Problem: Evaporation of sweat requires energy and thus take excess heat away from the body. Some of the water that you drink may eventually be converted into sweat and evaporate. If you drink a 20-ounce bottle of water that had been in the refrigerator at 3.8 °C, how much heat is needed to convert all of that water into sweat and then to vapor?? (Note: Your body temperature is 36.6 °C. For the purpose of solving this problem, assume that the thermal properties of sweat are the same as for water.)

FREE Expert Solution

We’re being asked to calculate the amount of heat required to convert the 20 oz of water to vapor


Converting 20 oz to grams (1 oz = 20.35 g)


20 oz 28.35 g1 oz= 567 g



1. q1 which is the heat in raising the temperature of  567 g of water from 3.8˚C to 36.6 ˚C

2. q2 which is the heat in raising the temperature of  567 g of water from 36.6˚C to 100 ˚C

3. q3 which is the heat in evaporating 567 g of water at 100˚C


We need to solve for each heat individually then add them together to get the final answer.


For q1: The temperature changes from 3.8 ˚C to 36.8 ˚C. Because of this, the equation we’ll use is:


q = mCT


where m = mass (in g), cliq = specific heat of water (in J/g • ˚C), and ΔT = change in temperature (final T – initial T)


We’re given the following values:

m = 567 g                 cliq = 4.18 J/g • ˚C                ΔT = 36.8 ˚C – 3.8 ˚C = 32.8 ˚C


Calculating for q1:


q = mCTq = (567 g)(4.18 Jg°C)(32.8°C)q = 7.77x104 J



For q2: The temperature changes from 36.8 ˚C to 100 ˚C. Because of this, the equation we’ll use is:


q = mCT


where m = mass (in g), cliq = specific heat of water (in J/g • ˚C), and ΔT = change in temperature (final T – initial T)


We’re given the following values:

m = 567 g                 cliq = 4.18 J/g • ˚C                ΔT = 100˚C - 36.8 ˚C = 63.2 ˚C


Calculating for q2:


q = mCTq = (567 g)(4.18 Jg°C)(63.2°C)q = 1.50x105 J


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Problem Details

Evaporation of sweat requires energy and thus take excess heat away from the body. Some of the water that you drink may eventually be converted into sweat and evaporate. If you drink a 20-ounce bottle of water that had been in the refrigerator at 3.8 °C, how much heat is needed to convert all of that water into sweat and then to vapor?? (Note: Your body temperature is 36.6 °C. For the purpose of solving this problem, assume that the thermal properties of sweat are the same as for water.)

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Heating and Cooling Curves concept. You can view video lessons to learn Heating and Cooling Curves. Or if you need more Heating and Cooling Curves practice, you can also practice Heating and Cooling Curves practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Sharma's class at UM.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry - OpenStax 2015th Edition. You can also practice Chemistry - OpenStax 2015th Edition practice problems.