Sample Questions on Evaporation Cause Cooling

Question 1: Why does everybody wear cotton clothes in summer? 

Solution:

During summer, we perspire (sweat) a lot due to our body’s mechanism of cooling by evaporation of sweat which takes heat from the body and makes the body cool. Cotton, being a good absorber of sweat, absorbs the sweat and helps in increasing the speed of the evaporation by increasing the surface area and exposing it to the atmosphere.

Question 2: How does water keep in the earthen pot (matka) remains cool?

Solution:

When we kept water on the earthen pot (matka), the water molecules evaporate from the several tiny pores of the pot. During this process, it takes the heat from the water and thus the water cools down due to the loss of heat. This is the reason why water kept in earthen pot keep cool.

Question 3: We often sprinkle water on the ground or on the roofs during summer. Why?

Solution:

This is because when we sprinkle water over the ground or roof top, the water from there evaporates taking the heat from the ground or roof top and in the process making it cool.  

Question 4: We are able to sip hot tea or milk on a saucer rather than a cup. Give reasons.

Solution: 

We know that the rate of evaporation increases as the surface area of the liquid increases. Thus, when we put the hot milk or tea on a saucer, the surface of the liquid increases, thus the rate of evaporation of the milk or tea increases and due to increase in the rate of evaporation, more heat is taken from the hot milk or tea and it cools down more rapidly as compared to when it was in the cup and we are easily able to sip the hot milk or tea on saucer rather than a cup.

Question 5: Why does our palm feel cold when we put some acetone or perfume on it?

Answer:

When we pour some acetone or petrol on our palm, the acetone or perfume starts evaporating. In this process, it takes the necessary heat required from our palm and due to loss of heat we feel cold. This is the reason why our palm feels cold when we put some acetone or perfume on it.

Question 6: How do air coolers work on the principle of Evaporation? 

Answer:

This is because of the working mechanism of the air cooler. The air coolers has an exhaust fan which sucks in the dry air of the room inside. In the cooler there is a pad that has been wet by water. The water evaporates from the pad by taking the heat from the dry air thus, in the process making the air cool. This cool air released from the air coolers which circulates inside the room. Thus, air coolers work on the principle of cooling effect caused by Evaporation.

Question 7: We feel cool when we apply hand sanitizers to our hands. Give a reason Why?

Answer:

The sanitizers that we apply over our hand contains alcohol as one of it’s primary constituent and the alcohol evaporates much faster than water. Thus, when we apply hand sanitizers over our hand, the alcohol starts evaporating by taking the heat from our own body and thus, due to the loss of heat from our body, we feel cool.

Question 8: In summer our clothes dry up much quicker compared to winter and monsoons. Why?

Answer:

During summer, the temperature is higher than winter and monsoons and we know that the rate of evaporation is directly dependent on the temperature, so in summer clothes dry up much faster in summer in comparison to winter and monsoon. Another important factor is humidity, in summer humidity in air is much less than that in monsoon, thus clothes dry up slowly in monsoons.  

“How Does Evaporation Cause Cooling?” this question troubled thinkers and philosophers since ancient times when the concept of evaporation was not even named evaporation. But in modern times we know that Evaporation Cause Cooling because the particles (atoms and molecules) present at the surface of the liquid surface absorb energy from their surroundings and transform it into vapour, which then causes the cooling effect. Evaporation is a type of vaporization that occurs on the surface of liquids and includes the transformation of liquid particles into gaseous particles. As a result, this process is considered to be responsible for the change in the matter state of liquids. Thus, when the heat of evaporation is positive cooling is then caused by the evaporation.