1. Energy Many forms and sources
_________________ is interested in heat exchanges
_______ bonds takes energy (___________)
_______ bonds produces energy (________)
SI Unit is the Joule (J), common unit calorie
_____________________
4.18 kJ = 1 kcal

2. Temperature and Energy Change
Every substance has a unique ability to ______________________________
Called _______________.
Water has a very large value.
Specific Heat (cp) is the measure of how much ___________ a substance will absorb or release ______________. 4.18J/g°C for water

3. Q = m cp ΔT Energy = ___________________________
Ex: If 20 g of water changes its temp from 25.0C to 30.0C, what amount of energy is absorbed?
Q = (______) x (______) x (_____)
Q = 418 J

4. Heat of Reaction Energy change that occurs during a chemical reaction
Called __________
Symbol (____) = change in enthalpy
__________ ΔH value = exothermic reaction
_________ ΔH value = endothermic reaction

5. Energy Reactants Products Reaction coordinate ___________ reaction
Overall energy change is negative.
Products
Reaction coordinate

6. Energy Reaction coordinate Endothermic reaction
Overall energy change ____________.
Reaction coordinate

7. Heat of Formation ∆Hf°
The energy change associated with the formation of one mole of a _____________________.
Sometimes uses fractional coefficients
Ex. H2(g) + ½ O2(g) → H2O (l)
∆Hf° = kJ/mol exothermic (comp. is stable)
___________________________
Practice this skill. Important.

8. Calculation of ΔH reaction
Two methods – both work
Hess’ Law and a shortcut
Learn both (use the shortcut more often)

9. Hess’ Law - finding ΔH
Says that if you can write a reaction in steps that add up to the original reaction, ____ ______________ is the sum of the ΔH of the steps. (route independent)
Guidelines
1. If the reaction is reversed, so is the sign of ΔH.
2. If coefficients are multiplied, so is ΔH.

10. Example: find ΔH CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
Solution
1. Write ΔHf eq. for each compound
C(s) + 2H2(g) → CH4(g) ΔH = kJ
C(s) + O2(g) → CO2(g) ΔH = kJ
H2(g) + ½ O2(g) → H2O(l) ΔH = kJ

11. ALTERNATIVE TO HESS’ LAW
Handy shortcut to use for calculations.
ΔH = Σ ΔHf (products) - Σ ΔHf (reactants)
Remember to ________________________ in the balanced equation.
ΔH = ( kJ + _________) – (-74.8 kJ)
ΔH = ________

12. ________________ REACTIONS
Proceed without outside assistance (beyond the initial Ea) -- they just happen.
Spontaneous chemical reactions generally occur if the ____________________________________.
-sometimes this is not the case ( ex---H2O(s) only forms if the temp is less than 0C)
-reason for this is the other driving force in nature

13. Entropy A ___________________ or randomness of a system.
-represented by S (_______________)
ΔS = __________________________

14. All entropies (Sf and Si) are positive, but …ΔS can be negative or positive.
if ΔS is negative ===> _______________ (lower entropy)
Example: ______________ of a liquid
if ΔS is positive ===> _____________ (more entropy)
Example: ___________ of a liquid….. favored in nature!

15. Prediction of entropy change
_______________ of compounds decreases entropy (due to bonding)
decomposition of compounds ________ entropy
mixing a solute and solvent __________ entropy
Solid→ Liquid → Gas ___________ entropy
Ie. __________ of a liquid increases entropy

17. So>>>>>>
Two forces influence the direction of a spontaneous reaction: ΔH and ΔS
when ΔH decreases; _________________.
when ΔS increases; __________________

18. Gibbs Free Energy ΔG
An equation called the “Gibbs equation” compares the values of ΔH and Δ S.
__________________
if _____________; the reaction is spontaneous
if _____________: the reaction is not spontaneous, and will not occur.

19. 4 Possible Cases ΔH ΔS Result: + reaction favored - ____________
- ____________
- rx if ΔH is large
+ rx if ΔS is large
*****Alternative to the Gibbs equation:
ΔG = ΣΔGf (products) - ΣΔGf (reactants)

20. Collision Theory
In order to react molecules and atoms must touch each other.
They must hit each other hard enough to react.
Anything that increase these things will make the reaction faster.

21. Things that Effect Rate
____________________
Higher temperature = faster particles.
More and harder collisions.
Faster Reactions.
More concentrated = molecules closer together.
Collide more often.
Faster reaction.

22. Things that Effect Rate
___________________
Molecules can only collide at the surface.
Smaller particles = bigger surface area.
Smaller particles = faster reaction.
Smallest possible is atoms or ions.
Dissolving speeds up reactions.
Getting two solids to react with each other is slow.

23. Things that Effect Rate
_____________- substances that speed up a reaction without being used up.(enzyme).
Speeds up reaction by giving the reaction a new path.
The new path has a__________________.
More molecules have this energy.
The reaction goes faster.
____________- a substance that blocks a catalyst.