thin sheets.

Question c.
A screwdriver:
Answer:

1. A screwdriver is made up of iron, steel, aluminium.
2. A screwdriver possesses property of hardness hence, it easily pierces a screw in piece of wood, wall, metals etc.

Question d.
A pair of tongs:
Answer:

1. A pair of tongs are made up of iron, steel aluminium etc. Tongs are used to lift hot, boiling utensils or vessels.
2. Tongs are hard, ductile and malleable.
3. Hence, have strong grip to hold utensils.
4. Rubbers fitted on the ends will protect from thermal conduction, from bums.

Question e.
Electric cables:
Answer:

1. Electric cables are metal wires (thin) wound in plastic.
2. Metal wires possess the property of hardness, ductility, electrical conductivity.
3. Plastic /rubber covering possesses the property of hardness, elasticity and are bad conductors of heat and electricity.

Question f.
Ornaments:
Answer:

1. They are made up of metals like gold and silver.
2. They possess the property of hardness, ductility, malleability, lustre.

Question g.
Pots and pans: Answer:

1. They are used to cook food, hence metals like aluminium, steel are used.
2. They possess the property of hardness, ductility, malleability, thermal conductivity, electrical conductivity, (microwave ovens)

6. What will happen if ….? And why?

Question a.
Nails are made of plastic
Answer:
If nails are made of plastic, they will not be able to pierce through other substances on being pushed or forced by a hammer. Plastic lacks the property of hardness.

Question b.
A bell is made of wood.
Answer:

1. If a bell is made of wood it will never make a ringing sound. A wooden bell does not have the property of being sonorous.
2. Sonority is the property of metals to produce a ringing sound.

Question c.
Rubber is not fitted on a pair of tongs.
Answer:

1. Rubber is a bad conductor of heat and electricity. It will not allow heat to pass to the hands/handle of the tongs, thus protecting us.
2. Pair of tongs are made up of metals which conduct heat and electricity. They have file property of thermal conduction and electrical conduction.
3. If rubber is not fitted on a pair of tongs, we will not be able to lift hot objects with it.

Question d.
A knife is made of wood.
Answer:
Wood does not have the property of malleability. Therefore, the edge of wooden knife will be blunt. Hence, we will not be able to cut anything with it.

Question e.
An axe is made of rubber.
Answer:

1. If an axe is made of rubber, it will not be used to cut wood or tree.
2. Rubber does not have the property of hardness that is required to push through to cut it.

7. Who am I?

Question a.
I’m found in a thermometer, I measure your temperature.
Answer:
Mercury

Question b.
I make things hot or cold.
Answer:
Heat

Question c.
I have no shape whatsoever!
Answer:
Liquid, gases

Question d.
I dissolve in water, but not in kerosene.
Answer:
Salt

8. Why does this happen? 

Question a.
Coconut oil thickens in winter.
Answer:
Coconut oil is in liquid state. In winter the surrounding temperature / atmospheric temperature starts decreasing. Coconut oil starts cooling or losing heat, it changes to solid state.
Thus coconut oil thickens in winter.

Question b.
Kerosene left open in a dish disappears.
Answer:
When kerosene is left open in a dish, it is exposed to surrounding temperature. As the temperature is more, kerosene starts continuously evaporating and finally disappears.

Question c.
The fragrance of incense sticks lighted in one corner of a room spreads to the other corner.
Answer:
The fragrance of incense sticks is given out in the form of scented vapours. As vapours are in gaseous state, the gas molecules spread out in the room. The molecules of gas move very fast and there are no forces to stop them from going apart. Therefore the fragrance of incense sticks lighted in one corner of room spreads to the other corner.

Question d.
What you see in the picture.

Answer:
The mass of plastic ball is less than an apple. This difference is because of their densities. Since an apple has greater density, it will sink to the bottom on other hand the plastic ball has lesser density, it will float over water surface.

Activity: 

Question 1.
Find out how the big statues of wax are made.

Question 2.
Visit a jeweller’s shop and find out how ornaments are made.

Class 6 Science Chapter 5 Substances in the Surroundings – Their States and Properties Important Questions and Answers

Fill in the blanks:

Question 1.
The state of a substance changes if it is …………… or …………… .
Answer:
heated, cooled

Question 2.
Every substance in our surroundings is found in either the ……………, …………… or gaseous state.
Answer:
solid, liquid

Question 3.
On …………… heat, the substance changes from solid to liquid and liquid to gas.
Answer:
gaining

Question 4.
When the substance cools, or …………… heat, it changes from gaseous to liquid and liquid to solid state.
Answer:
loses

Question 5.
A …………… amount of heat must be gained or lost before the state of a substance can change.
Answer:
specific

Question 6.
When a substance gets heat, it becomes …………… and then …………… .
Answer:
warm, hot

Question 7.
If the substance is very hot, we could get …………… .
Answer:
scalded

Question 8.
A thermometer is used to measure …………… .
Answer:
temperature

Question 9.
…………… is the unit of measuring temperature.
Answer:
Degree Celsius (°C)

Question 10.
Nowadays, …………… thermometers are frequently used.
Answer:
digital

Question 11.
Solids have a shape of its …………… .
Answer:
own

Question 12.
Solids have a …………… volume.
Answer:
definite

Question 13.
Liquids take the shape of the …………… .
Answer:
container

Question 14.
Liquids have a …………… volume.
Answer:
specific

Question 15.
Air occupies all the available …………… .
Answer:
space

Question 16.
Evaporation occurs from the …………… of the water.
Answer:
surface

Question 17.
At sea-level, pure water boils at …………… .
Answer:
100°C

Question 18.
Condensation of steam takes place at …………… .
Answer:
100°C

Question 19.
The temperature of a substance can fall below …………… .
Answer:
0°C

Question 20.
Ice melts at …………… .
Answer:
0°C

Question 21.
Each substance has a specific boiling point which is also its …………… point.
Answer:
condensation

Question 22.
Each substance has a specific melting point which is the same as its …………… point.
Answer:
freezing

Question 23.
Candles are made by melting …………… wax.
Answer:
paraffin

Question 24.
Solid carbon-dioxide is …………… .
Answer:
dry ice

Question 25.
Liquid …………… is used in animal husbandry.
Answer:
nitrogen

Question 26.
Sand is melted to make …………… .
Answer:
glass

Question 27.
Iron is melted to make …………… .
Answer:
tools

Question 28.
Substances can be identified by studying their …………… .
Answer:
properties

Question 29.
Substances that break into small particles are said to be …………… .
Answer:
brittle

Question 30.
The …………… of any liquid is determined by how easily it flows.
Answer:
fluidity

Question 31.
Between substances of the same volume, the ones with greater density are …………… than those of lesser density.
Answer:
heavier

Question 32.
The property of a substance of getting …………… is called its solubility.
Answer:
dissolved

Question 33.
Minerals from the earth’s crust are …………… to obtain metals.
Answer:
processed

Question 34.
Metals can be converted into …………… by hammering.
Answer:
sheets

Question 35.
Metals can be stretched and drawn into …………… .
Answer:
wires

Question 36.
All metals are …………… of electricity to a greater or lesser extent.
Answer:
conductors

Question 37.
Every metal has a …………… colour by which it can be identified.
Answer:
specific

Question 38.
Metals produce …………… sound.
Answer:
ringing

Question 39.
Metals form a …………… group of substances.
Answer:
separate

Question 40.
Heat is the cause of the change of the state of …………… .
Answer:
substances

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Boiling water	a. > 35° C
2. Body temperature	b. 0° C
3. Freezing water	c. < 5° C
4. Air (summer afternoon)	d. < 15° C
5. Inside a fridge	e. < -18° C
6. Air (winter night)	f. 100° C
7. Inside the freezer	g. 37°C

Answer:

Column ‘A’	Column ‘B’
1. Boiling water	f. 100° C
2. Body temperature	g. 37°C
3. Freezing water	b. 0° C
4. Air (summer afternoon)	a. > 35° C
5. Inside a fridge	c. < 5° C
6. Air (winter night)	d. < 15° C
7. Inside the freezer	e. < -18° C

Answer in one sentence:

Question 1.
What is change of state of substances?
Answer:
When a substance changes from one state to another, the process is called change of state of the substance.

Question 2.
When does state of substance change?
Answer:
State of substance changes when it is heated or cooled.

Question 3.
In which state do substances exist in our surroundings?
Answer:
The substances exist in solid, liquid and gaseous form in our surroundings.

Question 4.
What happens when a substance gains heat?
Answer:
When a substance gains heat, it changes its state i.e. from solid to liquid and liquid to gas.

Question 5.
What happens when a substance loses heat?
Answer:
When a substance loses heat, it changes its state from gaseous to liquid and liquid to solid state.

Question 6.
How do we tell how hot or cold a substance is?
Answer:
The temperature on the thermometer will tell us how hot or cold a substance is.

Question 7.
What is the unit of measuring temperature.
Answer:
Degrees Celsius (°C) is the unit of measuring temperature.

Question 8.
What is the boiling point of water?
Answer:
The boiling point of water is 100° C.

Question 9.
What is condensation?
Answer:
When vapour cools, it is converted into liquid again. This process is condensation.

Question 10.
At what temperature condensation of steam takes place?
Answer:
Condensation of steam takes place at 100° C.

Question 11.
What is the freezing point of water?
Answer:
0° C is the freezing point of water.

Question 12.
What is the temperature of air in the freezer of a refrigerator?
Answer:
-18° C is the temperature of air in the freezer of a refrigerator.

Question 13.
At what temperature ice melts?
Answer:
Ice melts at 0° C.

Question 14.
How are candles made?
Answer:
Candles are made by melting paraffin wax.

Question 15.
What is the use of solid carbon-dioxide?
Answer:
Solid carbon-dioxide (dry ice) is used to make ice cream and to keep it frozen.

Question 16.
What is the use of liquid nitrogen?
Answer:
Liquid nitrogen is used in animal husbandry.

Question 17.
What is sublimation?
Answer:
The change of a solid substance directly into gas or vapour without changing into a liquid is called sublimation.

Question 18.
Define brittleness / What is brittleness?
Answer:
Some substances break into small pieces or particles. Such substances are said to be brittle. This property of substances is called brittleness.

Question 19.
Define hardness / What is hardness?
Answer:
The hardness of a substance is determined by how much resistance it offers to the substances being pushed through it.

Question 20.
Define elasticity / What is elasticity?
Answer:
Some substances change their shape when a force is applied on them but return to their original shape and size when the force is removed. This property is called elasticity.

Question 21.
Define fluidity / What is fluidity?
Answer:
Liquids flow downward on a sloping surface. This property is called fluidity.

Question 22.
How is fluidity of any liquid determined?
Answer:
Fluidity of any liquid is determined by how easily it flows.

Question 23.
Define density / What is density?
Answer:
The mass of different substances having the same volume can be different. This difference is because of the difference in their densities. Between substances of the same volume, the ones with greater density are heavier than those of lesser density.

Question 24.
Define solubility / What is solubility?
Answer:
The property of a substance of getting dissolved is called its solubility.

Question 25.
Define transparency / What is transparency?
Answer:
When we can look through a substance and see things on the other side, then that substance is said to be transparent. This property of the substances is called transparency.

Question 26.
List some transparent substances.
Answer:
Glass, air, clean water and some types of plastic are transparent substances.

Question 27.
What are metals?
Answer:
Metals are substances like copper, gold, iron, aluminium. They are found in the form of minerals deep inside the earth. Minerals from the earth’s crust are processed to obtain metals.

Question 28.
Define malleability. / What is malleability?
Answer:
Metals can be converted into sheets by hammering. This property of metals is called malleability.

Question 29.
Define ductility. / What is ductility?
Answer:
Metals can be stretched and drawn into thin wires. This property of metals is called ductility

Question 30.
Name some ductile metals.
Answer:
Metals like silver, gold, platinum can be drawn into fine wires.

Question 31.
Define electrical conductivity. / What is electrical conduction?
Answer:
Electricity flows through metals. All metals are conductors of electricity to a greater or lesser extent.

Question 32.
Define thermal conductivity. / What is thermal conductivity?
Answer:
Metals allow heat to flow through them. This property is called thermal conductivity

Question 33.
What is lustre?
Answer:
The typical shine or characteristic colour by which metal can be identified is called lustre.

Question 34.
What is sonority of metals? / Define sonority.
Answer;
Metals produce a ringing sound. This property is called the sonority of metals.

Give scientific reasons for following:

Question 1.
Metals are used to make musical instruments.
Answer:
Metals possess the property of being sonorous, i.e. produce a ringing sound. Hence, they are used to make musical instruments.

Question 2.
Ornaments are made up of metals.
Answer:
Metals have the property of being malleable, ductile, lustrous. Hence, ornaments are made up of metals.

Question 3.
Why should we not put our hand or finger in the water to judge the hotness of water?
Answer:
We should never put our hand or finger in the water to judge how hot it is because that is not an accurate measure. Besides if the substance is very hot, we could get scalded.

Can you tell?

Question 1.
Why are electric boards fitted on the wall made of plastic or wood?
Answer:
Plastic or wood are bad conductors of heat and electricity. Electric boards are made up of plastic or wood. So that while touching we will not get electric shock.

Question 2.
The handle of cooker is made of plastic. Why?
Answer:
Cooker is made of metal. When food is cooked in it, it gets heated and the whole of its body becomes hot due to thermal conductivity. Hence with the plastic handle we can easily lift the hot cooker as plastic is a bad conductor of heat.

Question 3.
Use your brain power!
On opening a box of camphor, its smell spreads all around. Why does this happen?
Answer:

1. Camphor is a sublimate substance.
2. When a box of camphor is opened it changes its state from solid to gas or vapour state.
3. This change takes due to the process of sublimation where camphor absorbs heat from surrounding to change from solid to gaseous state.
4. Camphor particles in gaseous state start spreading all around.
5. Hence on opening a box of camphor its smell spreads all around.

Question 4.
Identify the objects shown in fig. 5.14. From which substances are they made? What are these substances called as a group?
Answer:
In fig 5.14, the metallic bars are shown, these bars are made up of shiny solid. These substances are called metals.

Question 5.
Name the solid, liquid and gaseous states of water.
Answer:

• Solid- Ice
• Liquid – water
• Gas – water vapour.

Question 6.
Read this list of substances:
spirit, camphor, petrol, ghee, coconut oil, naphthalene balls, ammonium chloride (navsagar).

Question a.
Which one freezes in winter?
Answer:
Coconut oil, ghee.

Question b.
Which liquids have you seen change into a vapour?
Answer:
Spirit, petrol.

Question c.
Which solid directly changes into gaseous state?
Answer:
Camphor, naphthalene balls, ammonium chloride.

Question 7.
The chart given below shows the boiling point and freezing point of some substances. State whether these substances are solid, liquid or gaseous at room temperature.

Substance	Freezing Point	Boiling Point
Candle	60 °C	350 °C
Plastic	> 250 °C	954 °C
Iron	1535 °C	2862 °C

Answer:
Candle, plastic and iron are in solid state at room temperature.

Distinguish between solids, liquids and gases.
Answer:

Solids	Liquid                                                  Gases
e.g.: A piece of iron	e.g.: Water, spirit, oil	e.g.: Air
Has a shape of its own, Retains shape, no matter how it is kept.	Does not have a shape of its own. Takes the shape of the container.	Does not have a shape of its own. Occupies all the available space.
Has a definite volume. Solids like sugar, sand when poured on a flat surface, form a heap.	It has a specific volume. Occupies definite portion of a container. Spreads on a flat surface on pouring. Flows downwards along a slope. Takes the shape of the surface.	Does not have a definite volume. On changing the pressure on a gas in a closed container, its volume also changes.

Distinguish between Boiling and Melting.
Answer:

Boiling	Melting
1. When heat is supplied to liquids, they boil.	1. When heat is supplied to solids, they melt.
2. Boiling leads liquids to vapour/gaseous state.	2. Melting leads solids to liquid state.
3. The temparature at which liquid starts boiling continuously is called boiling point.	3. The temperature at which solid turns to liquid completely is called melting point.

Answer the following briefly:

Question 1.
List properties of solids
Answer:

1. Solids have its own shape i.e. Retains shape, no matter how it is kept.
2. Solids have definite volume.
3. e.g. Sand when poured on a flat surface form a heap.

Question 2.
List properties of liquids.
Answer:

1. Liquid does not have a shape of its own. Takes the shape of the container.
2. A liquid has a specific volume i.e. occupies definite portion of a container.
3. Liquids: e.g. water, milk, kerosene.

Question 3.
List properties of gases.
Answer:

1. Gases does not have a shape of its own.
2. Occupies all the available space.
3. Does not have a definite volume.
4. e.g. Air.

Question 4.
Explain with example how liquids take the shape of the surface.
Answer:
Liquids have a specific volume. They occupy definite portion of a container. Liquids spreads on a flat surface on pouring. Liquids flow downwards along a slope.

Question 5.
Explain Ebullition.
Answer:

1. As the water gets heated, its temperature increases and it evaporates at a faster and faster rate.
2. When water kept on a stove attains a particular temperature or level of heat, then evaporation takes place in all parts of the body of water.
3. Then we see water bubbles rising at a faster and faster rate to the surface and steam mixing in the air.
4. This is called boiling of water or Ebullition.

Question 6.
Explain: Boiling point and condensation point of water are one and the same.
Answer:
Water boils at 100°C. i.e. boiling point of water is 100°C. Condensation of steam also takes place at 100° C. Thus boiling point and condensation point of water are one and the same.

Question 7.
Explain freezing point of water.
Answer:

1. Water kept in a fridge or on ice becomes cooler and cooler i.e. its temperature falls.
2. At a certain temperature water does not cool further but starts freezing and forms ice.
3. The temperature at which this happens is called the freezing point of water. (0° C)

Question 8.
Explain: Freezing point and melting point of water are same.
Answer:

1. The temperature at which water does not get any cooler but starts freezing and forming ice is 0° C.
2. When ice gets heat, it starts melting or changes into liquid state at 0° C.
3. Thus, freezing point and melting point of water are one and the same.

