NCERT Class 6 Science - Workbook Chapter 6 Changes Around Us

Class VI

Science Workbook

Chapter 6 

Changes Around Us

I. Answer the following questions in brief:

Q.1 State whether the following changes can be reversed or not:

i) Blowing air into a balloon without bursting it. It can be reversed

ii) Baking a clay pot in the oven. It cannot be reversed

iii) Making a flower by paper cutting. It cannot be reversed

iv) Fixing a metal rim on a wooden wheel. It can be reversed

Q.2. Can we bring about a change in a substance without heating it? If so, how?

Ans. Yes we can bring about a change in a substance without heating it. By mixing a different substance on it.

Q.3. A potter shapes a lump of clay into a pot on his wheels and then takes it into an oven. Point out the changes that can be reversed or cannot be reversed in this process.

Ans. Potter shapes a lump of clay into a pot it is reversible change or physical change. When it takes into an oven it is irreversible change or chemical change.

Q.4. Why are metal rims heated to fix them onto the wooden wheels? Can this change be reversed?

Ans. The metal rim is made slightly smaller than the wooden wheel. On heating, the rim expands and fits onto the wheel. Cold water is then poured over the rim, which contracts and fits tightly onto the wheel. Yes this change be reversed.

Q.5. Melting of wax is a reversible change while burning of candle is non-reversible. Justify this statement.

Ans. The melting of the wax is a reversible change as the shape of the wax can be obtained by heating it. While the burning of candle is an irreversible change as the burnt candle thread cannot be obtained.

II. Give one term for each of the following:

a) Changing a solid into liquid by heating. Melting

b) Changing of water vapour into liquid by cooling. Condensation

c) Reduction in size of a substance due to cooling. Contraction

d) Increase in size of a substance due to heating. Expansion

e) Change of liquid water into gas form. Evaporation

III. Fill in the blanks:

a) A change may occur by mixing a substance with some other.

b) We can change a substance by heating it.

c) A change may occur by heating a substance.

d) Some changes can be reversed while others cannot be done so.

e) A substance contracts when it is cooled.

IV. Write whether True or False 

a) The metal ring in tools is made slightly larger than the handle. (False)

b) Separating bran from wheat flour is a change that can be reversed. (False)

c) Stretching a rubber is a change that can be reversed. (True )

d) The size of the metal rim to be fixed on a wooden wheel is slightly smaller than it. (True)

e) On blowing air into a balloon, it bursts. It is a change that can be reversed. (False)

V. Match the following:

Ans.

a) Drying clothes usder the sun - (vi) Evaporation

b) Change of water vapour into liquid - (v) Condensation

c) Reduction in size by cooling - (iii) Contraction

d) Change of liquid water into gas form - (ii) can be reversed

e) Increase in size by heating - (i) Expansion

d) Sprouting of seeds - (iv) can't be reversed

VI. Select the correct alternative:

(i) The metallic rim which is to be fitted onto a wooden wheel should be

Ans - a) slightly smaller that the wheel

(ii) We can bring about a change in a substance by 

Ans - c) Both of these

(iii) Water and sugar are added to obtain sugar solution. We can get the original substances by

Ans - d) Evaporation and Condensation

(iv) Shown below are some activities to bring about changes in substances.

The changes that can be reversed from among these are

Ans - d) IV and I

(H.W.) 

VII. Complete the following word puzzle using the clues given below: