Changes Around Us

The process of converting solid directly into gas is known as _________________________

• Condensation

• Sublimation

• Melting

• Evaporation

Which of the following is a reversible change ?

• Burning of forests

• Ripening of fruits

• Burning of candle

• Melting of ice

Iron rim is made slightly smaller than the wooden wheel. The rim is usually heated before fixing into the wooden wheel, because on heating the iron rim -

• Expands and fits onto the wooden wheel.

• Contracts and fits onto the wooden wheel.

• No change in the size takes place.

• Expands first, then on cooling contracts and fits onto the wooden wheel.

Salt can be separated from its solution (salt dissolved in water), because -

• Mixing of salt in water is a change that can be reversed by heating and melting of salt.

• Mixing of salt in water is a change that cannot be reversed.

• Mixing of salt in water is a permanent change.

• Mixing of salt in water is a change that can be reversed by evaporation.

Melting is a process when -

• Water changes into ice

• Ice changes into water

• Water changes into vapours

• Ice changes into vapours

State whether yes or no.- Can the change in the length of the candle that occurred during burning, be reversed ?

• Yes

• No

Changes can occur by their own also .

• Yes, in every case

• Never

• True

• False

Changes may occur -

• Only by mixing a substance with some other substance

• Only by heating a substance

• Both by heating a substance and by mixing it with some other

• None of these options is correct

The following change can not be reversed -

• Paper aeroplane to a paper

• Fully blown balloon to the balloon

• Baked roti to the ball of dough

• Rolled out roti to a ball of dough

On continuously heating water into a pan -

• The quantity of water in the pan decreases

• The quantity of water in the pan increases

• The quantity of water in the pan remains constant

• Can’t say anything in this case