Question 9.
List various uses of changes in physical state.
Answer:

1. Candles are made by melting paraffin wax.
2. Solid carbon-dioxide (dry ice) is used to make ice-cream and to keep it frozen.
3. Liquid nitrogen is used in animal husbandry.
4. Sand (silica) is melted to make glass.
5. Metals like gold and silver are melted to make ornaments.
6. Iron is melted to make tools.

Question 10.
List the properties of substances:
Answer:
The properties of substances are

1. Brittleness
2. Hardness
3. Elasticity
4. Fluidity
5. Density
6. Solubility
7. Transparency

Question 11.
List properties of metals:
Answer:
The properties of metals are

1. Malleability
2. Ductility
3. Electrical conductivity
4. Thermal conductivity
5. Lustre
6. Sonority

Question 12.
How can we change the volume of a gas?
Answer:
On changing the pressure on a gas in a closed container we can change its volume.

Can you tell?

Question 1.
Does water change into vapour the moment we place the vessel on a stove? Does water kept in fridge change at once into ice?
Answer:
No, it doesn’t. Water slowly changes from one state to another.

Question 2.
How do we tell how hot or cold a substance is?
Answer:
A thermometer is used to measure the temperature of the subatance which tell us hot or cold it is.

Question 3.
How will you identify the following

Question i.
A glass: Is it made of plastic, steel or glass?
Answer:
Glass is made of glass as it is transparent.

Question ii.
A rod: Iron or aluminium.
Answer:
A rod is made of iron as it is heavy.

Question iii.
A door: Wooden or glass?
Answer:
A door is wooden as it is opaque.

Question iv.
A white powder: Salt or chalk powder?
Answer:
If powder dissloves in water it is salt and if it does not dissolves in water it is chalk.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 19 Properties of a Magnetic Field Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 19 Properties of a Magnetic Field

Class 7 Science Chapter 19 Properties of a Magnetic Field Textbook Questions and Answers

1. Write the appropriate terms in the blanks:

Question a.
The alloys called …………. and …………. are used for making industrial magnets.
Answer:
alnico, Nipermag

Question b.
A magnetic field can pass through ………… and …………. .
Answer:
cardboard, bottle

Question c.
The intensity of a magnetic field is indicated by the lines of …………. .
Answer:
force

Question d.
The real test of a magnet is ……………… .
Answer:
repulsion

2. With whom should I pair up?

Question a.

Column ‘A’	Column ‘B’
1. Compass	a. The highest magnetic force
2. Door of a cupboard	b. Like poles
3. Repulsion	c. A magnet
4. Magnetic pole	d. A magnetic needle

Answer:

Column ‘A’	Column ‘B’
1. Compass	d. A magnetic needle
2. Door of a cupboard	c. A magnet
3. Repulsion	b. Like poles
4. Magnetic pole	a. The highest magnetic force

3. Write answers to the following questions:

Question a.
Distinguish between the two methods of making artificial magnets
Answer:

Single touch method	Double touch method
1. In this method, one magnet is used to magnetise the steel bar.	1. In this method, two magnets are used to magnetise the steel bar.
2. In this method, the magnet is dragged from one end of the steel bar to another end.	2. In this method, two magnets are dragged from the middle of the steel bar to the opposite directions.
3. As only one magnet is used to induce magnetism, this method is called single touch method.	3. As two bar magnets are used to induce magnetism, this method is called double-touch method.
4. The magnetism created by this method is of low strength and lasts for a short time.	4. The magnetism created by this method is of high strength and lasts for a longer time.

Question b.
Which substances are used for making electromagnets?
Answer:
The substances used for making electromagnets are, an iron nail, insulated copper wire, one or more batteries and a pair of wire strippers.

Question c.
Write a note on magnetic field
Answer:

1. The region around a magnet where the magnetic force acts on an object is called a magnetic field.
2. The magnetic field around a magnet can be shown by means of magnetic lines of force.
3. The intensity of the magnetic field can be obtained from the number of lines of force.
4. The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
5. A magnetic field is the magnetic effect of electric currents and magnetic materials.
6. The magnetic field at any given point is specified by both the direction and the magnitude.
7. Magnetic fields are produced by electric current.

Question d.
Why is a magnetic needle used in a compass?
Answer:

1. The magnetic compass is the most familiar compass type.
2. It functions as a pointer to magnetic ‘north’ the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the earth’s magnetic field.
3. A compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal direction.

Question e.
Explain with the help of a diagram how the intensity and direction of the magnetic field of a bar magnet can be determined.
Answer:

1. The region around a magnet where the magnetic force acts on an object is called a magnetic field.
2. The magnetic field around a magnet can be shown by means of magnetic lines of force.
3. The intensity of the magnetic field can be obtained from the number of lines of force.
4. The intensity of a magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
5. A magnetic field is the magnetic effect of electric currents and magnetic materials.
6. The magnetic field at any given point is specified by both the direction and the magnitude.
7. Magnetic fields are produced by electric current.

4. Give detailed information about how the merchants of olden times used a magnet while travelling.

Question a.
Give detailed information about how the merchants of olden times used a magnet while travelling.
Answer:

1. The merchants of older times used a magnet whose north-south side was known.
2. When the magnet is freely suspended, the north pole of the magnet settles in the direction of the geographic north pole of the earth.
3. This is how the merchants come to know the directions while travelling.
4. The idea for using loadstone in a compass first appeared in China.
5. The first compass were made of loadstone, a naturally magnetised ore of iron.
6. The Chinese used “south pointing spoon” which when thrown upon the ground comes to rest pointing at the south.
7. Then the transition was made from loadstone spoons to iron needles.
8. In the medieval period a magnetic needle in the shape of a fish, floating in the bowl of water was used as a compass, pointing south.
9. It was called floating compass.
10. In the twentieth century, liquid filled magnetic compass began to appear.
11. There is a lesser known compass called dry mariners compass.

Project:

Question a.
Obtain information about the function of metal detectors.

Class 7 Science Chapter 19 Properties of a Magnetic Field Important Questions and Answers

Write the appropriate terms in the blanks:

Question 1.
The magnetic lines of force always run from the north pole to the ……………. .
Answer:
south pole

Question 2.
The unit of magnetic field strength is …………….. .
Answer:
A/M (Amperes per metre)

Question 3.
The earth behaves like a giant ………… .
Answer:
barmagnet

Question 4.
The ……………. properties of magnetic field was proposed by scientist
Answer:
Michael Faraday

Question 5.
The region around a magnet where the magnetic force acts on an object is called the …………. .
Answer:
magnetic field

Question 6.
The ……………. of the magnetic field can be obtained from the number of lines of force.
Answer:
strength

Question 7.
The function of the metal detector is based on ………… .
Answer:
electromagnets

Question 8.
The magnetism is ………….. in the case of an electromagnet.
Answer:
temporary

Match the following:

Question 1.

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	a. Electromagnet
2. Doorbell magnet	b. Permanent magnet
3. Nickel, cobalt, aluminium	c. Iron, nickel, titanium, aluminium
4. Cupboard magnet	d. Magnetic metals
5. Lodestone	e. Mariner’s compass
6. Nipermag	f. Alnico

Answer:

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	d. Magnetic metals
2. Doorbell magnet	a. Electromagnet
3. Nickel, cobalt, aluminium	f. Alnico
4. Cupboard magnet	b. Permanent magnet
5. Lodestone	e. Mariner’s compass
6. Nipermag	c. Iron, nickel, titanium, aluminium

Write True or False correct and rewrite the false statements:

Question 1.
Material alnico is a mixture of aluminium, nickel and iron.
Answer:
False. Alnico is an alloy of aluminium, nickel and cobalt

Question 2.
Nipermag is alloy of iron, nickel, cobalt.
Answer:
False. Nipermag is an alloy of iron, nickel, aluminium and titanium

Question 3.
The magnetic force is concentrated at the centre of the magnet.
Answer:
False. The magnetic force is concentrated at the poles of the magnet.

Question 4.
Magnetism of electromagnet is permanent.
Answer:
False. Magnetism of electromagnet is temporary

Question 5.
Like poles attract each other and unlike poles repel each other.
Answer:
False. Like poles repel each other and unlike poles attract each other

Question 6.
Two poles of a magnet cannot be separated from each other.
Answer:
True.

Answer in one or two sentences:

Question 1.
In which direction does a freely suspended magnet settle?
Answer:
The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth. It settles in north-south direction.

Question 2.
Write any two functions of metal detectors.
Answer:

1. Metal detectors are used in very important places like an airport, bus station, certain temples and buildings to inspect those who are entering these places.
2. To detect very precious articles.

Question 3.
Which magnetic poles attract each other?
Answer:
Opposite magnetic poles attract each other.

Question 4.
What metals are used for making magnets?
Answer:

1. Magnets are made from alloys of iron, cobalt and nickel.
2. Nipermag is an alloy made up of iron, nickel, aluminium and titanium whereas alnico is an alloy made up of aluminium, nickel and cobalt.

Give scientific reasons:

Question 1.
Earth is called as a gigantic magnet.
Answer:

1. The earth is called as a gigantic magnet because north pole of a freely suspended magnet always settles in the direction of the geographic north pole of the earth.
2. It means that the South pole of some gigantic magnet must be near the geographic north pole of that magnet, near the geographic south pole of the earth.
3. Gilbert inferred from this that the earth itself is a gigantic magnet.

Question 2.
A bar magnet kept on the cardboard arranges the iron fillings in line.
Answer:

1. A bar magnet kept on the cardboard arranges the iron fillings in line because of the ‘magnetic lines of force’.
2. These magnetic lines gauge the intensity of the bar magnet.
3. The intensity of the magnetic field is low where the lines of force are sparse and the intensity is high where the lines of force are concentrated.
4. Therefore, the iron fillings arrange themselves according to intensity of the magnetic lines of force.

Write short note on:

Question 1.
Functions of metal detector.
Answer:

1. A metal detector is an electronic instrument which detects the presence of metals nearby.
2. The function of these machines is based on electromagnets.
3. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground.
4. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects.
5. Metal detectors in the food manufacturing industry are used to detect and eliminate threats of metal contaminants in food.
6. Metal detectors are used in very important places like an airport, bus station, temples, hospitals, railway stations, theaters, malls.
7. They are used for inspection of persons entering these places.
8. In geology, these machines are used to detect the presence and quantity of metals.

Question 2.
Write down the characteristics of magnets.
Answer:

1. A freely suspended magnet settles in the north- south direction always.
2. Magnets attract objects of iron, cobalt and nickel.
3. The force of attraction of a magnet is greater at its poles than in the middle.
4. Like poles of two magnets repel each other.
5. Opposite poles of two magnets attract each other.
6. If a bar magnet is suspended by a thread and if it is free to rotate its south pole will move towards the north pole of the earth.

Question 3.
Characteristic of magnetic lines of force
Answer:

1. Magnetic lines of force start from the north pole and end at the south pole.
2. They are continuous through the body of magnet. These are imaginary lines.
3. Magnetic lines of force can pass through iron more easily than air
4. The number of magnetic lines force determines the strength of the magnetic field at a particular point.
5. Two magnetic lines of force do not intersect each other.
6. They contract longitudinally and expand laterally.

Can you tell?

Answer the following questions:

Question 1.
Why does freely suspended magnet always settle in the north-south direction?
Answer:

1. Gilbert gave a scientific explanation that earth itself is a gigantic magnet.
2. The north pole of a freely suspended magnet settles in the direction of the geographic north pole of the earth since unlike poles attract.
3. It means that the south pole of some gigantic magnet must be near the geographic north pole of the earth.
4. In other words, the thing we call Earth’s geographic north pole is actually the south pole of the magnet inside the earth.
5. That is why a freely suspended magnet always settles in geographic north-south attracted by opposite poles of the earth as a great magnet.

Question 2.
Which magnetic poles attract each other?
Answer:
Opposite magnet poles attract each other.

Question 3.
Which pole of a spherical magnet will get attracted towards the south pole of the bar magnet?
Answer:
The north pole of the spherical magnet will get attracted towards the south pole of the bar magnet.

Question 4.
Why does a bar magnet kept at a distance doesn’t attract pins?
Answer:

1. The region around the magnet where the magnetic force acts is known as the magnetic field.
2. It has its influence over a certain distance where these magnetic lines of force act.
3. As these pins are outside this area of influence, a bar magnet does not attract those pins which are at a distance.

Question 5.
What is an electromagnet?
Answer:

1. A soft metal core made into a magnet by the passage of electric current through a coil surrounding it is called an electromagnet.
2. An electromagnet is a magnet in which the magnetic field is produced by electricity.
3. The strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it.
4. The poles of an electromagnet can even be reversed by reversing the flow of electricity.
5. An electromagnet works because an electric current produces a magnetic field.
6. The magnetic field produced by electric current forms circles around the electric current.
7. The magnetic field disappears when the current is turned off.

Question 6.
How can an electromagnet be made?
Answer:

1. It is easy to make an electromagnet. To make an electromagnet we needs an iron nail of 10 cm length 1 metre long insulated copper wire, a battery cell, pins.
2. Neatly wrap some insulated copper wire around an iron nail.
3. The more wires you wrap around the nail, the stronger will be the electromagnet.
4. Attach a battery to the wire, an electric current will begin to flow and the iron nail will become magnetised.
5. When the battery is disconnected the iron nail will lose its magnetism.

Use your brainpower!

Answer the following questions:

Question 1.
Which direction will a magnetic needle show on the geographic north pole?
Answer:
North, all magnetic needle will show north direction.

Question 2.
Is magnetic force a vector or a scalar quantity?
Answer:

1. It is a vector quantity. Because a magnetic field is the magnetic effect of electric current and magnetic materials.
2. The magnetic field at any given point is specified by both direction and magnitude as such it is represented by a vector field.

Question 3.
What is meant by magnetic force?
Answer:

1. The magnetic force, is a consequence of the electromagnet force, one of the four fundamental forces of nature.
2. It occurs whenever objects interact in which there is charge in motion, eg. compass, a motor.
3. Magnetic force is an attraction or repulsion that arises between electrically charged particles because of their motion.

Question 4.
How does a magnetic force act without direct contact?
Answer:
Magnetic force acts without even direct contact because of the penetrating ability of the magnetic field.

Question 5.
What is the difference between the gravitational force and magnetic force?
Answer:

Gravitational Force	Magnetic Force
1. Gravitational force acts between any objects with mass.	1. Magnetic force acts between objects with specific properties.
2. It depends on the mass of the objects.	2. It does not depend on the mass of objects.
3. It acts over long-range as a gravitational field is large.	3. It acts over short-range as magnetic field is short.
4. Object are always attracted to each other.	4. Objects are either attracted or repelled.

Question 6.
Why is repulsion the real test for identifying a magnet?
Answer:
A magnet can attract the opposite pole of the magnet as well as magnetic substances (iron, cobalt, nickel).
So if a magnet attracts another object, we cannot say that other object is a magnet or a magnetic substance.
But if the magnet repels the object then we can surely say that the other object is a magnet because like poles of magnets repel each other.

Question 7.
How will you find a magnet from among the various articles given to you?
Answer:

1. Magnet has the property to attract things made of iron, cobalt, nickel.
2. A magnet has magnetic field which is invisible but it has the property of attracting, pulling other
3. ferromagnetic material such as iron, cobalt and nickle.
4. So if we bring any iron, nickle objects near it, they will be pulled toward the magnet.
5. The real test is repulsion.
6. The article which shows repulsion when one of the poles of a magnet is brought near is surely a magnet.

Find out:

Answer the following questions:

Question 1.
Why does the magnetic needle of a compass not settle parallel to the ground but at an angle to it?
Answer:

1. Freely suspended magnet does not point to north, but aligns to earth’s magnetic field axially ie – north-south.
2. The magnetic pole of the earth is different from true north (geographic north) because the magnetic north is constantly changing.
3. It leads to a margin of error called declination in which there is an angle of difference (11.51)° between Magnetic North and True North.
4. That is the reason the magnetic needle does not settle parallel to the ground.

Observe the diagrams and answer the questions given below:

Question 1.
Name the methods shown.
Answer:
Single touch and Double touch methods of magnetising a steel bar.

Question 2.
Give 2 points of difference between the methods.
Answer:

Single touch method	Double touch method
1. In this method, one magnet is used to magnetise the steel bar.	1. In this method, two magnets are used to magnetise the steel bar.
2. In this method, the magnet is dragged from one end of the steel bar to another end.	2. In this method, two magnets are dragged from the middle of the steel bar to the opposite directions.
3. As only one magnet is used to induce magnetism, this method is called single touch method.	3. As two bar magnets are used to induce magnetism, this method is called double-touch method.
4. The magnetism created by this method is of low strength and lasts for a short time.	4. The magnetism created by this method is of high strength and lasts for a longer time.

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 3 Diversity in Living Things and their Classification Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 6 Science Solutions Chapter 3 Diversity in Living Things and their Classification

Class 6 Science Chapter 3 Diversity in Living Things and their Classification Textbook Questions and Answers

1. Match the pairs.

diversity in living things and their classification class 6 exercise Question 1.

