# Question 72a44

Sep 11, 2017

400 calories
or 1674 J

#### Explanation:

Water is our standard unit of measuring heat energy. The amount of energy it takes to change the temperature of 1 gram of water by 1º C is called a calorie. More formally we would say that the specific heat of water is 1 calorie per gram.

So, 200 grams of water cooled by 20 degrees requires removing 4000 calories.

4000 " Cal" = (200" g")/(20" C"º) * (1 " Cal")/( 1" g")#

Since that was over 10 minutes, the amount of heat removed will be just 400 calories per minute.

The more common unit for heat energy is the Joule. 1 calorie is equal to 4.184 Joules.

$400 \text{ Cal" *( 4.18 " J")/" Cal" = 1674 " J}$

This answer assumes that the water is in liquid form during this process. If the water approaches 0º C, you will need to consider the latent heat of fusion.