1. Thermochemistry is the study of energy changes that occur during chemical reactions and phase changes (changes of state)

2. The Nature of Energy Energy-are we running out?!
Energy is the ability to do work or produce heat
Energy-are we running out?!
Click on the link to watch the video

3. flows due to temperature differences
Energy flows from high to low until…
System E E E E E
System E E E E E
the system reaches dynamic equilibrium
Energy is transferred from one system to the other, this is heat.
flows due to temperature differences
(always hot to cold)

4. Law of Conservation of Energy (aka 1st Law of Thermodynamics)
Energy cannot be created nor destroyed; only converted into different types.

5. Kinetic vs. Potential Energy
Two main types of energy – kinetic and potential
Kinetic – energy of motion
Potential – energy due to position or energy stored in chemical bonds

6. Kinetic vs. Potential Energy

7. Kinetic Energy Thermal energy : comes from heat
Electric: caused by moving electric charges
Sound: energy produced by the periodic movement of matter

8. Potential Energy
Chemical: energy stored in a substance because of its composition
Example: gasoline has lots of C-H bonds to break
Nuclear: nuclear fission or fusion produce energy
Gravitational-positional energy in a gravitational field (not the same as gravity)

9. Temperature vs. Heat Temperature: a measure of the motion in a sample
a measurement of heat.
Heat : total energy of molecular motion, dependent upon amount, size, and type of particles. Heat is energy.

10. Symbol and Units for heat
For heat we will be using little “q”
Heat is energy
Heat = q
Units for heat (q) are:
calories: little calories for science (cal)
Calories: Nutritional Calories (C)
Joules: SI unit of heat(J)

11. Definition of scientific calorie
calorie - the amount of heat required to raise the temperature of one gram of pure water by one degree Celsius.

12. Converting Energy Units
Calorie/calorie/kilocalorie calorie/Joule
1 C = 1000 cal = 1 kcal
1 cal = J
You may write these conversions on your formula sheets

13. The molecules
of the thermometer in hot water should be randomly arranged, slightly further apart, moving faster.
The molecules
of the thermometer in cold water should be randomly arranged, closer together, moving slower.
The molecules of the thermometer in hot water should be randomly arranged, slightly further apart, moving faster.
The molecules of the thermometer in cold water should be randomly arranged, closer together, moving slower.

14. Example 1
A cereal has 155 nutritional Calories per serving. How many calories, kilocalories and Joules is this?

15. Example 2
A person on a diet consumed 1350 Calories in one day. How many calories, kilocalories and Joules is this?