1. Thermochemistry
The study of heat energy changes in chemical reactions.
Importance:
1. Safety considerations.
KABOOM!
2. Heat energy used for work.
Examples:
Burn methane to heat home.
Burn gasoline to power car.
Burn coal to produce electricity.
HW 12-1, #1
Kabom link
Bozeman energy transformation

2. Turbine Generator - Generating electric current by moving a magnet rapidly around coiled copper wire
Phet Electromagnetic Induction

3. How does the chemical energy from burning coal generate electricity?
Heat Energy from burning coal → water to steam → steam pushes turbine blades to generate electricity

4. What is Energy? Energy = capacity to do work Work = Force x distance
“working” defn of energy = capacity to make objects move

5. 1st Law of Thermodynamics
Energy can neither be created nor destroyed!
Energy can only be transformed from one form to another.
Also known as the
Conservation
of Energy
Phet skateboard link
Bozeman video link

6. How badly do you want the “Free Stuff?” What could POTENTIALLY happen?

7. Potential Energy (PE) Stored energy due to position
OR chemical composition.
“Position” examples:

8. Potential energy transformed into . . .

9. Kinetic Energy(KE)
Energy of Motion
BUNGEE JUMP LINK

10. Potential Energy (PE) due to Chemical Composition
Trinitrotoluene
Hi PE (Weak bonds, unstable)
Lo PE (Strong bonds, stable)
NO2 bonds are weak; Atoms rearrange to form N2, CO and CO2 gases with strong bonds (+ Carbon)

11. Potential TO become . . .

12. Kinetic Energy (KE)- molecules with higher KE move faster
Product Molecules have Lower PE but much Higher Kinetic energy molecules
FIREBALL LINK

13. HW 12-1, #2 4 2 10 Location PE UNITS KE UNITS TOTAL ENERGY 1 10 2 6 32 6 3 8 4 2 10

14. The Ethanol Cannon: Example of First Law in Action . .
Converting Stored Potential Chemical Energy into Kinetic Energy!

15. C2H5OH + O2 → C2H5OH + O2 have potential energy due to
HW 12-1, #3A,3B
C2H5OH + O2 →
C2H5OH + O2 have potential energy due to
What type of reaction pattern is this?
ANS: Combustion of a hydrocarbon
What are the products?
ANS: CO2 + H2O
CHEMICAL COMPOSITION

16. The reaction between ethanol and oxygen is thermodynamically favorable, yet nothing is happening, why?
The collisions between molecules don’t have enough energy to overcome the activation barrier.
What is happening
What we want to happen
HW 12-1, #3C

17. Meet Mr. Tesla Coil! As electricity travels across the gap between the two nails it will heat the gas molecules past the Ea

18. How does the potential energy (PE) and kinetic energy (KE) of the reactant ethanol and oxygen molecules compare to the PE and KE of the product CO2 and H2O molecules?
Reactants
Products
Hi PE
Lo KE
Lo PE
Hi KE

19. Since final product molecules CO2 and H2O have lower potential energy but higher kinetic energy the difference in energy has been released as heat and light.
Link to gases phet

20. Extra KE pushes cork across room!
Hot gases have higher kinetic energy push outwards against the cork, sending it across the room.
Extra KE pushes cork across room!
Cannon video link

21. HW 12-1, #3D
REACTANTS
PRODUCTS KE KE PE KE PE KE PE PE PE KE KE KE

22. HW 11-4, #3E Lo Hi Lo Hi UNSTABLE STABLE WEAKER STRONGER Property
REACTANTS
PRODUCTS PE KE
STABLE/
UNSTABLE
STRONGER BONDS/ WEAKER BONDS Lo Hi Lo Hi
UNSTABLE
STABLE
WEAKER
STRONGER

23. Reaction Profile Diagram for Ethanol Cannon
HW 11-4, #3F
Hi PE, Lo KE
Lo PE, Hi KE