Column ‘A’	Column ‘B’
1. Amphibians	a. A monkey
2. Vertebrates	b. A snake
3. With scales	c. A frog

Answer:

Column ‘A’	Column ‘B’
1. Amphibians	c. A frog
2. Vertebrates	a. A monkey
3. With scales	b. A snake

2. Who is the odd one out?

Question a.
Fungus, mushroom, chrysanthemum, spirogyra
Answer:
Chrysanthemum (only flowering plants)
or
Spirogyra (only aquatic plant)

Question b.
Mango, banyan, palm, chickpea
Answer:
Chickpea (shrub, others are not)
or
Palm (tall tree without any branches, others have branches)

Question c.
Grape, orange, lemon, hibiscus
Answer:
Grape (only creeper, others are not)
or
Hibiscus (flower, others are fruits)

Question d.
Sunflower, banyan, jowar, bajra
Answer:
Banyan (perinnial, others are not)

Question e.
Guava, radish, carrot, beetroot
Answer:
Gauva (fruit, others are roots)

Question f.
Deer, fish, man, worms
Answer:
Worms (invertebrate, others are not)
or
Fish (aquatic animal, others are terristrial animals

3. What is the difference?

Question a.
Flowering plant and Non-flowering plant
Answer:

Flowering plant	Non-flowering plant
1. Plants that bear flowers are called flowering plants.	1. Plants that do not bear flowers are called non­flowering plants.
2. They have roots, stems and leaves.	2. They may not have roots, stems or leaves.
e.g. Rose, sunflower, lotus	e.g. Pine, fern, algae

Question b.
A Tree and a Shrub
Answer:

Tree	Shrub
1. They have branches at some height above the ground.	1. They give out branches close to the ground.
2. They grow very tall compared to shrubs.	2. They grow upto 2 to 3 metres in height.
3. They have strong and hard stems.	3. They have thick hard stems.
e.g. Mango tree, banyan tree	e.g. Hibiscus, oleander

Question c.
Vertebrates and Invertebrates
Answer:

Vertebrates	Invertebrates
1. They have vertebral column.	1. They do not have vertebral column.
2. The brain is well developed.	2. The brain if present may not be developed.
e.g. Human, dog, fishes etc.	e.g. earthworm, insects etc.

4. True or false?

Question a.
The snail is an aquatic animal.
Answer:
False

Question b.
Amphibians can live in air and in water.
Answer:
False

Question c.
The function of the brain is well developed in vertebrate.
Answer:
True

Question d.
The amoeba is a multicellular animal.
Answer:
False

5. Write two names of each. 

Question a.
A flowering plant
Answer:
Rose, hibiscus

Question b.
A non-flowering plant
Answer:
Fern, algae

Question c.
A tree
Answer:
Mango, banyan

Question d.
A shrub
Answer:
Oleander, hibiscus

Question e.
A creeper
Answer:
Pumpkin, watermelon

Question f.
An annual plant
Answer:
Jowar, sunflower

Question g.
A biennial plant
Answer:
Carrot, beetroot

Question h.
A perennial plant
Answer:
Mango, gulmohar

6. Write answers to the following. 

Question a.
What are the parts of a plant?
Answer:
The parts of a plant are: root, stem, leaves, flowers, fruit and seed.

Question b.
What are the functions of root?
Answer:
The functions of root are:

1. The root hold the soil firmly and anchor the plant.
2. They absorb water, salt and minerals from the soil and transport it to stem.
3. Some roots store food. e.g. Carrot, radish.

Question c.
Why is it necessary to classify living things?
Answer:

1. There is a great diversity in living things- both plants and animals on the earth.
2. In order to identify them and to study their characteristics, systematic classification is necessary.

Question d.
What are the criteria used to classify living things?
Answer:
Following are the criteria used to classify living things:
a. Plants:

• Mode of nutrition.
• Similarities and differences in structure.
• Presence of flowers or not.
• Period of life cycles.
• Habitat.

b. Animals:

• Cell structure.
• Presence of vertebral column.
• Method of reproduction.
• Habitat.

Question e.
Tell some characteristics of creepers.
Answer:
The characteristics of creepers are:

1. The stem of a creeper is very flexible, soft and green and need support to climb.
2. Some climbers spread on the ground, e.g. Pumpkin
3. Some have aerial roots, e.g. Money plant
4. Some climbers develop tendrils, e.g. Cucumber

Question f.
Explain the characteristics of herbs with examples.
Answer:

1. Herbs grow 1 to 1.5 m tall.
2. Their stem is green and quite flexible.
3. They may live for a few months or upto two years, e.g. Tulsi, oregano, etc.

Question g.
How is the body of animals protected?
Answer:
Body of animals are protected by special covering such as skins, feathers, scales, hair fur, etc.

Question h.
On the basis of which criteria will you classify plants and animals?
Answer:

7. Draw figures. 

Question a.
Draw the figure of a plant to show the parts, namely, the root, stem and leaves in it.
Answer:

Activity:

Question 1.
Visit a plant nursery and classify the plants there.

Question 2.
Visit a zoo and obtain information about the diversity in animals.

Question 3.
Write an essay on diversity in plants.

Question 4.
Collect seeds of various plants during summer and throw them in open spaces (fallow land, moorland, hill, etc.) during the rainy season.

Class 6 Science Chapter 3 Diversity in Living Things and their Classification Important Questions and Answers

Fill in the blanks:

Question 1.
Plants that can prepare their own food are called ………….. plants.
Answer:
autotrophic

Question 2.
Pitcher plants are ………….. .
Answer:
insectivorous

Question 3.
The ………….. is an important means of reproduction.
Answer:
flower

Question 4.
Animals that lay eggs are ………….. animals.
Answer:
oviparous

Question 5.
Animals that can live on land as well as water are called ………….. .
Answer:
amphibians

Choose the correct alternative:

Question 1.
The ………….. is a perennial.
(a) beetroot
(b) gulmohar
(c) grass
Answer:
(b) gulmohar

Question 2.
The sunflower is a / an ………….. plant.
(a) annual
(b) biennial
(c) perennial
Answer:
(a) annual

Question 3.
Cactus is a ………….. plant.
(a) land
(b) water
(c) desert
Answer:
(c) desert

Question 4.
The …………….. is a unicellular animal.
(a) cockroach
(b) snail
(c) paramoecium
Answer:
(c) paramoecium

Question 5.
Hen is a …………….. animal.
(a) oviparous
(b) viviparous
(c) none of above
Answer:
(b) oviparous

Question 6.
Earthworm is a / an ……………. animal.
(a) vertebrate
(b) invertebrate
(c) unicellular
Answer:
(b) invertebrate

True or False:

Question 1.
The pods of beans and peas are actually fruits.
Answer:
True

Question 2.
Fungus is heterotrophic.
Answer:
True

Write two names of each.

Question 1.
An invertebrate animal
Answer:
Earthworm, cockroach

Question 2.
An oviparous animal.
Answer:
Hen, sparrow

Distinguish between:

Question 1.
Autotrophic plant and Heterotrophic plant
Answer:

Autotrophic plant	Heterotrophic plant
1. They can produce their own food.	1. They cannot produce their own food. They depend on other things for their food.
2. They are green in colour.	2. They are non­green in colour.
e.g. Periwinkle, pomegranate etc.	e.g. Dodder, loranthus etc

Classify as directed.

Question 1.
Into annual, biennial, perennial
Sunflower, carrot, bajra, mango, jowar, oleander, beetroot, coconut
Answer:

Annual	Biennial	Perennial
Sunflower	Carrot	Mango
bajra	beetroot	oleander
jowar		coconut

Question 2.
Into vertebrates and invertebrates
Fish, cat, earthworm, snail, hen, cockroach
Answer:

Vertebrates	Invertebrates
Fish	Earthworm
cat	snail
hen	cockroach

Define. 

Class 6 Science Chapter 3 Diversity In Living Things and Their Classification Question 1.
Unicellular animal
Answer:
Animals which have a single cell body performing all functions, are called unicellular animals, e.g. Amoeba

Diversity In Living Things And Their Classification Exercise Question 2.
Multicellular animals
Answer:
Animals which have many cells in their body, are called multicellular animals, e.g. Cat

Diversity In Living Things and Their Classification Question 3.
Vertebrates
Answer:
Animals with vertebral column are called vertebrates, e.g. Man

Question 4.
Invertebrate animals
Answer:
Animals without vertebrate column are called invertebrate animals, e.g. Earthworm

Question 5.
Oviparous animals
Answer:
Animals which lay eggs and hatch them are called oviparous animals, e.g. Hen

Question 6.
Viviparous animals
Answer:
Animals which give birth to their young ones are called viviparous animals, e.g. Dog

Answer the following:

Question 1.
Give the functions of:
Answer:
a. Stem:
1. The stem gives support to the other parts of the plant.
2. The stem carries out the function of production, conduction and storage of the food.
3. In some cases it stores food.
b. Leaves: They play an important role in the production of food.
c. Flowers: The flowers are reproductive organ of plant.
d. Fruits: Fruits have seeds which give rise to new plant.
e. Seeds: From the seeds arise new plants.

Answer the following in short.

Question 1.
What type of plants are toolstools and mushrooms?
Answer:
Toolstools and mushrooms are heterotrophs.

Question 2.
What type of plant is a fig?
Answer:
Fig is a tree.

Question 3.
Do ferns, algae and money plant bear flowers?
Answer:
Ferns, algae and money plants do not bear flowers. They are non-flowering plants.

Question 4.
Which is the largest flower and where is it found?
Answer:
Rafflesia Arnoldi is the world’s largest flower. It is found in Indonesia.

Question 5.
Where does pomegranate grow?
Answer:
Pomegranate is a shrub which grows on land in soil.

Question 6.
Where do bulrushes and railroad creepers grow?
Answer:
Bulrushes is a water plant and railroad creepers grow along the ground.

Question 7.
Where does lotus grow?
Answer:
Lotus grows in water.

Question 8.
Where does the dodder plant grow?
Answer:
Dodder is a parasitic plant and grows on other plants.

Question 9.
Why does water hyacinth float?
Answer:
The stem of water hyacinth is filled with air and its leaves are specially modified, which helps it to float in water.

Question 10.
Why is the stem of a cactus plant fleshy?
Answer:
Cactus is a desert plant. As there is a shortage of water, cactus stores water in its stem and hence, stem of cactus is fleshy.

Question 11.
Which spheres of the earth do living things exist?
Answer:
Living things exists in all three spheres of earth, i.e. Atmosphere, lithosphere and hydrosphere.

Question 12.
Are the plants and animals that you have seen all alike?
Answer:
No. They are all of different types.

Question 13.
What are the similarities between a mango, a banyan and a tamarind tree?
Answer:
They are tall, big and perennial plants.

Question 14.
What are the similarities between the hibiscus, oleander and lantana plants?
Answer:
They are shorter and smaller than trees.

Question 15.
What are the similarities between fenugreek and periwinkle plants?
Answer:
They are smaller and shorter than trees and shrubs.

Question 16.
Have you seen vines like the pumpkin, the railroad creeper, kavali, watermelon or the grapvine? How do they grow?
Answer:
They have very soft, green and flexible stem. They grow with the help of a support.

Question 17.
For how many years do crops like bajra, wheat, corn, radish, marigold live?
Answer:
They live for about one year.

Question 18.
To which part of plants are butterflies and insects attracted?
Answer:
Butterflies and insects are attracted towards the flower of the plants.

Question 19.
What is the chain of bones in the centre of our back called?
Answer:
A vertibral column.

Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 7 Nutrition and Diet Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 6 Science Solutions Chapter 7 Nutrition and Diet

Class 6 Science Chapter 7 Nutrition and Diet Textbook Questions and Answers

1. Fill in the blanks:

Question a.
The process of intake of food and utilizing it for all life processes is called ……………. .
Answer:
nutrition

Question b.
All the substances in our food which are useful for various body processes are called ………… .
Answer:
nutrients

Question c.
Carbohydrates and …………. provide …………… to our body.
Answer:
fats, energy

Question d.
In a balanced diet, all the nutrients are present in the ……………. proportion.
Answer:
right

Question e.
In the food pyramid, cereals are given the maximum space because they fulfill our …………… requirement.
Answer:
energy

Question f.
Intake of more food than necessary causes ………….. .
Answer:
overnutrition

2. Spot the following in the table of vitamins and minerals.

Question a.
The nutrient present in citrous fruits.
Answer:
Vitamin C

Question b.
Vitamins/minerals present in milk.
Answer:
Vitamin A, Vitamin B, Vitamin D, calcium, phosphorus.

Question c.
Causes and symptoms of night blindness, scurvy, rickets, beriberi.
Answer:

Diseases	Causes	Symptoms
1. Night blindness	Deficiency of Vitamin A	Inability to see in dim light
2. Scurvy	Deficiency of Vitamin C	Bleeding of gums
3. Rickets	Deficiency of Vitamin D	Softening of bones
4. Beri-beri	Deficiency of Vitamin B1	Nerve disorder, muscle weakness

Question d.
Foods required to prevent the above diseases.
Answer:

Diseases	*Causes	‘Symptoms	Food for prevention
1. Night blindness	Deficiency of Vitamin A	Inability to see in dim light	Carrots, milk, dark green vegetables.
2. Scurvy	Deficiency of Vitamin C	Bleeding of gums	Amla, kiwi, oranges and citrus fruits.
3. Rickets	Deficiency of Vitamin D	Softening of bones	Exposure to sunlight, milk, fish, egg, butter.
4. Beri-beri	Deficiency of Vitamin B1	Nerve disorder, muscle weakness	Milk, fish, meat, cereals, nuts, pulses

Question e.
Causes of anaemia.
Answer:
Deficiency of Vitamin B₁₂, iron.

Question f.
Essential mineral for healthy bones and teeth.
Answer:
Calcium, phosphorus.

Question g.
Sensory organ affected due to the deficiency of Vitamin A.
Answer:
Eyes, skin.

3. Choose the correct alternative. 

Question a.
Pulses are a very good source of ……………. .
(1) carbohydrates
(2) proteins
(3) fats
(4) minerals
Answer:
(2) proteins

Question b.
…………. provide maximum energy to our body.
(1) Cereals
(2) Leafy Vegetables
(3) Water
(4) Amla
Answer:
(1) Cereals

Question c.
Goitre is caused by the deficiency of ……….. .
(1) iron
(2) calcium
(3) iodine
(4) potassium
Answer:
(3) iodine

Question d.
……….. is a type of junk food.
(1) Orange
(2) Milk
(3) Bhakri
(4) Chocolate
Answer:
(4) Chocolate

4. Use the food pyramid to select food items of your choice for three days.
Conditions:
1. The diet for all three days should be balanced.
2. There should be variety in the items chosen for the three days.
Answer:

Day 1:
Cereal like cornflakes and milk, apple, roti, sabzi and dal.

Day 2:
Bread and butter with milk, rice/ roti and chicken, curd, any one type of fruit, salad.

Day 3:
Poha, green vegetable and dal with rice or roti, raita, one fruit, vegetable sandwich.

Activity:

Question 1.
Obtain information on simple methods of spotting the adulteration in foodstuffs and try them out.

Class 6 Science Chapter 7 Nutrition and Diet Important Questions and Answers

Choose the correct alternative:

Question 1.
Vitamin ……………. and vitamin …………….. dissolve easily in water.
(a) A, B
(b) B, C
(c) B, D
(d) B, E
Answer:
(b) B, C

Question 2.
……………. carries oxygen to all parts of the body.
(a) Calcium
(b) Iron
(c) Iodine
(d) Sodium?
Answer:
(b) Iron

Question 3.
Deficiency of vitamin ……………. causes excessive bleeding after an injury.
(a) A
(b) B
(c) K
(d) D
Answer:
(c) K

Question 4.
In accordance with the food pyramid, the proportion of ……………. should be least in our diet.
(a) cereals
(b) fruits
(c) milk
(d) oil
Answer:
(d) oil

Question 5.
……………. is a rich source of vitamin C.
(a) Carrot
(b) Amla
(c) Meat
(d) Milk
Answer:
(b) Amla

Question 6.
Children of growing age need to get approximately ……………. to ……………. calories from the food they eat.
(a) 1500-2000
(b) 3150-4150
(c) 2000-2500
(d) All of them
Answer:
(c) 2000-2500

Fill in the blanks:

Question 1.
All food that we consume during the day is together called our ………. .
Answer:
diet

Question 2.
………….. convert milk into yogurt.
Answer:
Probiotics.

Match the columns:

Question 1.

Column ‘A’	Column ‘B’
1. Carbohydrates	a. resistance to diseases
2. Proteins	b. energy
3. Fibre	c. growth
4. Vitamins	d. excretion

Answer:

Column ‘A’	Column ‘B’
1. Carbohydrates	b. energy
2. Proteins	c. growth
3. Fibre	d. excretion
4. Vitamins	a. resistance to diseases

Question 2.

Column ‘A’	Column ‘B’
1. Iron	a. Goitre
2. Calcium and phosphorous	b. Anaemia
3. Iodine	c. Inefficiency of muscles
4. Sodium and potassium	d. Weak bones

Answer:

Column ‘A’	Column ‘B’
1. Iron	b. Anaemia
2. Calcium and phosphorous	d. Weak bones
3. Iodine	a. Goitre
4. Sodium and potassium	c. Inefficiency of muscles

Question 3.

Column ‘A’	Column ‘B’
1. Vitamin A	a. Scurvy
2. Vitamin C	b. Excessive bleeding
3. Vitamin D	c. Skin disorders
4. Vitamin E	d. Nightblindness
5. Vitamin K	e. Rickets

Answer:

Column ‘A’	Column ‘B’
1. Vitamin A	d. Nightblindness
2. Vitamin C	a. Scurvy
3. Vitamin D	e. Rickets
4. Vitamin E	c. Skin disorders
5. Vitamin K	b. Excessive bleeding

Pick out the odd one:

Question 1.
Chocolate, chapatti, banana, milk
Answer:
Chocolate

Question 2.
Rice, chapatti, carrot, dal.
Answer:
Carrot

Question 3.
Scurvy, Rickets, Beriberi, Goitre.
Answer:
Goitre

Question 4.
Vitamin A, Vitamin C, Vitamin D, Vitamin E
Answer:
Vitamin C

Answer the following:

Question 1.
Why do living things need food and water?
Answer:
Living things take food and water and use them for:

1. Obtaining energy
2. Growth of the body
3. Carrying out day to day functions of the body.
4. Fighting against diseases

Question 2.
Name the main nutrients in our food.
Answer:
There are six main nutrients in our food. They are:

1. Carbohydrates
2. Fats
3. Proteins
4. Fibres
5. Vitamins
6. minerals

Question 3.
How do we get energy from the food?
Answer:

1. We get energy in the form of heat from the food we eat.
2. Heat is measured in kilocalories (calories).
3. Hence, the energy in food items is also measured in kilocalories (calories).

Question 4.
Vitamin C rich food should be eaten raw. Why?
Answer:

1. Vitamin C is very sensitive to heat and light.
2. It is destroyed easily during cooking. Hence, Vitamin C rich food should be eaten raw.

