(al Gases exert pressure on the walls of the container (b) Evaporation causes cooking
Answers
Answer:
Answer (a) Particles of gases move randomly in all directions at high speed. As a result, the particles hit each other and also hit the walls of the container with a force. Thus, a gas exerts pressure on the walls of the container.
Answer (b) Here are some reason that evaporation causes cooling:-
1. The outer walls of the cooler get sprinkled by water constantly. This water evaporates due to hot dry weather. Evaporation causes cooling of inside air of cooler. This cool air is sent to the room by the fan.
2. The earthen pot is porous with lot of pores on it, the water oozes out through these pores and the water gets evaporated at the surface of the pot thereby causing cooling effect. This makes the pot cold and the water inside the pot cools by this process.
3. Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands.
4. Tea in the saucer has larger surface area than in a cup. The rate of evaporation is faster with increased surface area. The cooling of tea in saucer takes place sooner than in a cup. Hence, we are able to sip hot tea or milk faster from a saucer rather than a cup.
5. We should wear light coloured cotton clothes in summer. Light colour because it reflects heat. Cotton clothes because it has pores on it, which absorbs sweat and allows the sweat to evaporate faster thereby giving cooling effect.
Hope it helps.