Question

(a) One day, Suhani was playing with mother's cosmetics. She felt cool, when a liquid bottle broke and some liquid fell on her hand. She got worried. She washed her hand and immediately asked her mother why she felt cold. Her mother answered her.
(i) Can you guess what was that liquid ?
(ii) Why Suhani felt cool when liquid fell on her hand ?
(iii)What values are shown by Suhani's mother?
(b) Rahul is fond of mountaineering. In his summer holidays, he planned to climb a high mountain with his friends. One of his friends got hurt during climbing and required hot water for the treatment. He quickly took out his burner to boil the water. He found that on the mountain water took much less time to boil than on the ground.
(i) Why does water boil at a lower temperature at higher altitudes ?
(ii) What values are displayed by Rahul ?

CBSE Class IX Science LA (5 Marks)

Answer 1

. (a) (i) The liquid is nail paint remover, which contains an ether or acetone.

(ii) She felt cool because ether evaporates by taking heat energy from the hand (body). (iii)She exhibits knowledge, carefulness and educating nature towards her daughter.

(b) (i) Boiling occurs at a point where vapour pressure is equal to the external atmospheric

pressure. At higher altitudes, atmospheric pressure is much less. Less thermal energy is

required to get vapour pressure equal to the atmospheric pressure.

(ii) This shows that Rahul is sympathetic and friendly.