Question 5.
What is balanced diet? Give its significance.
Answer:
A diet containing adequate quantities of all nutrients is called as balanced diet. Significance of a balanced diet are:

1. An increased capacity to work.
2. Good physical and mental health.
3. Increased capacity to fight/resist diseases.
4. Helps in proper growth of the body.

Question 6.
What is obesity? How to avoid obesity?
Answer:

• Obesity is the state of being overweight.
• Junk food eaten frequently causes obesity.
• Obesity is not good for health.

To avoid obesity:

1. Have a balanced diet.
2. Eat whole grains, fruits and vegetables with their skins.
3. Increase use of bicycles.
4. Play more outdoor games.
5. Do not eat if you are not hungry.
6. Do not watch T.V while eating.
7. Avoid precooked, packaged food.
8. Exercise regularly.

Write short notes.

Question 1.
Vitamins:
Answer:
1. Vitamins are vital substances required by our body in small quantities. They help to improve the body’s resistance to diseases. Their deficiency can lead to various diseases, e.g.: deficiency of Vitamin A causes night blindness and that of Vitamin D causes rickets. The sources of vitamins are vegetables, fruits, milk, fish, meat etc.
2. There are two kinds of vitamins – water soluble vitamins and water insoluble vitamins.
3. Vitamin B and Vitamin C are water soluble vitamins because they dissolve easily in water. They are thrown out of the body through the water in sweat and urine. Hence, a regular supply of these vitamins is essential. B₁₇B₂, B₃, B₆, B₉, and Bp are the types of vitamin B.
4. Vitamins A, D, E and K are insoluble in water but are fat soluble vitamins. They get stored in the body.

Question 2.
Probiotics:
Answer:

1. The useful microorganisms which convert milk into yoghurt are present in yoghurt and buttermilk are called probiotics.
2. Lakhs of such useful microorganisms are present in our intestine.
3. They are essential for our health.
4. Hence, to maintain them in our body we should include food rich in probiotics in our daily diet.

Question 3.
Junk food:
Answer:

1. Foods which gives us energy but do not supply the necessary nutrients are called junk food.
2. Foods like chocolate, pizzas, burgers, noodles, fried foods like pakodas are junk food.
3. These foods contain refined flour, sugar and oil in large proportion.
4. If we consume these foods frequently, our body experiences shortage of proteins, vitamins and minerals.
5. This may lead to malnutrition and obesity.

Question 4.
Adulteration of food:
Answer:
To earn more profits, cheaper substances of low quality called adulterants, are mixed with the foodstuffs. The mixing adulterants to foodstuffs is called adulteration of food. Adulterants may be poisonous or harmful and such food is impure and unfit for consumption.
Some of the adulterants added to foodstuffs are given below:

Give scientific reasons:

Question 1.
Deficiency of vitamin B and C are common in our body.
Answer:

1. Vitamin B and vitamin C are water soluble vitamins.
2. They are thrown out of the body through the water in sweat and urine.
3. Hence, a regular supply of these vitamins is essential.
4. If we don’t intake food rich in these vitamins, deficiency occurs.

Question 2.
Exposure to sunlight is essential.
Answer:

1. On exposure to sunlight our body synthesizes Vitamin D from substances in milk, fish, eggs and butter.
2. Its deficiency causes softening of bones (Rickets).
3. Vitamin D helps in absorbing calcium and phosphorous for healthy bones and teeth.
4. Hence, exposure to sunlight is essential.

Complete the tables given below:

1.

Nutrients	Source	Function
1. Carbohydrates	Rice, chapatti	Provide energy
2. Fats	Oil, butter	Provide energy
3. Proteins	Sprouts, meat, eggs	Growth, repairing wear and tear of the body.
4. Vitamins	Vegetables, fruits	Improve body’s resistance to diseases
5. Fibre	Sprouts, vegetable, fruits	Help in excretion

2.

Mineral	Source	Function
1. Iron	Spinach, raisins	Carrying oxygen to all parts of the body
2. Calcium, phosphorous	Milk, milk products, meat	Strengthen bones and teeth
3. Iodine	Raisins, fish, sea fish	Controls growth, speeds up chemical reactions in the body.
4. Sodium and potassium	Salt, leafy vegetables, fruits, pulses	Maintain the body’s water balance and functioning of the muscles and nervous system.

3.

Vitamins	Source	Function
1. A	Carrot, milk, vegetables	Protects eyes, helps to keep skin, bones and teeth healthy.
2. B1	Milk, fish, cereals	Helps in proper function of nerves and heart.
3. B9	Deep green vegetables, papaya, kiwi	Growth of the body
4. B12	Meat, milk products	Formation of red blood cells
5. C	Amla, citrus fruits, green leafy vegetables	Protects body tissues
6. D	On exposure to sunlight, Vitamin D is made in our body	Formation of collagen – a protein essential for gums, teeth, bones and skin
7. E	Green  leafy vegetables, vegetable oil	Metabolism, reproduction
8. F	Green  leafy vegetables, sprouted pulses, yellow of egg	Helps in clotting of blood

Using the food items given below, prepare a balanced diet pyramid.
[Chapatti, banana, carrot, butter, Nan, egg, bread, cheese, dal, spinach, milk]
Answer:

Can you recall?

Question 1.
Which are the various groups of foodstuff? Which main constituents of food do we get?
Answer :
The various groups of foodstuffs are:

1. Milk and milk products, meat, fish, eggs.
2. Cereals and pulses
3. Vegetables and fruits.
4. Fatty substances oil, butter and ghee.

There are six main nutrients in our food: carbohydrates, fats, proteins, fibres, vitamins and minerals.

Nutrients	Foodstuffs
1. Carbohydrates	Cereals and pulses
2. Protein	Milk product, meat, fish, eggs
3. Fats	Butter, oil, ghee
4. Fibres	fruits and vegetables

Question 2.
What trouble do we have to face if we do not get enough fibre from our daily diet?
Answer:
Fibres help in excretion of food, if we do not get enough fibre we will face indigestion and stomach-ache.

Question 3.
What care must be taken to make sure that fibre is not lost or removed from the food we get?
Answer:
We must not over-cook the foodstuff containing fibres. Fruits should be eaten raw.

Balbharti Maharashtra State Board Class 8 English Solutions Chapter 1.1 A Time To Believe Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 8 English Solutions Chapter 1.1 A Time To Believe

Class 8 English Chapter 1.1 A Time To Believe Textbook Questions and Answers

Warming Up:

Question 1.
Think, choose and fill up the labels with what a ‘sunrise’ symbolizes.
(jewellery / art / hope / birth / anger / new opportunities / good manners / inspiration/ new achievements / happiness / misery / bright moments / new aims / money / newsurprises)

Answer:

Question 2.
An acrostic is a poem or a write up in which the first letter of each line forms a word, when it is read vertically. Complete the acrostics of BELIEVE and FAITH.

With your benchmate / group, complete the acrostic of BELIEVE and FAITH.
Answer:

1.A. Rearrange the letters to make meaningful words, occurring in the poem.

1. clearmis
2. sowmid
3. tabyue
4. madres
5. laveu
6. downre

Answer:

1. miracles
2. wisdom
3. beauty
4. dreams
5. value
6. wonder

1.B. Write words from the poem that describe the following.

1. sky
2. heart
3. hand
4. beginning

Answer:

1. stardust sky
2. nurturing heart
3. aging hand
4. new beginning

2. Say WHY. . . . .

Question a.
________ the sky has a magical quality.
Answer:
The sky has a magical quality because it has scurrying clouds, twinkling stars and a beautiful moon.

Question b.
_______ even an aging hand has beauty.
Answer:
because it can teach us how to love.

Question c.
_______we should believe that we are strong and courageous.
Answer:
We should believe that we are | strong and courageous so that we can recover after we have gone through difficulties and shocks, and return to our normal lives again.

3. Make a list of any six things that the poet wants us to accept as true.
Answer:
The poet wants us to accept as j true the following things :

• that we have the strength and ( courage to get back to normal after a setback
• that we are never alone
• that life is a gift we must cherish
• that there are wonderful surprises in store for us
• that all our hopes and dreams are within reach
• that great things will happen if we have belief in life and in ourselves

4. Find from the poem, positive qualities to fill up the web.

Answer:

5. Read the lines below.
(A) ‘To believe is to see angels dancing among the clouds’.
The above line contain a human characteristic ‘dancing’ given to something
non – human, ‘angels’. The Figure of Speech used in the line is called
‘Personification’.

(B) ‘To believe is to know that
Everyday is a new beginning’.

(C) To believe is to know ………. life is a gift
Lines in poetry, such as the above, state a general truth and can be used as sayings or
quotes etc. They contain the Figure of Speech called Epigram.
Epigram closely resembles a proverb.

Find from the poem three other examples of Epigram.
Answer:
(i) ‘To believe is to find the strength and courage that lies within us.’
(ii) ‘To believe is to know we are never alone, that life is a gift.’
(iii) ‘To believe is to know that wonderful surprises are just waiting to happen.’
(These lines state a general truth.)

6. Divide the class into 5 groups. Each group can prepare a decorative chart / poster using an epigrammatic lines from the poem. You may use calligraphy / painting / or Paint programme on a computer. (With permission, put up these charts in your school.)

Class 8 English Chapter 1.1 A Time To Believe Additional Important Questions and Answers

Complete the following:

Question 1.
One should know and trust _______.
Answer:
One should know and trust that every day is a new beginning, that miracles happen and dreams really do come true.

Question 2.
The two supernatural references in the second stanza _______.
Answer:
The two supernatural references in the second stanza are to angels and to the man in the moon.

Activities based on Poetic Devices/Vocabulary:

Question 1.
Find out an example of Personification from the extract.
Answer:
‘To believe is to see angels dancing among the clouds.’ (Here, the angels have been given the human quality of ‘dancing’.)

Question 2.
Pick out examples of Alliteration from the extract.
Answer:
(i) …. and the wisdom of the man in the moon’. (Repetition of the sound of the letter ‘m’.)
(ii) For it is through their teachings, we learn to love. (Repetition of the sound of the letters ‘t’ and T.)

Question 3.
Pick out an example of Repetition from the extract.
Answer:
The words ‘To believe is to ….’ are repeated at the beginning of each stanza. This provides emphasis to the message in the poem and gives rhythm to the stanzas.

Complete the following:

Question 1.
The two qualities that are needed to recover after a shocking event are _________.
Answer:
strength and courage.

Question 2.
The poet advises everybody to ______.
Answer:
have a positive attitude.

Complex Factual Activities:

Question 1.
Explain why ….
…. we should believe that we are strong and courageous,
Answer:
We should believe that we are strong and courageous so that we can recover after we have gone through difficulties and shocks, and return to our normal lives again.

Activities based on Poetic Devices/Vocabulary :

Question 1.
Rearrange the letters to form meaningful words occurring in the extract.

1. gearuoc
2. rissupser
3. gnehtrts
4. irehchs

Answer:

1. courage
2. surprises
3. strength
4. cherish

Question 2.
Write word from the extract that describe the following :
surprises
Answer:
wonderful surprises

Question 3.
Pick out an example of Metaphor from the extract.
Answer:
‘That life is a gift.’ Life is implicitly compared to a gift.

Question 4.
Pick out an example of Repetition from the extract.
Answer:
The words ‘To believe is to ….’ are repeated at the beginning of each stanza. This provides emphasis to the message in the poem and gives rhythm to the stanzas.

Question 5.
Analysis/Appreciation Of The Poem ‘A Time To Believe’
Answer:
Poem and poet: ‘A Time to Believe’ by B.J. Morbitzer.
Theme: To believe in ourselves and to have a positive and optimistic attitude towards life.
Tone: Serious and inspirational.
Structure and stanzas: 4 lines in each stanza, except in the last stanza, which has 5 lines.
Rhyme and Rhythm: No rhyme scheme; the poem is written in free verse.
Language and Imagery: The language is simple and direct. The only instances of Imagery are of ‘angels dancing among the clouds’ and the ‘stardust sky’.
Figures of Speech: Personification, Epigram, Repetition, Metaphor.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 16 Natural Resources Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 16 Natural Resources

Class 7 Science Chapter 16 Natural Resources Textbook Questions and Answers

1. Describe natural resources with reference to the following 3 types:

Question a.
Mineral resources
Answer:
Mineral wealth has an important place among natural resources. The rocks on the earth are mainly made of minerals. These minerals can be obtained by mining. Minerals that contain a high proportion of metals are ores, (i) Minerals are formed from the magma in the earth’s crust and the lava from the eruption of volcanoes when they cool and get transformed into crystals e.g. magnetite, mica, (ii) Minerals get transformed from one form into another due to large changes in temperature and pressure e.g. Diamond, Graphite, (iii) There are 3 types of minerals according to their properties Non-metal minerals: e.g. mica, sulphur, potash, diamond.

• Metals minerals: e.g. Iron, gold, silver, tin, bauxite, platinum.
• Energy minerals: e.g. Coal, mineral oil, natural gas, diamond, ruby, sapphire, jade are used as gems.

Some important minerals and ores are Iron ore, manganese, bauxite, copper and mica.

Question b.
Forest resources
Answer:

1. A forest is a natural habitat of plants, animals and microbes.
2. Forest perform certain specific protective and productive functions.
3. We get different types of wood and many medicinal plants from forests.
4. Forest wealth includes fire wood, trees like teak, mahogany, neem, acacia, subabhul, fibers, paper, rubber, gum, aromatic substances.
5. We get fragrant essential oils from lemon grass, vanilla, kewada, vetiver (khus) and eucalyptus.
6. Sandalwood and oil of eucalyptus are used for making soaps, cosmetics and incense sticks.
7. Also we get fruits, bulbs, roots, honey, sealing wax, dyes from forest.
8. Many medicinal plants adulsa, bel, neem, periwinkle, cinnamon, are used for treatment of various diseases such as cough cold, malaria, diarrhoea, cancer, fever and cold.
9. Wood is used as a source of energy for cooking purpose and for keeping warm.
10. For making furniture, tool handles, matches, bridges, boats etc.
11. Bamboos are used for matting, flooring, basket, ropes, rafts, cots etc.
12. Bamboos, wood are used in the manufacture of rayon, yams, artificial silk-fibers.

Question c.
Ocean resources
Answer:

1. Oceans occupy about 70% of a earth’s surface.
2. Energy can be obtained on a large scale from oceans.
3. Sea waves at high and low tide and ocean currents are being used for generation of power.
4. There are billions of tons of minerals dissolved in ocean water.
5. There are large reserves of tin, chromium, potassium, phosphates, copper, zinc, iron, lead, thorium, manganese, sulphur, uranium in the ocean and sea beds.
6. Also we get many types of gems, conches, shells and pearls from the sea.
7. There are large reserves of mineral oil and natural gas at the bottom of sea.
8. We get fishes, dried shrimp, shells, fungi, shark, cod fish and sea cucumber from the ocean.

2. Write answers to the following questions in your own words.

Question a.
What is meant by fossil fuel? What are their types?
Answer:

1. Fossil fuels (such as coal or natural gas) are formed in the earth from dead plants and animals, due to high pressure from above and the heat from the earth’s interior.
2. The dead plants, animals get transformed into fossil fuel.
3. There are three types of fossil fuels which can be used for energy production, Coal, oil and natural gas.

a. Coal:

1. Coal is a solid fossil fuel formed over millions of years by the decay of land vegetation,
2. Coal is a store house of carbon. Coal is found in mines,
3. It is like porous, hard, black rock.
4. It is burnt to obtain heat energy.
5. It is used as a fuel in thermal power plants and to run boilers and railway engines, for cooking and baking bricks.
6. Anthracite is the coal of the highest grade.
7. Producer gas and water gas are obtained from coal.

b. Mineral oil:

1. Mineral oil is the liquid fuel formed by the decomposition of organic substances buried underground,
2. The underground mineral oil is extracted through oil wells.
3. Mineral oil is found mainly in oil sands, shale, sandstone and limestone at a depth of about 1000 to 3000 metres.
4. Mineral oil is also known as petroleum or crude oil. It is greenish-brown in colour.
5. Petroleum is a mixture of many compounds mainly of the hydrocarbon type.
6. It also contains compounds of oxygen, nitrogen and sulphur.
7. Petroleum is extracted through oil wells and refined by fractional distillation to separate other components,
8. Aviation petrol, gasoline, diesel, kerosene, naphtha, lubricating oil, tar are all obtained from petroleum.
9. They are used as fuel and for production of dyes, pesticides, perfumes and artificial fibres.

c. Natural gas:

1. Natural gas is an important fossil fuel.
2. It is lighter than air. It is found with petroleum in underground oil wells and in some places as natural gas alone.
3. The main component of natural gas is methane (CH₄), ethane (C₂H₆), propane (C₃H₈) and butane (C₄H₁₀) are present in small proportions.
4. This gas is highly flammable.
5. This fuel can be carried over long distance by means of a gas pipeline.
6. In absence of pipeline, it is transformed under high pressure into compressed natural gas (CNG) and liquefied natural gas (LNG).

Question b.
Make a list of the components we obtain from mineral oil.
Answer:

1. Mineral oil is the liquid fuel. It is also known as petroleum or crude oil. Petroleum is refined by fractional distillation to separate other components.
2. Aviation petrol, gasoline, diesel, kerosene, naphtha, lubricating oil, tar are the components we obtain from mineral oil.

Question c.
What do we get from forest?
Answer:

1. A forest is a natural habitat of plants, animals and microbes. We get wood, firewood from trees like teak, mahogany, neem, subabhul.
2. Also we get fibers, paper, rubber, gum and aromatic substances.
3. We get many medicinal plants like Adulsa, Bel, Neem, Periwinkle, Cinnamon, Cinchona which are used for treatment of various diseases like cough, cold, diarrhea, fever, cancer, diarrhoea, nausea, malaria.
4. We get fragrant essential oils from lemon grass, vanilla, kewada, khus, eucalyptus.
5. In addition to this we get fruits, bulbs and roots, honey, sealing wax, catechu, dyes from forest.

