1. Unit 5 Heat Energy Heat energy is the random movement of molecules
Heat and temperature are NOT the same

2. Heat energy
Heat-is a calculated value measured in calories which depends on-
Amount of material
Temperature of material
Type of material

3. Temperature
Temperature is measured in degrees (Celsius, Fahrenheit or Kelvin)
It is a direct measurement of average molecular motion

4. Temperature
Most substances expand when heated and contract (shrink) when cooled
Heating speeds up the movement of molecules, causing them to bump into each other and move apart

5. Water does not follow this rule! It expands when it freezes
Example of this?

6. Phases of matter review
In which phase is water least dense?
A- Gas
B- Liquid
C- Solid

7. Most substances of matter…
A- expand when heated
B-contract *shrink* when heated
C- do not change at all when heated

8. Heating a substance causes the molecules to move….
A- Slower
B- Faster
C- does not affect molecule speed

9. Phases and Phase Changes
Phases- Matter is found in three states dependent on its temperature
1. solid- definite shape
molecules are moving the least
definite volume

10. 2. Liquid no definite shape (takes the shape of its container)
molecules move more
definite volume

11. 3. Gas No definite shape molecules have the most movement
No volume (takes the volume of its container)

12. During a phase change, heat energy is always either absorbed or released
Melting-heat is absorbed (solid changes to a liquid)
Freezing- heat is released (liquid changes to solid)
Vaporization-heat is absorbed (liquid changes to a gas through boiling or evaporation)
Condensation- heat is released
Sublimation- heat is absorbed (solid to a gas (dry ice))

13. Heat Transfer
Heat moves from HOT to COLD until dynamic equilibrium is reached
(same temperature)
3 forms of heat transfer: conduction, convection, & radiation

14. 1.Conduction- heat can be transferred through solids that are touching due to molecules bumping together (collisions)
Examples?

15. 2.convection-heat can be transferred through currents flowing through a liquid or gas
Examples?

16. 3.radiation-heat can transfer through empty space (vacuum) by electromagnetic waves
Examples?

20. There’s no such thing as cold