1. Phase Changes and Thermochemistry

2. Phase Changes Gas Solid Liquid Vaporization Deposition Sublimation
Condensation
Freezing
Liquid
Solid
Melting

3. Endothermic: a process that absorbs heat.
Feels cold
Melting
Sublimation
Vaporization
Exothermic: a process that releases heat.
Feels hot
Freezing
Deposition
Condensation

4. Energy Diagrams Endothermic Exothermic
Ea- Activation Energy: The energy required for a reaction to proceed.

5. Catalyst
Speeds up a reaction by lowering the activation energy.

6. Molar Heats
∆Hvap – Molar Heat of Vaporization: The energy required to change 1 mol of substance from a liquid to a gas (or amount of heat that needs to be removed to change from a gas to a liquid)
∆Hfus – Molar Heat of Fusion: The energy required to change 1 mol of substance from a solid to a liquid (or amount of heat that needs to be removed to change from a liquid to a solid)

7. Molar Heats of Water ∆Hvap(water)= 40.79 kJ/mol
∆Hfus(water)=6.009 kJ/mol
If you have 32.0 grams of ice, how much heat would you need to change it to water?
32.0 g 1 mol kJ
g mol
= 10.7 kJ

8. Molar Heats of Water
How much energy would need to be released to condense g of steam to liquid water?
20.35 g mol kJ g 1 mol
= kJ

9. Molar Heats of Water
If you wanted to release 52.8 kJ of energy, what mass of steam would you need to condense?
52.8 kJ 1 mol g kJ 1 mol
= 23.3 g