Question

(a) Give reason far the following
(i) Why do we see droplets of water on the outer surface of a glass containing ice-cold water ?
(ii) After a hot sunny people sprinkle water on the roof or open err ura
(b)Describe an activity with labelled diagram to illustrate the effect of increase of temperature on
ice.

CBSE Class IX Science LA (5 Marks)

Answer 1

(a) (i) When water vapour in the air comes in contact with cool surface, it loses water content and gets condensed. Hence, we see droplets of water on the outer surface of a glass containing ice-cold water. 1 (ii) Evaporation leads to decrease in temperature because water takes heat for evaporation from the floor. 1 (b) Take about 150 g of ice in a beaker and suspend a laboratory thermometer so that its bulb is in contact with the ice. ➢ Start heating the beaker on a low flame. ➢ Note the temperature when the ice starts melting. ➢ Note the temperature when all the ice has converted into water. ➢ Record your observations for this conversion of solid to liquid state. ➢ Put a glass rod in the beaker and heat while stirring till the water starts boiling. )=' Keep a careful eye on the thermometer reading till most of the water has vaporised.

Answer 2

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