Question d.
What are the items included in ocean resources? What are their uses?
Answer:

1. Tons of minerals are found in ocean water.
2. They are tin, chromium, phosphates, copper, zinc, iron, lead, manganese, sulphur, uranium etc.
3. We also get many types of gems, conches, shells and pearls from the sea.
4. Mineral oil and natural gas is found at the bottom of sea.

Bio-resources in oceans

• Fishes – like pomfret, seer fish as also shrimps
• prawns – they are sources of proteins and vitamins, therefore, mainly used as sea food
• Dried shrimp, Bombay duck powder – used as poultry feed and is a good manure.
• Shells – used for preparation of medicines, ornaments and decorative articles.
• Fungi – used for the production of antibiotics.
• shark and cod fish – used for producing edible oil rich in Vitamins A, D and E.
• Sea cucumbers – used as medicine for treating cancer and tumours.

Mineral resources from oceans

• Thorium – used in the production of atomic energy.
• Magnesium – used in the flash bulb of a camera.
• Potassium – the main ingredient in production of soap, glass, fertilizer.
• Sodium – used in the production of cloth and paper.
• Sulphate – used in making artificial silk.

Question e.
Why should we prevent the wastage of fuels used for vehicles?
Answer:

1. Vehicles are powered by gasoline or diesel petrol.
2. Nowadays compressed natural gas (CNG) is also used.
3. Aviation petrol, gasoline, diesel, we get from petroleum after fractional distillation.
4. Petroleum is a non-renewable source of energy.
5. It is getting depleted day by day and the demand for fuel has increased greatly due to the rapidly growing population.
6. But the reserves of petroleum (fossil fuel) are limited.
7. It is becoming difficult to meet the increased demand. So we should prevent the wastage of fuel.

Question f.
Why is the diversity of plants and animals in the forests declining?
Answer:

1. The major causes of biodiversity decline are land use changes, pollution, changes in atmosphere, CO₂ concentration, changes in the nitrogen cycle, acid rain, climate alteration and introduction of exotic species.
2. All this is due to population growth.
3. This is the main cause of the loss of biodiversity. More of wood for fuel is been used, more land is required for food production, livestock grazing etc.
4. Rainforest land is converted to industrial and residential usage, so natural habitat of birds, animals is destroyed.
5. Due to population growth most of wild land is converted to crop land. So no space for animals to live, their natural habitat is destroyed.

Question g.
Write the names of five minerals and the useful substances obtained from them.
Answer:
Some important minerals and ores are:

1. Iron ore: It is used for making farming implements, rails of railway tracks etc.
2. Manganese: Compounds of manganese are used in the preparation of medicines and for giving a pink tinge to glass. Manganese is also used in electrical appliances.
3. Bauxite: It contains 55% Aluminium. Therefore, it is used mainly in aeroplanes, transport vehicles and to make electric wire.
4. Copper: It is used to make electric wires as well as in radios, telephones, vehicles, and for making kitchen utensils and statues.
5. Mica: Mica has many uses such as in ayurvedic medicines, dyes, electric machines and equipment, wireless communication equipment, etc.

Question h.
Name the two important stages in the process of obtaining metals from ores.
Answer:
The two important stages in the process of obtaining metals from ores are extraction and purification.

3. What steps are taken for protection and conservation of natural resources?

Question a
What steps are taken for protection and conservation of natural resources?
Answer:

1. Protection and conservation of natural resources is necessary to protect the natural world. (CNRM) Community Natural Resource Management has been promoted in recent years for biological conservation.
2. The World Conservation Union has been formed. It is the world’s leading authority and democratic platform in conservation and sustainability.
3. Young trees should not be cut. More and more trees need to be grown.
4. The stringent restrictions/ laws/ Regulations regarding use of forests should be strictly followed. Awareness is being created through Mass media.

4. Complete the Flow Chart:

Question a.

Answer:

5. How does the economic condition of a nation depend on its natural resources?

Question a.
How does the economic condition of a nation depend on its natural resources?
Answer:
1. Natural resources are a necessary condition for economic growth.
2. Three circles enclosed within one another shows how both economy and society are subsets of our planetary ecological system.

3. Natural resource economics deals with the supply, demand and allocation of the Earth’s natural resources.
4. Economic growth is an increase in the value of goods and services produced in an economy.
5. The natural resources of a country depend on the climatic and environmental conditions.
6. Countries having plenty of natural resources enjoy good growth than countries with small amount of natural resources.
7. A country having skilled and educated work force with rich natural resources takes the economy on the growth path, because skilled and educated people can efficiently utilize or exploit natural resources, e.g. Saudi Arabia: their economic growth is high, because they have oil wells.
8. All countries import fuel or oil from them so Saudi Arabia is economically a rich country.

6. Which medicinal plants will you grow on your school premises and near your house? Why?

Question a.
Which medicinal plants will you grow on your school premises and near your house? Why?
Answer:
1. I will grow tulsi, neem, lemon grass, bel, adulsa, periwinkle, cinnamon, ashwagandha, shatavari, amla, hirda, behda.
2. These plants are used for treatment of various diseases.

• Tulsi → for cough and cold.
• Amla, hirda, behda → Help in digestion of food or any stomach related problems.
• Adulsa → for cough and cold
• Bel → for Diarrhoea
• Neem → Fever and cold
• Periwinkle → Cancer
• Cinnamon → Diarrhoea, nausea.
• Cinchona → Malaria.
• Ashwagandha → It can reduce blood sugar levels. It can reduce stress and anxiety, may reduce symptom of depression.
• Shatavari → has been used for centuries in Ayurveda to support the reproductive system.
• Amla → Excellent source of vitamin C. Amla juice is best tonic to keep you younger for long.
• Hirda → This fruit is commonly called Haritaki. It is used for treating arthritis, dental problems like caries, bleeding gums.
• Behda →(Beleric) is a rejuvenative and laxative, proves beneficial for hair, throat and eyes.
• Tulsi → Tulsi has germicidal, fungicidal, anti-bacterial anti-biotic properties, cures fever. Treats diabetes, protects the heart. Tulsi has anti-oxidant component Eugenol which keeps one’s blood pressure under control.

Project:

Question 1.
Collect conches and shells of various shapes and colours and make a decorative article.

Question 2.
Collect information about the mines of various minerals.

Class 7 Science Chapter 16 Natural Resources Important Questions and Answers

Fill in the blanks:

Question 1.
………….. is the major raw material for biogas.
Answer:
cow dung

Question 2.
Atomic energy is obtained by using ores of ………….. .
Answer:
Uranium

Question 3.
Biogas generation is mainly based on the principle of ………….. .
Answer:
Fermentation

Question 4.
Floods can be prevented by ………….. .
Answer:
Afforestation

Question 5.
Coal, petroleum, natural gas are ………….. resources.
Answer:
non-renewable

Question 6.
The total percent of land of world under forest cover is ………….. .
Answer:
30%

Question 7.
A naturally occurring substance ………….. .
Answer:
minerals

Question 8.
Minerals that contain a high proportion of metal are called ………….. .
Answer:
ore

Question 9.
Coal, mineral oil and natural gas are ………….. .
Answer:
fossil fuel

Question 10.
Deposits of common salt are also found in the earth. This salt is called ………….. .
Answer:
rock salt

Question 11.
………….. is the liquid fuel formed by the decomposition of organic substances.
Answer:
Mineral oil

Question 12.
The underground mineral oil is extracted through ………….. .
Answer:
oil wells

Question 13.
Mineral oil is also known as ………….. or ………….. .
Answer:
petroleum, crude oil

Question 14.
………….. are the preserved remains of dead organisms in rock.
Answer:
Fossil

Question 15.
Coal can be formed from ………….. .
Answer:
Fossils

Question 16.
Impurities of sand and soil in ore are called ………….. .
Answer:
Gangue

Question 17.
Coal mainly contains ………….. .
Answer:
carbon

Question 18.
Petroleum is formed from ………….. .
Answer:
organisms in sea

Question 19.
Separation of various fractions of petroleum is called ………….. .
Answer:
Refining

Question 20.
We can obtain minerals from rocks by ………….. .
Answer:
mining

Question 21.
………….. is the most important ore of aluminium
Answer:
Bauxite

Question 22.
………….. is the coal of the highest grade.
Answer:
Anthracite

Question 23.
Metals are obtained from their ore by ………….. and ………….. .
Answer:
extraction, purification

Question 24.
………….. is the largest oil and gas research and production company in India.
Answer:
ONGC

Question 25.
Natural gas is transformed under high pressure into ………….. and ………….. .
Answer:
LNG and CNG

Question 26.
The main component of Natural gas is ………….. .
Answer:
Methane

Question 27.
………….. and ………….. are used for adding fragrance in soaps and incense sticks.
Answer:
Sandalwood and oil of Encalyptus

Question 28.
………….. is a natural herbal medicine for cough and cold.
Answer:
Adulsa

Answer the following:

Question 1.
What is meant by natural resources?
Answer:

1. We get many substances from nature.
2. They satisfy a variety of our daily needs. Soil, stones, minerals, air, water, plants and animals on the earth are all various kinds of natural resources.

Question 2.
What are alternative fuels?
Answer:
Hydrogen, biofuels, methanol or wood alcohol, ethanol or green alcohol are some of the alternative fuels.

Question 3.
What is meant by fuels?
Answer:

1. Fuel is a substance that is used in day-to-day life and burned to generate energy.
2. Fuels such as coal, wood, oil, gas provide energy when burned.
3. Fuels are found in solid, liquid or gaseous state.

Question 4.
Which natural resources do we use as fuels?
Answer:
We use coal, mineral oil and natural gas as fuels.

Question 5.
What is meant by forests?
Answer:
An extensive area of land covered by a variety of plants is called a forest. A forest is a natural habitat of plants, animals and microbes.

Question 6.
What are the uses of forests?
OR
Write short note on forest and its uses.
Answer:

1. A forest is a natural habitat of plants, animals and microbes.
2. Forest help improve and maintain the quality of environment.
3. Forest helps in prevention of soil-erosion, help to control floods, protects wild life, maintains the balance of atmospheric gases.
4. We get many medicinal plants from forest which help in treatment of various diseases.
5. Examples Adulsa, Bel, Neem, periwinkle, amla tulsi, cinnamon.
6. We also get wood, firewood from trees like teak, mahogani, neem, sababhul. Wood is useful for making furniture, farming implements, in construction work.
7. Forest wealth includes fibres, paper, rubber, gum and aromatic substances.
8. We get fragrant essential oils from lemon grass, vanilla, kewada and eucalyptus.
9. They are used for making soaps, cosmetics and incense sticks. We get various fruits, bulbs, roots, honey, sealing wax, catechu dyes etc. from forest.

Question 7.
Are minerals to be found in seas and on the seabed as they are found inside the earth?
Answer:
Yes, there are very large reserves of tin chromium, phosphates, copper, zinc, iron, lead, manganese, sulphur, uranium etc. in the ocean and seabed.

Question 8.
How is mineral oil formed?
Answer:

1. Mineral oil is the liquid fuel formed by the decomposition of organic substances buried underground.
2. Millions of years ago, bodies of dead sea organisms sank to the bottom of the sea.
3. Layers of soil and sand collected on them.
4. Due to high pressure and temperature the remains of the dead organisms were transformed into mineral oil.
5. The underground mineral oil is extracted through oil wells.

Use your brain power!

Question 1.
Why are all minerals not ores?
Answer:

1. Minerals that contain a high proportion of metal are called ores.
2. Majority of the metals occur in the form of compounds called ores.
3. But all minerals are not ores.
4. Few metals like gold, silver, copper, platinum and bismuth occur in free state in nature. So all minerals are not ores.

Question 2.
What is meant by metal mineral and non¬metal mineral?
Answer:

1. Metal-minerals contain metallic elements in their chemical formula. So they are called metal-minerals, for example, iron, copper, gold, silver etc.
2. They contain metal in raw form.
3. Non-metallic minerals do not contain metal elements in their inorganic chemical formula Example, Clay, Diamond, Dolomite, Gypsum, Mica, Quartz.

Question 3.
Why is mineral oil called ‘liquid gold’?
Answer:
Because of its high price and value and its economic need, the mineral oil is called liquid gold. It’s reserve is less and demand is more.

Question 4.
Why is coal called black gold?
Answer:

1. Coal is a storehouse of carbon. Coal is used as a fuel, in thermal power plants as well as to run boilers and railway engines.
2. It is used as a fuel for cooking and for baking bricks in kilns on a large scale.
3. The gaseous fuels, producer gas and water gas are obtained from coal.
4. Coal as an energy resource, contributes greatly to industrial development.
5. As coal is black in colour and worth a lot of money just like gold, it is called black gold.

Question 5.
What would happen if underground mineral resources are exhausted?
Answer:

1. Coal, petroleum and other mineral are all non-renewable sources of energy.
2. The reserve is less and demand is more. They would get exhausted one day.
3. If such a situation occurs, we will not get electricity.
4. All our household and industries depend on electricity.
5. Transportation and household items, and food items would become very costly.
6. The survival of human life will be ver\ difficult.

Question 6.
Why is natural gas an eco-friendly fuel?
Answer:

1. Natural gas is an important source of energy which is eco-friendly because of its low carbon dioxide emission.
2. When burned it produces 45% less CO₂ than coal, 30% less than oil, and about 15% less than wood.
3. It does not produce carbon monoxide, sulphur dioxide or airborne particles, all of which are harmful to human and animal health.
4. It is referred as the clean energy source and is fuel for the present century as it does not ‘ pollute the atmosphere or contribute to global warming.

Question 7.
What useful things will we have to do without if rubber is no longer available?
Answer:

1. Rubber has played a largely hidden role in global environment history for more than 150 years.
2. In industries, rubber is needed to connect and protect all moving parts of machines.
3. Native people used rubber for rubber boots.
4. Household uses rubber in everything viz dish washing gloves, toys, jar seals, tyres in vehicles.
5. Welcome mat at the door, Boots, raincoats, mattress cushions, earplugs, hot water bottles, surgical tubing and gloves, in labs, birth control device.
6. In schools rubber bands, erasers, mouse pads, key board, rolling chair wheels. Head phone pads, rubber stamps are useful items used in schools and offices.

Question 8.
What are the adverse effects of clearing of forest or cutting down trees?
Answer:

1. Clearing of forest is also called Deforestation.
2. Removal or cutting down of trees has resulted in damage to habitat, biodiversity loss and aridity.
3. If has adverse impacts on concentration of atmospheric carbon dioxide. (Trees use up carbon dioxide from the atmosphere for the process of photosynthesis.)
4. Deforestation is a main contributor to global warming. Major cause of enhanced greenhouse effect. Deforestation cause carbon dioxide to linger in the atmosphere.
5. Deforestation reduced the content of water in the soil and ground water and atmospheric moisture, because trees extract ground water through the roots and release it into the atmosphere.
6. When a part of forest is removed the trees no longer transpire this water, resulting in much drier climate.
7. Due to deforestation soil erosion and flooding, landslide problems occur.
8. Deforestation results in decline in biodiversity, on a natural global scale is known to cause the extinction of many species.
9. Forest is habitat for wild life, and many medicinal plants. If forests are removed it will affect wild life and also we will not get medicinal plants.

Find out:

Question 1.
How did the various ages of the prehistoric period get their names on the basis of the uses of metals.
Answer:
1. The three-age system in history archaeology, and physical anthropology is a methodological concept adopted during the 19th century by which artifacts and events of late prehistory and early history could be ordered into a recognizable chronology.

2. Initially developed by C. J. Thomson, director of the Royal Museum of Nordic Antiquities, Copenhagen – as a means to classify the museum’s collection according to whether the artifacts were made of stone, bronze or iron.

3. Depending-upon the use of stone, bronze, iron, that period was known as stone age, bronze age, and iron age, respectively.

Answer the following:

Question 1.
Write down the difference between Metal minerals and Non-metallic minerals.
Answer:

Metal minerals	Non-metallic minerals
1. Metal minerals contain metal in raw form.	1. Non-metallic minerals do not contain metal.
2. These metals are generally associated with igenous rocks.	2. These metals are generally associated with sedimentary rocks.
3. They are usually hard and have shine of their own.	3. They are not usually hard, have no shine of their own.
4. e.g. Iron, copper tine, bauxite.	4. e.g. Salt, coal, mica, clay.

Question 2.
Write down the different types of coal.
Answer:
Peat, lignite (brown coal), bituminous coal and anthracite are various types of coal.
Anthracite is the coal of the highest grade.

Question 3.
Write down the characteristics of Compressed Natural Gas.
Answer:
Characteristics of CNG:

1. Catches fire easily.
2. No solid waste remains after combustion.
3. Carbon dioxide and water are formed in small quantities.
4. Other pollutants are not produced.
5. Can be transported easily.
6. Combustion can be controlled easily.

Observe the pictures and answer the question.

Question a.
What is the process shown in the given picture?
Answer:
The process shown is formation of mineral oil and natural gas.

Question b.
Explain the process.
Answer:

1. Mineral oil is the liquid fuel formed by the decomposition of organic substances buried underground.
2. Millions of years ago, bodies of dead sea organisms sank to the bottom of the sea.
3. Layers of soil and sand collected on them.
4. Due to high pressure and temperature the remains of the dead organisms were transformed into mineral oil.
5. The underground mineral oil is extracted through oil wells.

Question c.
What are the gaseous substances formed in the above process?
Answer:
Natural gas is also formed along with mineral oil. It contains methane, ethane, propane and butane gases.

