At the end of a warm summer day, imagine you are jumping from the 80°F air into an 80°F swimming pool. Use what you have learned about thermal energy and heat flow to explain which direction heat from your body flows in the air and in the water, and why the pool feels cooler than the air. (10 points) Think about the temperature of your body and the factors that determine whether a substance makes a good thermal conductor.

2. You feel the pool feels cooler because your body temperature drops faster in the water than in the air, due to the higher specific heat capacity of water.

Explanation:

The normal temperature of the body is about 98ºF.

1. Heat direction

The thermal energy always flows from the warmer bodies to the colder bodies. Thus, the heat from your body flows toward the air or the water.

heat flow

body → air or water

98ºF 80ºF

warmer colder

2. Why the pool feels cooler than the air?

Water has a high specific heat capacity. That makes that, for a given amount of heat, it will change its temperature little.

When your body is in water the heat of your body will flow to the water and while the themperature of the water changes little the temperature of your body changes more, in the same time. This is, the rate of cooling of your body is higher than the rate of cooling of the water.

When you compare what happens in air, since air has a lower specific heat capacity, the rate of cooling of your body is lower than in water.

Then, the temperature of your body will decrease faster in the water than in the air, which is what you interpret (feel) as the pool is cooler than the air.