Question

Assertion: Evaporation causes cooling
Reason: Particles of liquid absorb energy from the surrounding to regain the energy lost during evaporation.
A. Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
B. The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
C. Assertion is true but the Reason is false.
D. The statement of the Assertion is false but the Reason is true

Answer 1

Hint: To answer this question, we should know about the process of evaporation. We should know that evaporation is the process by which water changes from a liquid to a gas or vapour.

 Step by step answer:
Evaporation is the process by which an element or compound present in its liquid state changes to its gaseous state below the temperature at which it boils. Let us take the example of water; evaporation is the process by which liquid water enters the atmosphere as water vapour. The rate of evaporation depends on the temperature difference between the evaporating surface and the air, the relative humidity, and wind.
We should note that liquid evaporating from a surface has a cooling effect. And also we can say that different liquids have this effect of cooling. For example, when we rub alcohol, it has more cooling effect than water. Alcohol evaporates comparatively more quickly than water, so scientists put it in the category of volatile liquid. We should understand that when a liquid evaporates, its molecules convert from the liquid phase to the vapour phase and escape from the surface. In evaporation, heat plays a major role.
 Now, we will understand why evaporation has a cooling effect. When molecules leave the surface as vapour, it takes heat energy with it. The heat that it takes with it comes from the surface from which it evaporated. And now we can say that, as these molecules are taking heat with it as they leave the surface, this has a cooling effect on the surface left behind. This makes it easy to understand evaporative cooling.

So, from the above paragraph we now confirm that the reason for the assertion is correct. In question, the assertion was that evaporation causes cooling. And the reason for this was given that when particles of liquid absorb energy from the surrounding to regain the energy lost during evaporation. So, the reason is absolutely correct for this reason. From this we can say that option A is correct.

Note: When we sweat, known by human perspiration, we feel coolness during this perspiration. This is because; we have pores in our skin from which liquid water that is present internally in our skin escapes and is converted to water vapour in the air. As this happens, it cools down our skin surface. This happens almost constantly as temperature rises. Suppose, we enter the atmosphere, which is hotter than what is comfortable for us, the degree of sweating or we can say perspiration or evaporation increases. And as it proceeds further the cooling effect increases. The more we sweat, the more water molecules will escape from our skin surface and from our pores, the more cooling effect we will feel.