Science In Everyday Life Solutions for Class 6 Science Chapter 6 Changes Around Us are provided here with simple step-by-step explanations. These solutions for Changes Around Us are extremely popular among Class 6 students for Science Changes Around Us Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science In Everyday Life Book of Class 6 Science Chapter 6 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science In Everyday Life Solutions. All Science In Everyday Life Solutions for class Class 6 Science are prepared by experts and are 100% accurate.

Page No 76:

Question 1:

Write one word for the following

1. A change that can be reversed .....................
2. A change that cannot be reversed .....................
3. A change where no new substance is formed .....................
4. A change where a new substance is formed .....................

Answer:

1. Reversible change
2. Irreversible change
3. Physical change
4. Chemical change

Page No 76:

Question 2:

Identify the changes that occur when the following happen.

1. Freezing of water .....................
2. Making curd from milk .....................
3. Boiling an egg .....................
4. Tearing of paper .....................

Answer:

  1. Freezing of water             physical and reversible change
  2. Making curd from milk    chemical and irreversible change
  3. Boiling an egg                  chemical and irreversible change
  4. Tearing of paper                physical and irreversible change

Page No 76:

Question 1:

Which of these is a reversible change?
(a) Dough to chapattis
(b) Burning of candle wax
(c) Rice grains to cooked rice
(d) Melting of kulfi

Answer:

(d) melting of kulfi
After freezing the melted kulfi, one can get a solid kulfi again.

Page No 76:

Question 2:

Which of these is an irreversible change?
(a) Melting of wax
(b) Freezing of water
(c) Boiling of water
(d) Burning of paper

Answer:

(d) burning of paper
Once the paper is burnt, it cannot be converted to paper again.

Page No 76:

Question 3:

Baking a cake is an example of
(a) physical change
(b) irreversible change
(c) chemical change
(d) both (b) and (c)

Answer:

(d) both (b) and (c)
Baking a cake is a chemical and irreversible change, because once the raw materials are chemically converted during baking, one cannot recover the raw materials from the cake.

Page No 76:

Question 4:

The order of expansion in solid, liquid, and gas
(a) solid > liquid > gas
(b) solid < liquid < gas
(c) solid > gas > liquid
(d) solid < gas < liquid

Answer:

(b) solid < liquid < gas
In solids, particles are closely packed; whereas in gases, particles are loosely packed. Hence, solids have negligible expansion, gases have maximum expansion and liquids have intermediate expansion.

Page No 76:

Question 5:

Expansion gaps are kept in railway tracks because of
(a) expansion of rails in hot weather
(b) contraction of rails in hot weather
(c) expansion of rails in cold weather
(d) contraction of rails in cold weather

Answer:

(a) expansion of rails in hot weather
Expansion gaps are kept in railway tracks because of expansion of rails in hot weather.

Page No 76:

Question 1:

Fill in the blanks with the correct words.
1. Melting of ice-cream is an example of a/an .................... (reversible/irreversible) change.
2. Ripening of fruits is an example of a/an .................... (reversible/irreversible) change.
3. Cooking of foood is an example of a/an .................... (reversible/irreversible) change.
4. Breaking of glass is a .................... (physical/chemical) change.
5. .................... (Heating/Cooling) causes steam to change into water.

Answer:

1. Melting of ice cream is an example of a reversible change.
2. Ripening of fruits is an example of an irreversible change.
3. Cooking of food is an example of an irreversible change.
4. Breaking of glass is a physical change.
5. Cooling causes steam to change into water.



Page No 77:

Question 1:

What are reversible changes? Give two examples.

Answer:

Reversible changes are those changes that can be reversed. Example: Melting of ice and freezing of water.

Page No 77:

Question 2:

Name three physical states of water. How can you convert the liquid state of water into its solid state?

Answer:

Three physical states of water are ice (solid), water (liquid) and steam (gas).
We can convert the liquid state of water into its solid state by cooling it at 0​oC.

Page No 77:

Question 3:

What are irreversible changes? Give two examples.

Answer:

Irreversible changes are those changes that cannot be reversed. Example: Ripening of fruits and burning of paper.

Page No 77:

Question 4:

Why is burning of paper an irreversible change?

Answer:

Burning of paper is an irreversible change because a new substance called ash is left or formed after a paper has been burnt. This new substance differs from the original (paper) in its appearance and properties.

Page No 77:

Question 5:

What are physical changes? Give two examples.

Answer:

Physical changes are those changes in which no new substances are formed. Example: Breaking of glass, freezing of water and tearing of paper.

Page No 77:

Question 6:

What are chemical changes? Give two examples.

Answer:

Chemical changes are those changes in which new substances with different properties are formed. Example: Cooking of food and burning of substances.

Page No 77:

Question 7:

What is the effect of heating and cooling on some materials?

Answer:

Some materials expand on heating, whereas some contract on cooling. Heating makes the particles (that form the material) to expand or to loosen, whereas cooling makes the particles to contract or to tighten.

Page No 77:

Question 1:

Explain why melting of butter is reversible whereas curdling of milk is irreversible.

Answer:

Melting of butter is a reversible change because on freezing, the melted butter changes back to its solid form. Whereas curdling of milk is an irreversible change because on curdling, milk changes to curd and cream, and gets spoilt when not refrigerated, and cannot be changed back to milk by any process.

Page No 77:

Question 2:

Explain why tearing of paper is physical change whereas burning of paper is a chemical change?

Answer:

In tearing of paper, no new substance is formed. Therefore, it is a physical change. Whereas in burning of paper, a new substance called ash is formed. This new substance differs from the original substance (paper) in its appearance and properties. Therefore, burning of paper is a chemical change.

Page No 77:

Question 3:

Give some examples of expansion in solid, liquid, and gas.

Answer:

Examples of expansion in solids: Expansion of railway track in hot weather and expansion of metal bottle cap on heating.
Examples of expansion of liquids: Expansion of water on heating and expansion of mercury in thermometer.
Examples of expansion of gas: Expansion of air in balloon on heating and bursting of cycle tube in hot weather because of expansion of air in it.

Page No 77:

Question 4:

List some examples of contraction in solid, liquid, and gas.

Answer:

Examples of contraction in solids: Tightening of metal cap of bottle on cooling and cracking of hot glass tumbler on sudden cooling.
Examples of contraction in liquids: Thickening of melted butter and chocolate on cooling.
Examples of contraction in gases: Shrinkage of inflated balloon on pouring cold water on cooling.

Page No 77:

Question 5:

Write three different applications of expansion and contraction of materials.

Answer:

Following are the applications of expansion and contraction of materials:

  1. The jammed metal lid of a jam jar can be expanded and opened by heating.
  2. In many thermometers, mercury is used. When the bulb of the thermometer comes in contact with a hot object, the mercury expands and its level rises in the glass tube, indicating the temperature.
  3. The electric lines are never hung tautly between poles because in outside environment wires are subjected to extreme weather conditions, ranging from acute hot to cold temperature. In winters, a taut wire on contraction can snap.



View NCERT Solutions for all chapters of Class 6