Question d.
When the products of the process is refined, what other components are produced?
Answer:
When mineral oil is refined by fractional distillation products produced are petrol, diesel, kerosene, naphtha lubricating oil, tar, etc.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 15 Materials We Use Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 15 Materials We Use

Class 7 Science Chapter 15 Materials We Use Textbook Questions and Answers

1. Fill appropriate terms in the blanks:
(white cement, soap, detergent, wearing of bones, tooth decay, hard, soft, portiand, fatty acid)

Question a.
The substance that helps water to remove dirt from the surface of material is called …………… .
Answer:
soap

Question b.
Fluoride is used in toothpaste to prevent …………… .
Answer:
tooth decay

Question c.
Soap is a salt of …………… and sodium hydroxide.
Answer:
fatty acid

Question d.
Synthetic detergents can be used in …………… water as well.
Answer:
hard

Question e.
For construction purposes …………… Cement is the most commonly used cement.
Answer:
white cement

2. Write answers to the following questions. 

Question a.
How does the use of a detergent help to clean soiled clothes?
Answer:

1. A molecule of a detergent holds on to a water molecule at one end and an oil molecule at the other.
2. As a result the molecules of oil mix with the water.
3. This is how detergent acts on our soiled clothes. So detergent removes any oil or dirt sticking on to our clothes.
4. Due to the property of holding on to both oil and water, soap water spreads easily on many types of surfaces.
5. This property of spreading on a surface is called surface activity.
6. Detergents are surface active.
7. One effect of surface activity is lather formation.

Question b.
How will you check with the help of soap powder whether water is hard?
Answer:

1. In the hard water, (of a well or a tube-well), soap does not give lather but forms a scum.
2. As a result, soap loses its cleansing property. So with help of soap we will come to know that it is a hard water.

Question c.
What are the important ingredients of a tooth paste and what is the function of each?
Answer:

1. The important ingredients of a toothpaste are calcium carbonate and calcium hydrogen phosphate.
2. They remove the dirt on teeth. These ingredients also polish the teeth.
3. A certain proportion of fluoride in the tooth paste helps prevent tooth decay.
4. It is essential for the enamel covering of teeth.

Question d.
What are the ingredients of cement?
Answer:

1. Cement is a dry, greenish grey powder with fine particles.
2. It is made from silica (sand), alumina (aluminium oxide), lime, iron oxide and magnesia (magnesium oxide).

Question e.
What will happen if cement is not used in making concrete?
Answer:

1. In making concrete strong, the ingredients cement, water, sand and gravel should usually be mixed in the ratio of 1 : 2 : 3 : 0.5 to achieve maximum strength.
2. If enough cement is not used then the concrete will eventually fall apart, as cement is used as a binding agent.

Question f.
Make a list of detergents, that you use. Answer: There are two types of detergents that we use, (a) Natural (b) Man-made detergents.

1. Natural detergents are soap nut (ritha) soap pod (shikekai).
2. Man-made detergents are soap, hard soaps, soft soaps.
3. Synthetic detergents have taken the place of soap.
   • Detergents are commonly available as powders or concentrated solution.
   • Detergents are for laundry, washing clothes and cleaning dishes.
4. Alkaline detergents used for hard surface cleaning.

Question g.
What should be expected from a detergent for delicate garments?
Answer:

1. Detergents should not be strong, they may spoil the texture, colour of delicate garments.
2. Now a days many detergents are available especially for woollen, delicate clothes.
3. They should not contain bleach, phosphorous which will harm delicate clothes.

Question h.
What is meant by surface activity? Name three chemicals responsible for the surface activity of various detergents.
Answer:

1. Due to the property of holding on to both oil and water, soap water spreads easily on many types of surfaces.
2. The property of a substance of spreading on a surface is called surface activity and the substance is called surfactant.
3. Detergents are surface active.
4. They increase the spreading and wetting ability of water by reducing its surface tension.
5. Chemicals responsible for the surface activity of various detergents is phenol, Aprotinin.

3. What are the similarities and differences between:

Question a.
Natural detergents and Man-made detergents
Answer:

Natural detergents	Man-made detergents
1. Soap nut (ritha) and soap pod (shikekai) are the natural detergents.	1. Soap is man-made detergent soft soap and hard soap.
2. Natural detergents do not have harmful effect on human skin or on silk or woollen clothes.	2. Soap has effect on skin and cloth because it has chemicals in it.
3. Soap nut, soap pod contain a chemical saponin.	3. Soap has acid in it, soap is sodium and potassium salt of fatty acids.
4. It is naturally available.	4. It is man made using chemicals and oil.

Question b.
Soap and Synthetic detergents
Answer:

Soap	Synthetic detergents
1. Soap is man-made detergent, it is in use since ancient times.	1. Synthetic detergent have taken the place of soap.
2. Soap loses its cleansing property in hard water it does not give lather.	2. Synthetic detergent can be used in hard water also.
3. Soap was prepared by using animal fat and wood ash.	3. Synthetic detergent are obtained by subjecting fats, kerosene to various chemical processes.
4. Variety of soaps are available, soft soap for bathing, hard soap for washing, cleaning.	4. Variety of synthetic detergents are available – Ariel, Surf Excel, etc.

Question c.
Bath soap and Soap for washing clothes
Answer:

Bath soap	Soap for washing clothes
1. Soft soap is used for bathing.	1. Hard soap is used for washing clothes.
2. Soft soap is potassium salt is fatty acids.	2. Hard soap is sodium salt of fatty acid.
3. Soft soap dissolves more easily readily in water.	3. Hard soap do not dissolve easily in water.
4. Now a days many perfumes, moisturizes are mixed to make it more attractive and useful.	4. In this type of soap now a days germicides, anti foaming agents are mixed to make it more useful.

Question d.
Modern cement and Ancient cement
Answer:

Modem cement	Ancient cement
1. Cement manufactured from 60% lime, silica 25% and alumina 5%. the rest is iron oxide and gypsum.	1. Romans used to make aqueous cement by mixing volcanic ash in moistened lime. It was very durable.
2. It is the most commonly used cement for Construction work.	2. It is Roman cement volcanic ash prevent cracks from spreading.
3. It is called Portland Cement.	3. It is called Aqueous Cement.

4. Explain why –

Question a.
Soap cannot be used in hard water.
Answer:

1. In the hard water of a well or a tube well, soap does not give lather but forms a scum.
2. As a result soap loses its cleansing property. So soap cannot be used in hard water.

Question b.
Oil does not mix in water. However, oil and water become homogenous if a sufficient quantity of detergent is added.
Answer:

1. A molecule of a detergent holds on to a water molecule at one end and an oil molecule at the other.
2. As a result the molecules of oil mix with the water, and we will see that the water and oil have become homogenous and the colour of the mixture appears milky.

Question c.
Synthetic detergents are superior to soap.
Answer:

1. Soap is a man-made detergent which has been in use since ancient times.
2. It was prepared by using animal fat and wood ash. In hard water, soap does not give lather, it loses its cleansing property.
3. So we can not use soap in hard water. Now synthetic detergents have taken the place of soap.
4. They can be used in hard water as well
5. Synthetic detergents have many more advanced properties like they are added with perfumes, conditioner for fabric, etc.

Question d.
Often coloured spots are formed on clothes during washing.
Answer:

1. Curry stains stick fast to the criss-crossing threads of the material of our clothes.
2. Curry contains turmeric a natural indicator which turns red in a basic solution.
3. Soaps are sodium salts of fatty acids and are basic in nature.
4. While washing the clothes, turmeric reacts with soap solution and turns red forming red spots on the clothes.
5. But the spots disappear after washing the clothes with plenty of water.

Question e.
Tobacco masheri should not be used for cleaning teeth.
Answer:

1. Masheri is the smokeless form of tobacco. It is tobacco, containing teeth cleaning powder
2. It contains tobacco leaves.
3. Tobacco contains toxic and Carcinogenic chemicals which can cause cancer, oral cancer, mouth and throat cancer, gum disease, tooth decay.
4. Its use can cause abnormal delivery in pregnant women.

Project:

Question 1.
Visit a cement factory. See how cement is prepared and discuss the process.

Question 2.
Write a conversation based on cement houses, mud-houses and wattle-and-daub houses.

Class 7 Science Chapter 15 Materials We Use Important Questions and Answers

Fill in the blanks:

Question 1.
The principal ingredients of a toothpaste are ………………. and ………………. which remove the dirt on the teeth.
Answer:
Calcium carbonate, calcium hydrogen phosphate

Question 2.
………………. in the toothpaste helps prevent tooth decay.
Answer:
Fluoride

Question 3.
The property of a substance of spreading on a surface is called ………………. .
Answer:
surface activity

Question 4.
………………. and ………………. are the natural detergent in common use.
Answer:
Soap nut, Soap pod

Question 5.
Soap nut and soap pod contain a chemical named ………………. .
Answer:
Saponin

Question 6.
………………. is a man-made detergent.
Answer:
Soap

Question 7.
………………. is used for washing clothes.
Answer:
Hard soap

Question 8.
………………. is used for bathing.
Answer:
Soft soap

Question 9.
Hard soap is ………………. salt of fatty acids.
Answer:
Sodium

Question 10.
Soft soap is ………………. salt of fatty acids.
Answer:
Potassium

Name the following:

Question 1.
A substance which is spread on a given surface and used for cleaning.
Answer:
Surfactant

Question 2.
A chemical contained in soap nut and pod.
Answer:
Saponin

Question 3.
An element which helps prevent tooth decay which is used in toothpastes.
Answer:
Fluoride

Question 4.
The latin word which means detergent.
Answer:
Detergere

Question 5.
A cement used for construction purpose.
Answer:
Portland cement

Question 6.
A mixture of cement, water, sand and gravel.
Answer:
Concrete

Question 7.
A natural detergent.
Answer:
Soap nut

Choose the correct option:

Question 1.
Which one of these material grows on an animal
(cotton, rubber, wood, wool)
Answer:
Wool

Question 2.
Which of these is man-made?
(oranges, apples, plastic bags, tomatoes)
Answer:
Plastic bags

Question 3.
The statue is made from marble, marble is a ………….. material.
(weak, elastic, man-made, natural)
Answer:
Natural

Question 4.
Toy Duck is made from plastic. Plastic is a ………….. material.
(natural, man-made, raw, precious)
Answer:
Man-made

Question 5.
Which of these materials is natural?
(Nylon, Rock, Plastic, Polythene)
Answer:
Rock

Question 6.
Which one of these is a natural material?
(Lemonade, Cola, Water, Ice cream)
Answer:
Water

Question 7.
The toy plane made from wood. Wood is a ………….. material.
(man-made, natural, weak)
Answer:
Natural

Question 8.
Which one of these materials is natural?
(Nylon, cotton, polythene, polyesters)
Answer:
Cotton

Match the following:

Question 1.

Column ’A’	Column ’B’
1. Fluoride	a. Man-made detergent
2. Soap nut	b. Sodium salt of fatty acid
3. Soap	c. Man-made material
4. Cotton	d. Prevents tooth decay
5. Nylon	e. Potassium salt of fatty acid.
6. Hard soap	f. Natural detergent
7. Calcium carbonate	g. Natural material
8. Soft soap	h. Main ingredients of toothpaste

Answer:

Column ’A’	Column ’B’
1. Fluoride	d. Prevents tooth decay
2. Soap nut	f. Natural detergent
3. Soap	a. Man-made detergent
4. Cotton	g. Natural material
5. Nylon	c. Man-made material
6. Hard soap	b. Sodium salt of fatty acid
7. Calcium carbonate	h. Main ingredients of toothpaste
8. Soft soap	e. Potassium salt of fatty acid.

Find out:

Answer the following questions:

Question 1.
What is the source of the fluoride in a tooth paste or tooth powder?
Answer:
A naturally occurring mineral found in tooth paste and drinking water. Sodium Fluoride (NaF) is the source of fluoride in toothpaste.

Question 2.
Note down all the information given on a tooth powder/toothpaste container or carton and discuss.
Answer:
1. The carton shows the name of the company and name of toothpaste and its contains all the ingredients present in toothpaste.

2. Licence No. of company, Regd. Trade Mark of Colgate Palmolive Co-manufactured by Colgate-Palmolive (India) Ltd. Licenced user of Trade Mark made in India. Tooth paste contains 1000 ppm max of available fluoride when packed.

3. Ingredients: Calcium carbonate, sorbitol, sodium lauryl sulphate, silica, sodium silicate flavour, sodium monoflouro phosphate, sodium bicarbonate, benzyl alcohol.

4. Direction for use: Brush thoroughly atleast twice a day.
5. Children under 6 years of age should have adult supervision and use only appropriate amount.

Question 3.
Now a days why are the roads made of concrete?
Answer:

1. Concrete is prepared by mixing cement, limestone, sand, gravel, and water. It is solid, more durable and strong.
2. There is no erosion for many years and roads are smoother. So the roads are made of concrete.

Question 4.
What causes the hardness of water?
Answer:

1. Hardness is a measure of amount of dissolved salts in water.
2. It is caused by dissolved salts like carbonates, chlorides mostly of calcium and magnesium
3. Presence of these makes washing of clothes by soap difficult.
4. Hard water is water that has high mineral content.
5. Hard water is formed when water percolates through deposits of limestone and chalk.

Can you tell?

Answer the following questions:

Question 1.
Which substances were used earlier for cleaning teeth?
Answer:
In olden times neem twigs, coal powder ash, tooth powder, salt, pomegranate rind, were used for cleaning teeth.

Question 2.
What do we use today to clean our teeth?
Answer:
Now a days we use variety of toothpastes and tooth powders to clean our teeth.

Question 3.
What do we use for cleansing our body?
Answer:
Soap, many liquid body wash are also used to clean our body.

Question 4.
What are the materials used for construction?
Answer:
Metals, wood, stone, cement, concrete, timber, bricks, metal sheet, soil, Earth, marble, aluminium, iron, steel, bamboo, glass, plastic.
Concrete: is a wet mixture of sand, gravel, cement, and water used to create building foundations, footpaths or roads.

Question 5.
Which of the houses seen in the pictures here have a strong structure? Why?

Answer:
The houses made from stone, bricks, and cement and concrete have a strong structure.

Write short notes on or Explain:

Question 1.
Natural detergent
Answer:

1. It is naturally available soap nut (ritha) and soap pod (shikekai) are the natural detergents in common use.
2. They contain a chemical named saponin.
3. Soap nut and soap pod do not have any harmful effect on human skin or on silk, woollen threads, and cloth.

Question 2.
Man-made detergents
Answer:

1. Detergent which is made by processing naturally available material, soap is a man-made detergent which has been in use since ancient times.
2. In those days soap was prepared by using animal fat and wood ash.
3. Therefore two types of soap (a) Hard Soap is used for washing clothes. It is a sodium salt of fatty acids, (b) Softsoap is used for bathing. It is a potassium salt of fatty acids.
4. It does not cause irritation of the skin.
5. But we can’t use soap in hard water because soap does not give lather but forms a scum. So, soap loses its cleansing property so now synthetic detergent have taken the place of soap.
6. Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes. These can be used in hard water as well.

Question 3.
Soap
Answer:
Two types of soap are:
1. Hard soap is used for washing clothes. It is a sodium salt of fatty acids.
2. (a) Softsoap is used for bathing. It is a potassium salt of fatty acids, (b) It does not cause irritation of the skin, (c) But we can’t use soap in hard water because soap does not give lather but forms a scum, (d) So, soap loses its cleansing property so now synthetic detergents have taken place of soap, (e) Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes, (f) These can be used in hard water as well.

Question 4.
Concrete
Answer:

1. Concrete is prepared by mixing cement, water, sand and gravel.
2. For making a strong and leak proof slab certain substances are mixed in concrete.
3. Now a days, roads are made of concrete because they are very durable, strong and smooth.

Question 5.
Surface activity
Answer:

1. Soap molecule has the property of holding on to both oil and water soap water spreads easily on many types of surfaces.
2. The property of a substance of spreading on a surface is called surface activity and the substance is said to be a surfactant.
3. Detergents are surface-active. One effect of surface activity is lather formation.

Question 6.
Explain the method of preparation of soap.
Answer:
Material required for preparation soap are 15 g sodium hydroxide, 60 ml coconut oil, 15 g salt, perfume, a glass rod, beaker, tripod, wire gauze, burner, water mould etc.
Procedure:

1. Take 60 ml of coconut oil in a beaker.
2. Dissolve 15 g sodium hydroxide in 50 ml water. Mix the sodium hydroxide solution in the oil slowly, while stirring with a glass rod.
3. Heat the mixture, and boil it for 10 – 12 minutes, stirring it all the while.
4. Take care that the mixture does not boil over while heating.
5. Dissolve 15 g salt in 200 ml water, pour this solution into the above mixture and stir.
6. The soap formed by the chemical reaction now floats on the water. After some time, it becomes thick.
7. Now separate the thick soap and add the perfume to it, shape the bar of soap using the mould.
8. In this process, fat and alkali combine to form salts of fatty acids.
9. Chemically, soap is a sodium or potassium salt 4 of fatty acids.

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 14 Elements, Compounds and Mixtures Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 14 Elements, Compounds and Mixtures

Class 7 Science Chapter 14 Elements, Compounds and Mixtures Textbook Questions and Answers

1. Who are my companions?

Question a.

Column ‘A’	Column B’
1. Stainless steel	a. Non-metal
2. Silver	b. Compound
3. Bhajani mixture for milling	c. Mixture
4. Salt	d. Element
5. Coal	e. Alloy
6. Hydrogen	f. Metal

Answer:

Column ‘A’	Column B’
1. Stainless steel	e. Alloy
2. Silver	f. Metal
3. Bhajani mixture for milling	c. Mixture
4. Salt	b. Compound
5. Coal	a. Non-metal
6. Hydrogen	d. Element

2. Write the names of elements from the following symbols:
Zn, Cd, Xe, Br, Ti, Cu, Fe, Si, Ir, Pt.

Question a.
Write the names of elements from the following symbols:
Zn, Cd, Xe, Br, Ti, Cu, Fe, Si, Ir, Pt.
Answer:

Symbol	Element
Zn	Zinc
Cd	Cadmium
Xe	Xenon
Br	Bromine
Ti	Titanium
Cu	Copper
Fe	Iron
Si	Silicon
Ir	Iridium
Pt	Platinum

3. What are the molecular formulae of the following compounds?
(Hydrochloric acid, Sulphuric acid, Sodium chloride, Glucose, Methane)

Question a.
What are the molecular formulae of the following compounds?
(Hydrochloric acid, Sulphuric acid, Sodium chloride, Glucose, Methane)
Answer:

• Hydrochloric acid → HCl
• Sulphuric acid → H₂SO₄
• Sodium Chloride → NaCl
• Glucose → C₆H₁₂O₆
• Methane → CH₄
• Water → H₂O
• Carbon dioxide → CO₂
• Sucrose (sugar) → C₁₂H₂₂O₁₁

4. Give scientific reasons:

Question a.
Buttermilk is churned to get butter.
Answer:

1. Churning is the process of shaking up buttermilk to make butter.
2. Butter is essentially the fat of milk.
3. Churning physically agitates the cream until it ruptures the membrane surrounding milk fat
4. Fat droplets can join with each other to form clumps of fat.

