1. Phases of Matter, Energy and Phase Changes

2. Changes in Phase Gas Liquid Solid
Condensation Vaporization (Boiling or Evaporating)
Liquid
Solidification Melting (fusion)
Solid

3. Phase Changes Short Summary video on phases: (1 min)
Applet: (Excellent)

4. Let’s Skip a Phase Sublimation
Directly from the solid phase to the gas phase.
Happens with substances with weak intermolecular forces of attraction
They separate easily!
Ex: CO2(s) dry ice, Iodine
CO2(s) → CO2 (g)

5. Energy
Energy = capacity to do work or produce heat. It can be anything that causes matter to move or change direction.
Many different types of energy
Ex: electrical, thermal, atomic, mechanical
“Chemical” energy is the potential energy stored in the bonds between atoms

6. PE vs. KE Potential Energy stored energy
Energy can be stored in bonds between atoms
Kinetic Energy energy of motion
All atoms are moving and vibrating unless at absolute zero

7. Energy During Phase Changes
Solid Liquid or Liquid Gas
Endothermic
Energy is absorbed and overcomes attractive forces between particles
Add heat

8. Gas Liquid, Liquid Solid
Exothermic
As particles come closer together energy is released
Remove heat

10. Heat Energy
Also called Thermal energy, it makes particles move more as it is added
Measured in Joules or calories.

11. Heat Flow or Transfer
Heat energy travels from an object of higher temp. to one of lower temp. until both reach the same temp.

13. Temperature
Measure of the average kinetic energy (motion) of all the particles in a sample.
Not a form of energy!!!
But if you add heat energy or take it away, it causes particles to move faster or slower and thus changes the temp.
Heat vs Temp.

14. Heat vs. Temperature Teacup vs. Bathtub Both at 25˚C
Which one contains more heat energy?
Which one has the greater average KE?

15. Temperature Scales Used in Chemistry
Celsius
Fixed points of scale based on the freezing point and boiling point of water
0 °C = water freezes, 100 °C = water boils
Kelvin
Scale based on lowest temperature possible
0 K = absolute zero

16. Temperature Scales and Conversions K = ˚C + 273

17. Absolute Zero 0 Kelvin -273° Celsius
Temperature at which particles have slowed down so much they no longer possess any kinetic energy.
0 Kelvin
-273° Celsius

18. Heating & Cooling Curves
Graphically represents temp. changes as heat energy is added or taken away.

19. Label This Graph

20. Interpreting the Graph
The slanted portions = temp is changing
Single phase is heating up or cooling down
KE is changing
The flat portions = temp not changing
Substance undergoing a phase change
PE is changing

21. Heating Curve for Water

22. What is Melting Pt? Boiling Pt?