1. Energy

2. Two Types of Energy Potential Energy Kinetic Energy
Stored energy
We only see changes during Phase changes
Kinetic Energy
Energy of motion
Changes whenever there is a change in temperature
Temperature is a measure of Kinetic Energy
What is Absolute Zero?

3. There are two temperature scales that we need to know
Celsius
Water freezes at 0 oC
Water boils at 100 oC
Kelvin
K = oC
Water melts at 273 K
Water condenses at 373 K
What do you notice about the size of a Kelvin and Celsius degree?

4. The first equation you need to work with Heat
Whenever there is a change in temperature
From Table T in your Reference Tables
q = m c  T
Heat, mass, specific heat capacity, and temperature change
Specific heat Capacity for water is listed on Table B.
Remember that  T represents two numbers
What are the two numbers?
What order should they be in?
About the sign of q…
Can it be negative?
What would that mean?

5. An example using the first equation
Example: How much heat is absorbed when 89 grams of water is heated from 298 K to 330 K?

6. The second equation you need has to do with a phase change
solid to a liquid = melting (a.k.a. fusion)
Liquid to a solid = freezing
Equation from Table T in your Reference Tables
q = m Hf
Heat, mass, Heat of Fusion
Heat of Fusion for water is listed on Table B.

7. An example using the Heat of Fusion of Water
What is the mass of a sample of ice that requires 13,400 J of heat to melt?

8. The last equation – for the other phase change
Liquid to a gas = boiling
Gas to a liquid = condensation
Equation from Table T in your Reference Tables
q = m Hv
Heat, mass, Heat of Vaporization
Heat of Vaporization for water is listed on Table B.

9. An example using the Heat of Vaporization of Water
What is the mass of a sample of liquid water that requires 13,400 J of heat to boil completely?

10. Now for another example, and I am not telling you which equation to use
A sample of water that has a mass of 87.4g. if it releases 1249 J of heat and had an original temperature of 89oC, what is the final temperature of the water?

11. A more interesting example
A sample of ice at its freezing point has a mass of 45.0 grams. How much heat is needed to melt the sample and then raise its temperature to 354 K?
Is this endothermic or exothermic?
Draw a Heating/cooling curve that would be associated with this question.

12. Let’s brush up on a couple of concepts
What is happening to the particles of a substance while the temperature is increasing?
What is happening to the particles of a substance when it is…
Melting?
Freezing?
Boiling (Vaporizing)?
Condensing?
Subliming (sublimation)?
Depositing (deposition)?

13. What is a Calorimeter?
An insulated container used for measuring temperature changes
Translation … a Styrofoam cup is usually used in our classes.
The idea is:
Use water to catch all of the heat given off by something
Use our energy equations to determine the amount of energy change in the water

14. An example
A piece of metal with a mass of 24.0g is added to a 100.0g sample of water. The initial temperature of the water is 20.0 oC and the initial temperature of the metal is 100 oC. If the final temperature of the water-metal combination is 40.3oC, what is the specific heat of the metal?