Question b.
In Chromatography the ingredients of a mixture rise up to a limited height when water rises up to the upper end of the paper.
Answer:
In Chromatography two properties of substances are used, (a) They are the stability of the substances in the solvent that moves up. The ability of the substance to stick to the stationary filter paper, (b) So all the components of the mixture do not rise all the way to the upper end of the filter paper but remain behind at limited heights.

Question c.
A wet cloth is wrapped around a water storage container in summer.
Answer:
A wet cloth will absorb the heat from the surroundings and it will keep the water in the container, cool for a longer time.

5. Explain the difference.

Question a.
Metals and Non-metals
Answer:

Metals	Non-metals
1. Metals are good conductors of heat and electricity.	1. Non-metals are poor conductors of heat and electricity.
2. Metals are solids at room temperature except for mercury.	2. Non-metals exists in all three states.
3. Metals are lustrous, (shiny)	3. Non-metals are not lustrous, (dull appearance) except graphite.
4. Metals are malleable (can be hammered into sheets)	4. Non-metals are brittle, not malleable.
5. Metals are ductile, can be drawn into wire.	5. Non-metals are not ductile.
6. Metals are very hard and strong.	6. Non-metals are brittle, will break down into pieces except diamond.

Question b.
Mixture and Compound
Answer:

Mixture	Compound
1. The different substances are not chemically joined together to form a mixture but mixed physically.	1. A compound is formed when two or more elements chemically combine together e.g. H2O → chemical formula of water.
2. Each substance in the mixture retains its own properties	2. Compound has fixed properties.
3. Mixtures are impure substances.	3. Compounds are pure substances.
4. Substances from the mixture can easily be separated by physical methods.	4. The constituents of a compound can be separated only by chemical methods.
5. The constituents of a mixture are present in varying proportions.	5. The constituents of a compound are present in fixed proportion.

Question c.
Atoms and Molecules
Answer:

Atoms	Molecules
1. An atom is the fundamental part of matter.	1. A molecule is a group of chemically bonded atoms.
2. Atoms are basic building blocks of matter.	2. Molecule is the smallest unit of a chemical compound
3. It is foundation of molecules.	3. It is foundation of chemical compound.

Question d.
Separation by distillation and Separation by separating funnel
Answer:

Separation by distillation	Separation by separating funnel
1. Distillation is used for purification of impure liquids, for separating liquid and solids (Separation of mixture containing two miscible liquids) e.g. to separate salt and water from saltwater.	1. This procedure is used for separating two liquids e.g. separating oil and water, (two immiscible liquids)

6. Write answers to the following questions in your own words.

Question a.
How are the components of mixture separated by simple methods?
Answer:
1. Component of mixtures are separated by straining, filtering, sifting, picking, sorting, winnowing, combing with a magnet and sublimation.
2. In a mixture, the constituent substances do not lose their identity, they can be separated easily by physical methods.
a. Sedimentation: (i) It is a process of separating an insoluble solid from a liquid in which it is suspended, by allowing it to settle to the bottom of the container, e.g. Muddy water contains heavier particles like sand and soil, (ii) Leave this muddy water undisturbed for some time, (iii) The heavier soil and sand particles settle down and the clear upper water is poured out by decantation.

b. Filtration: It is used for separating insoluble solids from a liquid, e.g. mixture of chalk and water is poured through a filter paper in a funnel while the water gets

collected in the beaker below, chalk is retained in the filter paper.

c. Evaporation: It is used for recovering dissolved solid substances from solutions by evaporation e.g. sugar can be recovered from sugar-water.

d. Distillation: It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back. e.g. A mixture of common salt and water is taken in distillation flask and heated. Steam rises up and comes out into condenser.

e. Sublimation: It is a process in which some solids on heating are transformed directly to vapour without passing through the liquid state, (i) It is used to separate a mixture of solids. The vapours are cooled separately, (ii) Used to separate ammonium chloride, iodine, camphor and sulphur from any mixture.

f. Magnetic separation: A mixture with iron fillings as one of the components can be separated using magnet to attract the iron particles away from the mixture.

Question b.
Which elements (metals, non-metals) compounds and mixtures do we use in our day to day life?
Answer:
Elements – non-metal

• Oxygen, nitrogen → present in air
• Hydrogen → present in water
• Silicon → in memory card
• Lithium → to make batteries
• Neon → in neon signs/lights
• Sulphur → used in water treatment, agricultural pesticides

Elements – metals

• Calcium → in milk
• Silver, gold → used in jewellery
• Aluminium, copper, iron → Kitchen vessels
• Mercury → in thermometer
• Copper → electric wires

Compounds:

• Sodium chloride → table salt
• Sodium carbonate → washing soda
• Sodium bicarbonate → baking soda
• Sodium hypochloride → bleaching powder
• Sodium hydroxide, Potassium hydroxide → in making soaps
• Calcium oxide, Calcium hydroxide → in white washing the buildings.
• Hydrochloric acid → in cleaning toilets
• Sucrose → sugar used in cooking and baking.

Mixtures:

• Bhel → mixture of puffed rice, sev, groundnuts, lemon juice
• Concrete → mixture of cement, sand and rocks
• Salad → mixture of onion, cucumber, tomato, lettuce, etc.
  Sherbet and saltwater are also mixtures.

Question c.
In everyday life, where and for what purpose do we use centrifugation?
Answer:
Centrifugation: It is a process which involves application of centrifugal force.
1. It is used in industrial and laboratory settings. It is used for separation of fluids, gas or liquid based on density. In centrifugation mixture is separated through spinning and the solid settles to the bottom and the solution is clear.

2. Best example of centrifugal force is working of washing machine when it dries the clothes. The wet clothes are moving in circular path and a force acts on water particles in clothes and this force pulls water all outer side. Force involved is centrifugal force which removes the water from the clothes and clothes are dried in this way.

3. Cream separation: When the machine moves, the rod set inside milk moves and milk is pressurised and solid part from this milk goes outside due to centrifugal force and this solid part is cream. In this way the cream is separated from the milk.

Question d.
Where are methods of separation by distillation and by separating funnel used?
Answer:
1. Distillation: It is the process of separating the components or substances from a compound. It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back.
Distillation method is used in the following:

• to separate components of air into oxygen, nitrogen, argon, etc.
• to separate salt from saltwater.
• to purify impure liquids.
• to prepare distilled water.

2. Separating funnel: When a mixture of two immiscible liquids is left undisturbed, two layers are clearly seen to have formed, (a) The heavier of the liquids remain below and the lighter liquid floats on it. (b) So two liquids in a mixture can be separated by making use of this property, e.g.

• to separate kerosene and water.
• to separate oil and water.

Question e.
Which precaution will you take while using the methods of distillation and separation by separating funnel?
Answer:
In using distillation:

1. Allow sufficient space to work in, working area should be well lit and well ventilated to prevent the accumulation of alcoholic vapours.
2. Keep a fire extinguisher handy.
3. There should be no obstruction in the piping that could cause pressure build-up in the stills and cause it to burst.

In using separating funnel:

1. Stopper should be tightly fitted so that the solution does not leak out when the separating funnel is inverted.
2. Never throw any layer away until you are absolutely sure that you isolated the final product.

Project:

Question a.
Visit a jaggery or a sugar factory. Obtain information about the methods that are used to separate the components of the mixture while making jaggery or sugar. Present it in the class.

Class 7 Science Chapter 14 Elements, Compounds and Mixtures Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
………………, ……………….. and are three states of matter.
Answer:
Solid, liquid, gaseous

Question 2.
Molecules in ……………….. phase of matter are tightly packed together.
Answer:
solid

Question 3.
A ……………….. has a definite volume, but not a definite shape, it takes the shape of its container.
Answer:
liquid

Question 4.
The temperature at which a liquid becomes a solid is called ……………….. .
Answer:
freezing point

Question 5.
Anything that takes up space and has mass is called ……………….. .
Answer:
matter

Question 6.
A ……………….. has no definite shape and no definite volume.
Answer:
Gas

Question 7.
The amount of space that matter occupies is called ……………….. .
Answer:
volume

Question 8.
A ……………….. has a definite shape and definite volume.
Answer:
solid

Question 9.
When a liquid is heated it will ……………….. .
Answer:
expand

Question 10.
A ……………….. is formed by mixing different elements or compounds.
Answer:
mixture

Question 11.
The substance formed by a chemical combination of two or more elements is called a ……………….. .
Answer:
compound

Question 12.
The elements that show some properties of metals and non-metals are called ……………….. .
Answer:
metalloids

Question 13.
Elements are generally classified into ……………….. and ……………….. .
Answer:
metal, non-metals

Question 14.
The smallest particles of substances are called ……………….. .
Answer:
molecules

Question 15.
To date, scientists have discovered ……………….. elements and of these ……………….. elements occur in nature.
Answer:
118, 92

Question 16.
……………….. was the first scientist to use symbols for elements.
Answer:
Berzelius

Question 17.
Symbol for Tungsten is and it is ……………….. and it is derived from its German name ……………….. .
Answer:
W, Wolfram

Question 18.
22-carat gold is an ……………….. of gold.
Answer:
alloy

Question 19.
……………….. of a compound is a short form of its name written using symbols of its constituent elements.
Answer:
Molecular formula

Question 20.
For separating insoluble particles of blood (blood cells) from its liquid part (plasma), ……………….. method is used.
Answer:
centrifugation

Give scientific reason.

Question 1.
Saltwater is a mixture.
Answer:

1. The salt and water are mixed to give saltwater and can both be separated.
2. It can be separated by boiling saltwater.
3. Water can be obtained by condensation whereas the salt will be leftover.
4. As the salt and water do not react chemically and they are separated by simple processes therefore saltwater is called a mixture.

Question 2.
Classify the following substances according to their properties
(water, thermocol, soil, iron, coal, paper, rubber, copper, coir, plastic)
Answer:

Metals	Mixtures	Compounds
Copper, Iron	Soil, Thermocol	Paper, Coir, Plastic, Rubber, Water

Can you tell?

Answer the following questions:

Question 1.
What are objects made of?
Answer:
An object is made of a certain substance, (i) The term matter is also used as a synonym of substance, (ii) Object is made of matter.

Question 2.
What are these articles of everyday use made of?
Answer:

• Electric wire → copper-metal
• Kitchen utensils → stainless steel, Brass-alloy (aluminium-metal).
• Nails → iron-metal
• Tables, chairs → wood, plastic
• Sugar → sucrose
• Window panes → glass
• Salt → NaCl (Sodium chloride) it is a compound.

Question 3.
What do the short-forms Dr, H.M., AC, Adv., C.M., DC stand for?
Answer:
Short forms of Dr. – Doctor, H.M. – Headmaster, AC – Air conditioner, Adv – Advance, C.M. – Chief Minister, DC – Direct current

Question 4.
Which metals do we use in day-to-day life?
Answer:

• Gold and silver → used in jewellery, computer and solar cells
• Iron, copper, aluminium → used to make utensils
• Copper → used in electrical gadgets
• Tungsten → used in electric bulbs.
• Zinc → for coating on iron to prevent rusting
• Tin → for coating on copper and brass vessels
• Iron → nails, agricultural equipments, in construction of buildings, to make steel

Question 5.
Are metals elements?
Answer:
Yes, metals are elements.

Question 6.
Which element helps combustion?
Answer:
Oxygen helps combustion.

Question 7.
Does water help combustion?
Answer:

1. Water is formed by a combination of hydrogen and oxygen but does not help combustion.
2. It is used to extinguish a fire.

Question 8.
What are the mixtures used in everyday life?
Answer:
Oil and water, lemon juice and sherbet, bhel, honey and tea, milk and chocolate, coffee and cream, salt and water, smog (smoke + fog) air (oxygen + nitrogen), salad, milk.

Question 9.
Are all mixtures useful to us?
Answer:
No, adulterated foodstuff is also a kind of mixture and it is not useful. It is harmful, because when an unwanted and harmful substance is mixed with another substance the resulting mixture no longer remains useful.

Question 10.
How will you separate each component from a mixture of semolina, salt and iron filings?
Answer:

1. If a magnet is moved through this mixture all iron filings will stick to the magnet, remove them.
2. Add water to the remaining mixture, all salt will dissolve and then filter through filter paper.
3. Samolina will settle in filter paper.
4. The filtrate will be saltwater and salt can be separated by evaporation or distillation.

Use your brainpower!

Answer the following questions:

Question 1.
In day to day life we come across many things in our surroundings. We touch them, we study their properties. Are all these things made from only one kind of matter or from more than one kind of matters?
Answer:

1. Things are made from only one kind of matter or may be made from more than one kind of matter.
2. When a matter is made up of only one type of atoms it is called an element.
3. We find many elements in our surroundings.
4. But we also see many substances which are made up of two or more elements they are called compounds.
5. Also we see many substances which are formed by physically mixing two or more elements, they are called mixtures.

Question 2.
Classify the following according to the nature of matter in them – whether it is made from one kind of matter or from more than one kind of matter, and whether it is in solid, liquid or gaseous state: an engraved idol, gold, milk, water, a plank, concrete, salt, soil, coal, smoke, sherbet, cooked khichadi, steam.
Answer:

Question 3.
Which of the following are mixtures?
(water, sharbet, iron, steel, coal, air, salt, copper, brass, soil)
Answer:
Mixtures: sherbet, steel, air, brass and soil

Question 4.
Which elements are present in air?
Answer:
Nearly all of the earth’s atmosphere is made up of gases → Nitrogen, Oxygen, Carbon dioxide, Argon and Neon, Helium and Krypton.

Question 5.
Is carbon dioxide an element?
Answer:
No, carbon dioxide is a compound. A molecule of the compound CO₂ contains one atom of the element carbon and two atoms of the element oxygen.

Question 6.
What are the properties of elements due to?
Answer:
Properties of elements are due to molecules present in it. The molecules are made of one or more atoms which are exactly alike. The mass and volume of atoms of different elements are different.

Question 7.
Are the atoms of different elements similar or dissimilar?
Answer:
The atoms of different elements are dissimilar.

Question 8.
Is the water that falls from clouds naturally pure?
Answer:

1. Any form of water that falls from the clouds is known as precipitation. Several forms → rain, snow, hail stones.
2. Yes, it is pure as water vapours condense to form rain.
3. The same process is used in distillation to obtain the purest water.

Question 9.
Which properties of a liquid are seen in the distillation method?
Answer:
Liquid when boiled turns into gaseous state (e.g. water vapours) and on cooling it condenses to liquid.

Question 10.
For what purposes is distilled water used?
Answer:
Distilled water is used in pharmacy as a solvent, in photography to wash the negatives, in laboratory experiments and in cleaning medical tools.

Answer the following questions:

Question 1.a.
Take a piece of chalk and keep on dividing it in to smaller pieces, what will happen?
Answer:
We will get very tiny particles of chalk.

Question b.
Wipe a drop of ink with a handkerchief what effect does it have on the cloth of the handkerchief?
Answer:
The cloth will absorb the ink drop and cloth will have a stain mark on it.

Question c.
What happens when the lid of a bottle of perfume is opened?
Answer:
The molecules of perfume move out of the bottle and collide with other molecules in the air and eventually perfume spreads throughout the room.

Question 2.
Fill water in a spray pump, spray the water and observe the spray.
Answer:
When we spray the water, spray is composed of small particles of water. They are very tiny that we can not see them.

Question 3.
Take water in a tea pot and cover it, heat the water to a boil. What do you see on the inside of the lid?
Answer:

1.  When we boil the water in a tea pot it boils and changes into gaseous state.
2. We find vapours (steam) but when we cover it with a lid, the water vapour cools down, condenses into liquid. So we find water droplets on the inside of the lid.

Question 4.a.
Take sugar in a test tube and heat the test tube. Observe what happens. What remains behind?
Answer:
When a test tube containing sugar is heated, the sugar melts and then it loses water leaving behind a black substance. This black substance is carbon.
Sugar is sucrose, a molecule of sugar is composed of 12 atoms of carbon, 22 atoms of hydrogen and 11 atoms of oxygen. (C₁₂H₂₂O₁₁).

1. Sugar is a compound made from these three elements carbon, hydrogen, oxygen.
2. It is a Carbohydrate.

Question b.
Using tongs hold a magnesium ribbon in a flame and observe what changes took place?
Answer:
When a magnesium ribbon is ignited, light and heat are produced. Magnesium reacts chemically with oxygen in the air
2Mg_(s) + O_2(g) → 2MgO_(s)
Magnesium oxide is produced.

Question c.
What does the name carbon dioxide imply – how many and which elements is this substance made of?
Answer:

1. Carbon dioxide is a compound. It is a tasteless, odourless gas. It is a natural product of respiration.
2. Plants use this to produce food.
3. Humans breath out the CO₂.

[A molecule of the compound carbon dioxide contains one atom of the element carbon and two atoms of the element oxygen.]

Question d.
Which of these are compound, which are elements?
Answer:

• Water → compound H₂O (hydrogen + oxygen), Oxygen → Element
• Carbon dioxide → compound CO₂ (Carbon + Oxygen)

Question e.
What is the smallest particle of a compound called?
Answer:
The smallest particle of a compound is called molecule.

Question 5.
From the internet or reference books obtain information about elements and prepare a table according to the format given below:
Answer:

Question 6.
Some methods of separating the components of a mixture.

