CL 6_CHANGES AROUND US

Which is a way to make a change happen?

• (a) Heating a substance

• (b) Cooling a substance

• (c) Mixing a substance with another substance

• (d) All of these

Rusting of iron is an example of

• (a) slow change

• (b) fast change

• (c) reversible change

• (d) physical change

Conversion of a solid to a liquid by heating is called

• (a) evaporation

• (b) melting

• (c) condensation

• (d) freezing

Which of the following is not a man-made change?

• (a) Change of day and night

• (b) Burning of fuels

• (c) Drying of clothes

• (d) Tearing of paper

Which of the following is a chemical change?

• (a) Evaporation of water

• (b) Burning of fuels

• (c) Moving of a wheel

• (d) Breaking of a brick

Assertion (A): Burning of matchstick is an irreversible change.

Reason (R): The ashes formed on burning cannot be converted back to matchstick.

• Both A and R are true and R is the correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Assertion (A): The change of water from liquid to steam on heating is reversible

change.

Reason (R): Conversion of liquid into steam is called evaporation.

• Both A and R are true and R is the correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Assertion (A): Small gap is left between the rails of a railway track.

Reason (R): Cooling of substances results in expansion.

• Both A and R are true and R is the correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Whenever a metal is first heated and then cooled, which of the following changes take place?

• (A) First contracts, then expands

• (B) First expands, then contracts

• (C) Cannot be determined

• (D) Both a and b

Expansion and contraction are examples of

• Reversible changes

• Irreversible changes

• Chemical changes

• All of these