1. Thermodynamics
Lesson 5: Specific Heat

2. The units of heat are:
Joules
Calories
BTU’s

3. Specific heat
The amount of energy it takes, per unit mass, to raise the temperature of a material by one degree

4. The specific heat of water is 1 calorie per gram
In other words, if you add one calorie of heat to one gram of water, the temperature will go up one degree C (scientists like nice even numbers like this) (Also, scientists like to base things on water)

5. Scientists use calories
BTU’s are units in the English system

6. Water has a high specific heat
Specific heats of materials
Substance specific heat
water
Ice
Benzene
Methanol
ethanol
aluminum
Carbon
silver
gold
That is why it is used as a coolant … like in the radiator of your car

7. Heat follows the Law of Conservation of Energy
Heat (thermal energy) cannot be created or destroyed.
When two things are exchanging heat energy, the total amount of energy must remain the same.
Heat lost by tea = heat gained by ice
No net loss of heat energy

8. A Problem
One liter of water at 10°C is added to 1 liter of water at 80°C.
What is the final temperature of the mixture?
a. 10°C
b. 90°C
c. 5°C
d. 45°C
Is wrong because the mixture cannot be the same temperature of either one.
Is wrong because the mixture cannot be hotter than the hottest one.
Is wrong because the mixture cannot colder than the coldest one.
Is right … it is half way between the two temperatures.
First, subtract the two temperatures – 10 = 70
Then, divide that by the number of liters / 2 = 35
Then, add that to the lowest temperature = 45

9. Another problem
One liter of water at 10°C is added to 2 liter of water at 100°C.
What is the final temperature of the mixture?
Hmmmm…it must be between 10 and 100.
Subtract the two temperatures – 10 = 90
There are 3 liters total, so divide 90 by / 3 = 30
Each liter will be raised 30 degrees or lowered 30 degrees.
Add 60 degrees to 10 degrees = 70 OR
Subtract 30 degrees from 100 degrees – 60 = 70
The final temperature is 70