1. Heat In Changes of State of Matter
17.3

2. What happens during a phase change:
When heat energy is added, instead of increasing the temperature (increasing the kinetic energy of the molecules), the intermolecular bonds are broken, changing the phase of the substance.

3. PHASES OF WATER

5. Q = mHf Heat of Fusion (Hf)
Amount of heat necessary to convert a given amount of a solid into a liquid
Q = mHf

6. Fusion Heat that is absorbed for a solid becomes a liquid
Melting, endothermic
Reverse process is Solidification
Heat is released, exothermic

7. Practice Problems Answer 21 and 22 in notes on page 521
Hint 21 is the reverse of 20
Look at the Table on pg.522

8. Heat of Vaporization (Hv)
Amount of heat necessary to vaporize a given amount of liquid at its boiling point
Q = mHv

9. Vaporization and Condensation
When a liquid absorbs heat at its boiling point it will vaporize.
The surroundings cool because the liquid is absorbing heat
Heat of vaporization is 40.7 Kj/mol
Condensation is opposite of vaporization

10. Vaporization and Condensation
Heat of vaporization is endothermic
Condensation is exothermic

11. Practice Problems Answer problems 23 and 24 in notes
Hint you need the molar mass of chloroethane

12. Heat of Solution
Heat changes occur when a solute dissolves in a solvent
An example is a hot pack, which is exothermic
An example of endothermic is ammonium nitrate dissolving in water, frost can form

13. Practice Problems
Answer problems 25 and 26 in your notes

14. Activity
Show on a piece of paper, the changes in states of matter for a piece of ice to go to water vapor and back to ice again.
Use your vocab terms to describe steps in a diagram