Answer:

1. Winnowing
2. Filteration
3. Hand picking
4. Churning
5. Sieving

Question 7.
What is a molecular formula?
Answer:
Like an element, a compound is also written in an abridged form. A molecule of a compound is formed by a chemical combination of atoms of two or more elements. Therefore a molecular formula is used to represent a compound. Molecular formula of a compound is a short form of its name written with the help of the symbols of constituent elements and the number of their respective atoms, e.g.: Nael – Sodium chloride.

Question 8.
Collect information and prepare table:

Write short notes on:

Question a.
Atoms
Answer:
Atoms are basic building blocks of matter. Desk, chair, air are made up of atoms.

Question b.
Compounds
Answer:
1. A compound is a pure substance that contains two or more elements. Compounds are chemical combination of elements with properties that are different from the elements that formed them.
2. Substance is a compound only if its molecules are made up of atoms of different types e.g. Water, one molecule of water is made of two atoms of hydrogen and one atom of oxygen.

Question c.
Mixtures
Answer:

1. A mixture is two or more elements or compounds which are combined physically but no chemical reaction occurs.
2. This means you can separate them again, e.g. air, brass.

Question 9.
Write short notes on:
(1) Distillation (2) Sublimation (3) Magnetic separation (4) Sedimentation (5) Filtration (6) Evaporation
Answer:
1. Distillation: It is a process of heating a solution containing soluble solids to form vapours of the liquid and then cooling the vapours to get the liquid back. e.g. A mixture of common salt and water is taken in distillation flask and heated. Steam rises up and comes out into condenser.

2. Sublimation: It is a process in which some solids on heating are transformed directly to vapour without passing through the liquid state, (i) It is used to separate a mixture of solids. The vapours are cooled separately, (ii) Used to separate ammonium chloride, iodine, camphor and sulphur from any mixture.

3. Magnetic separation: A mixture with iron fillings as one of the components can be separated using magnet to attract the iron particles away from the mixture.

4. Sedimentation: (i) It is a process of separating an insoluble solid from a liquid in which it is suspended, by allowing it to settle to the bottom of the container, e.g. Muddy water contains heavier particles like sand and soil, (ii) Leave this muddy water undisturbed for some time, (iii) The heavier soil and sand particles settle down and the clear upper water is poured out by decantation.

5. Filtration: It is used for separating insoluble solids from a liquid, e.g. mixture of chalk and water is poured through a filter paper in a funnel while the water gets collected in the beaker below, chalk is retained in the filter paper.

6. Evaporation: It is used for recovering dissolved solid substances from solutions by evaporation e.g. sugar can be recovered from sugar-water.

Question 10.
Name the method you will use to separate the following mixtures:

1. Cream from buttermilk.
2. Mud from muddy water.
3. Stones from grains.
4. Tea leaves from boiled tea.
5. Salt from water.
6. Kerosene and water.
7. Blood cells and plasma.
8. Ink from water

Answer:

1. Churning
2. Sedimentation and decantation
3. hand picking
4. filtration
5. distillation
6. separating funnel
7. Centrifugation
8. Chromatography

Question 11.
Draw the experimental setup of weperation using separating funnel:
Answer:

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 18 Sound: Production of Sound Notes, Textbook Exercise Important Questions and Answers.

Maharashtra State Board Class 7 Science Solutions Chapter 18 Sound: Production of Sound

Class 7 Science Chapter 18 Sound: Production of Sound Textbook Questions and Answers

1. Fill in the blanks:

Question a.
Sound is generated by the rhythmic ……………. of any object.
Answer:
vibrations

Question b.
The frequency of sound is measured in …………….. .
Answer:
Hertz (Hz)

Question c.
If …………….. of sound is decreased its loudness also decreases.
Answer:
intensity

Question d.
A medium is necessary for …………… of sound.
Answer:
generation

2. Match the pairs.

Question a.

Column ‘A’	Column ‘B’
1. Flute	a. Frequency less than 20 Hz
2. Frequency	b. Frequency more than 20,000 Hz
3. Sound level	c. Vibrations in the air
4. Ultrasonic sound	d. Measured in Hz
5. Infrasonic sound	e. Decibel

Answer:

Column ‘A’	Column ‘B’
1. Flute	c. Vibrations in the air
2. Frequency	d. Measured in Hz
3. Sound level	e. Decibel
4. Ultrasonic sound	b. Frequency more than 20,000 Hz
5. Infrasonic sound	a. Frequency less than 20 Hz

3. Give scientific reasons.

Question a.
In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rails.
Answer:

1. It was a technique that worked better in those days when train speed were slower than they are today and when there were more rail joints.
2. When people would put their ear to the rail they could hear vibration caused by the wheels moving over the joints. ,
3. Metal being a solid is an efficient medium for the sound to travel and so the sound can propagate further in the rail than would in air as speed of sound is faster in solids than in air.

Question b.
The sounds generated by a tabla and sitar are different.
Answer:

1. In tabla where leather is fitted, sound gets generated when the leather surface is thumped by fingers or palm.
2. The waves thus created travel in two dimensions. Sitar is having strings attached to pumkin box called sound box.
3. Sounds generated by tabla and a sitar are different because they have different pitch and frequencies.

Question c.
If you were both on the moon your friend will not be able to hear you call.
Answer: Yes, your friend will not be able to hear your call because sound needs a medium for transmission since it is a mechanical wave it cannot travel through vaccum.

1. As there is no air on the moon and sound is actually vibration in air.
2. So astronauts communicate to each other by signals or microphones in space even when they are closer.

Question d.
We can hear the movement of a mosquito wings but we cannot hear the movement of our hands.
Answer:

1. Humans cannot hear frequency less than 20 Hz. In the movement of hands oscillations does take place but is less than frequency that humans can hear.
2. Mosquitos wings flap in air.
3. When they fly in air it produces buzzing sound in our ears.
4. The movement of mosquito wings produces sound greater than 20 Hz.
5. Sound is the reception of such waves and their perception by the brain.

4. Write answers to the following questions.

Question a.
How is sound produced?
Answer:

1. Sound is generated due to the vibration of an object, e.g. bell, string or diaphragm of a musical instrument.
2. Vibrations are imparted to the molecules in the air. These vibrations reach our ears through the air and sound is heard.
3. Vibrations of an object is necessary for generation of sound.
4. These vibrations in air are called travelling longitudinal waves which we can hear.

Question b.
What does the intensity of sound depend upon?
Answer:

1. The intensity of sound is proportional to the square of the amplitude of vibration, e.g. If the amplitude is doubled the intensity of sound becomes four times.
2. Therefore the loudness or softness of sound is dependent on the intensity of sound and sound level.

Question c.
Explain how the frequency of oscillation is related to the length of a pendulum and the amplitude of its oscillation.
Answer:

1. Given an oscillatory motion to the pendulum, the maximum distance between the original position A of the pendulum and extreme position B or C is called the amplitude of oscillation. AB, AC is the amplitude of oscillation.
2. The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Relation between frequency and length of a pendulum: If the length of the pendulum increases the period of oscillations also increases.
We know time period of oscillations = \(\frac{1}{\text { Frequency }}\)
If time period increases, frequency decreases, therefore, if the length of the pendulum increases frequency will decrease.
Relation between frequency and amplitude: Frequency of oscillation is independent of its amplitude of oscillation.

Question d.
Explain the two ways by which the pitch of the sound generated by a stretched string can be changed?
Answer:
1. A string vibrates with a particular fundamental frequency. It is however possible to produce pitches with different frequencies from the same string.

2. The two properties of the string that affect its frequency are length and diameter.

3. When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have higher frequency and therefore higher pitch.

4. When a musician presses her finger on a string, she shortens its length. The more fingers she adds to the string, the shorter she makes it, higher will be the pitch.
Diameter: Thick strings with large diameter vibrate slower and have lower frequency than the thin ones.

Project:

Question a.
The bat, a mammal, flies during the night manoeuvering with the help of the ultrasonic sounds it produces. Find out more about this.

Class 7 Science Chapter 18 Sound: Production of Sound Important Questions and Answers

Fill in the blanks:

Question 1.
Bats detect the obstacles in their path by receiving the reflected ………….. .
Answer:
ultrasonic waves

Question 2.
An object that moves back and forth is called ……………. .
Answer:
an oscillator

Question 3.
If the length of a pendulum is increased the time period of oscillation ………………. .
Answer:
increases

Question 4.
The …………… of a wave is the maximum distance moved by the object on either side of the mean position.
Answer:
amplitude

Question 5.
Sound waves do not travel through ……………… .
Answer:
vaccum

Question 6.
The frequency above which sound is not audible to the human ear is …………….. .
Answer:
50,000 Hz

Question 7.
Number of vibrations in a second is called …………….. .
Answer:
frequency

Question 8.
Higher the frequency greater will be the ………….. .
Answer:
Pitch

Question 9.
The loudness of sound depends on ………….. .
Answer:
amplitude

Question 10.
Loudness of sound is measured in units of ………………. .
Answer:
decibel dB

Question 11.
100 hertz is equal to hundred oscillations in ………………. .
Answer:
one second

Name the following:

Question 1.
The sound frequencies above 20,000 Hz.
Answer:
ultrasonic

Question 2.
The medium through which sound is most clearly propagated.
Answer:
solids

Question 3.
The range of frequency in which humans can hear sound.
Answer:
20 – 20,000 Hz

Question 4.
The sound level physically painful to humans.
Answer:
above 100 dB

Question 5.
The technique used by bats to find their way.
Answer:
echolocation

Question 6.
The unit of frequency of sound.
Answer:
Hertz

Question 7.
The unit of sound level or intensity.
Answer:
Decibel

Question 8.
The scientist in whose honour was the unit decibel named for intensity of sound.
Answer:
Alexander graham Bell

Question 9.
Bats and dolphins can hear these sound frequencies.
Answer:
Ultra sonic sound

Question 10.
The sound frequencies used in RADAR systems.
Answer:
Ultra sonic sound

Answer in one or two sentences:

Question 1.
How is sound produced?
Answer:
Sound is produced by vibration of an object.

Question 2.
What produces sound in human beings ?
Answer:
The vibration of the vocal chords in our larynx or voice box produces sound.

Question 3.
What is oscillatory motion?
Answer:
To and fro motion of an object (oscillator) on either side of a central position is called oscillatory motion.

Question 4.
What is periodic motion?
Answer:
The motion of an object repeated again and again at fixed intervals of time is called periodic motion.

Question 5.
What is frequency of oscillation?
Answer:
The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Question 6.
How is intensity of sound and amplitude of vibration related?
Answer:
The intensity of sound is proportional to the square of the amplitude of vibration. For example, if the amplitude is doubled the intensity becomes four times as much.

Question 7.
What happens if the frequency of sound is greater than 1000 Hz or 100 dB?
Answer:
If frequency of sound is increased more than 100dB, the hearing can be temporarily affected which can result in temporary deafness.

Question 8.
What is infrasonic sound?
Answer:
A sound with a frequency less than 20Hz is called infrasonic sound.

Question 9.
What is application of ultrasonic sound?
Answer:
Ultrasonic sound is used in ships as a system known as ‘SONAR’ to detect the obstacle beneath the ocean as well as the depth of an ocean.

Question 10.
What is the difference between pitch and frequency?
Answer:
Pitch is directly proportional to the frequency of a sound whereas frequency is the repeating vibrations per unit time.

Question 11.
What happens when the rubber band is stretched with a greater force and released?
Answer:
When a rubber is stretched with a greater force and released, the amplitude increases which in turn result in a louder sound being generated.

Question 12.
What happens to frequency if the amplitude is changed?
Answer:
The frequency remains the same even if the amplitude is increased or decreased.

Define:

1. Echo: It is a repetition of sound due to the reflection of original sound by a large and hard obstacle.
2. Frequency: It is defined as the number of vibrations per unit time.
3. Hertz (Hz): One hertz is one vibration per second.
4. Ultrasonic vibration: Sounds of frequency higher than 20,000 Hz are called the ultrasonic.
5. Time period: The time taken by an object to complete one oscillation is called time period.
6. Amplitude: The distance between the mean or central position to the extreme position of an oscillator on either side is called amplitude.

Say True or False with explanation:

Question 1.
Sound cannot travel in vacuum.
Answer:
True. Sound needs a medium to travel through. Since vacuum does not provide any medium, sound cannot travel through it.

Question 2.
If the amplitude of vibration is large, sound is feeble.
Answer:
False. When the amplitude of vibration of a sound is large, the sound is very loud. The sound is feeble, when the amplitude is small. Loudness of a sound is proportional to the square of the amplitude of its vibration.

Question 3.
For human ears, the audible range is 2 Hz to 20,000 Hz.
Answer:
True. Human being can hear sounds only within the range of 20-20,000 Hz. We cannot hear the sound having frequency out of this range.

Question 4.
The lower the frequency of vibrations the higher is the pitch.
Answer:
False. Pitch of sound increases when the frequency of vibration increases. The pitch of a sound is directly proportional to its frequency.

Question 5.
Unwanted or unpleasant sound is termed as music.
Answer:
False. Unwanted, or unpleasant sounds are termed noise. Sounds which are melodious, and pleasing to ears are called music.

Question 6.
Noise pollution may cause partial hearing impairment.
Answer:
True. Unwanted, unpleasant sounds are called noise. If one is subjected to noise continuously for a long time, one may suffer from partial hearing impairment.

Question 7.
Time taken by an object to complete one oscillation is called time period.
Answer:
True. Time taken by an object to complete one oscillation is called time period.

Solve the following problems:

Question 1.
A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Answer:
Frequency is the number of oscillations per second of a vibrating body.

The time taken to complete one oscillation (to and fro) is known, as time period.

Question 2.
The sound from a mosquito, is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?
Answer:
The time taken to complete one oscillation (to and fro) is know as time period.

Give scientific reasons:

Question 1.
Loud speakers should not be put in congested areas.
Answer:

1. The loudness or softness is indicated by the intensity of sound and sound level.
2. By putting loud speakers in congested areas, the intensity of sound being more than 100 dB will cause ill effects like temporary deafness and a prolonged exposure can lead to permanent damage.

Answer the following:

Question 1.
Why are the ceilings of concert halls curved?
Answer:
The ceilings of concert halls are curved because sound after reflection from the ceiling it reaches all the comers of the hall and is audible to each person in the hall.

Question 2.
Have you ever heard the sound of movement of hands and falling of leaves from a tree?
Answer:

1. The term infrasonic refer to sound waves below the frequencies of audible sound i.e. under 20 Hz.
2. Humans cannot hear infrasonic sound.
3. Movement of hands and falling of leaves comes below this audible range. Therefore we cannot hear these sounds.

Question 3.
How can dogs perceive in advance the signals of an impending earthquake?
Answer:
Dogs can hear sounds upto about 65,000 Hz. That’s why dogs can receive ultrasonic sound signals produced by the vibration of the earth and start barking in advance before the actual earthquake is felt.

Question 4.
State the uses of Ultrasonic sound.
Answer:
Uses of Ultrasonic sound are:

1. To clean delicate ornaments and the tiny parts of a watch.
2. To observe internal organs of the body.
3. To detect tumors in the brain.
4. To detect faults in a metal.
5. In RADAR systems
6. To Kill certain microbes and insects.
7. SONAR (Sound navigation and ranging) is used to locate the seabed or the position of a ship.

Use your brainpower!

Answer the following questions:

Question 1.
Will a sound be generated no matter how the ruler is kept on the table.

Answer:

1. No, If the ruler kept on the table is only a little part off the table, it will not vibrate with a greater force.
2. On the contrary if the ruler is kept with a larger portion off the table it will vibrate with a greater force generating louder sound.

Question 2.
Is there any correlation between the length of the free part of the ruler and the sound generated?
Answer:
Yes, vibrating ruler pushes the molecules in the air producing sound waves. More the length of free part of ruler less will be the vibrations and less will be the frequency and pitch of the sound. If the length of free part of ruler is shorter it vibrates more quickly producing sound of higher frequency and pitch.

Question 3.
If the ruler is plucked while it is held with 25 cm of it off the table, does it makes any sound? If there is no sound, look for the reason why it is so?
Answer:
No, the ruler vibrates very slowly, which has frequency which is not audible.

Question 4.
What would be the difference perceived between hearing only two pupils in the class talking to each other and all the children talking to one another at the same time?
Answer:

1. When two pupils talk to each other, the sounds of two frequencies produced can be heard clearly.
2. When all the children talk to one another sounds of many frequencies produced can not be heard clearly.
3. Sound level will be more creating loud noise.

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

Maharashtra State Board Class 7 Science Solutions Chapter 13 Changes – Physical and Chemical

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

1. Distinguish between the following.

Question a.
Physical change and Chemical change
Answer:

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

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

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

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

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

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

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

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

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

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

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

3. Give reasons.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Project:

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

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

Fill in the blanks and rewrite the sentences:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Define the following.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Name or Give two example of:

Question 1.
Two physical changes.
Answer:

1. Melting of wax
2. Melting of ice

Question 2.
Two chemical changes.
Answer:

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

Question 3.
Two periodic changes.
Answer:

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

Question 4.
Two non-periodic changes.
Answer:

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

Question 5.
Two reversible changes.
Answer:

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

Question 6.
Two irreversible changes.
Answer:

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

Question 7.
Two natural changes.
Answer:

1. Lighting in the sky.
2. Earthquake.

Question 8.
Two manmade changes.
Answer:

1. Baking bread
2. Cooking food.

Question 9.
Two useful changes.
Answer:

1. Ripening of mango
2. Curdling of milk.

Question 10.
Two harmful changes.
Answer:

1. Spoiling of milk.
2. Air pollution.

Match the following:

Question 1.

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

Answer:

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

Question 2.

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

Answer:

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

Distinguish between the following.

Question 1.
Reversible change and Irreversible change
Answer:

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

Under which different types can be following changes be classified:

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

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

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

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

Question 5.
Burning of Camphor.
Answer:
Chemical change

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

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

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

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

Question 10.
Heartbeat.
Answer:
Periodic change

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

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

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

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

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

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

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

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

Give reasons:

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

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

Can you tell?

Answer the following questions:

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

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

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

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

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

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

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

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

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

Use your brainpower!

Answer the following questions:

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

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

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

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

Examples:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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