1. Why does a desert cooler cool
better on a hot dry day?
2. How does the water kept in an earthen pot (matka) become cool during summer?
3. Why does our palm feel cold
when we put some acetone or
petrol or perfume on it?
4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
5. What type of clothes should we wear in summer?
Answers
Answer:
1)Evaporation depends on the amount of water vapour present in air (humidity). ... On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. That is why a desert cooler cools better on a hot dry day.
2)Water placed in earthen pots is evaporated from minuscule pores it has as it is made of mud particles. This evaporation of water produces a cooling effect. Some of the heat energy that is generated is used in the process of evaporation. Hence, water stored in earthen pots tends to become cooler in summer.
3)When we put some acetone or petrol or perfume on our palm, it evaporates. During evaporation, particles of the liquid absorb energy from the surface of the palm to compensate for the loss of energy, making the surroundings cool. Hence, our palm feels cold when we put some acetone or petrol or perfume on it.
4)Larger is the surface area more is the evaporation. Thus evaporation is faster in a saucer causing more cooling than in a cup. For this reason, we are able to sip hot tea or milk faster from a saucer than a cup.
5)During summer, we normally wear light coloured cotton clothes. We sweat a lot in summers. Cotton is a good absorber of water. Thus, it absorbs sweat from our body and exposes the sweat to the atmosphere, making its evaporation faster.
Answer:
1.ans The water when evaporated from a desert cooler absorbs energy from the surrounding for compensating the loss of energy during evaporation making the surrounding cool. Evaporation is inversely proportional to humidity. So on a hot dry day, the evaporation is more so the surrounding is more cooled.
2.ans Water placed in earthen pots is evaporated from minuscule pores it has as it is made of mud particles. This evaporation of water produces a cooling effect. Some of the heat energy that is generated is used in the process of evaporation. Hence, water stored in earthen pots tends to become cooler in summer.
3.ans When we put some acetone or petrol or perfume on our palm, it evaporates. During evaporation, particles of the liquid absorb energy from the surface of the palm to compensate for the loss of energy, making the surroundings cool. Hence, our palm feels cold when we put some acetone or petrol or perfume on it.
4.ans Larger is the surface area more is the evaporation. Thus evaporation is faster in a saucer causing more cooling than in a cup. For this reason, we are able to sip hot tea or milk faster from a saucer than a cup.
5.ans During summer, we normally wear light coloured cotton clothes. We sweat a lot in summers. Cotton is a good absorber of water. Thus, it absorbs sweat from our body and exposes the sweat to the atmosphere, making its evaporation faster.
Explanation: