1. Heat, Temperature & Specific Heat

2. Thermal Energy Total energy in molecules of a substance including
a) kinetic E of moving molecules
b) potential E stored in chemical bonds

3. Temperature = Average kinetic energy per molecule
Average speed of molecule
KE = ½ m V m = mass V = velocity
Velocity or speed is most important
0 velocity = absolute 0….no motion of particles

4. Heat = Flow of thermal Energy from hot to cold
Energy of internal motion of molecules as it transfers from 1 object to another
Transfer of kinetic energy from one molecule to another

5. Laws of Thermodynamics
1) Energy can not be created or destroyed
only converted from one form to another
or transferred from one place to another
2) Heat energy flows from high temperature areas to low temperature areas only

6. Thermal equilibrium
No net flow of heat energy because all areas are the same temperature
Heat flows from hot to cold until….
Thermal equilibrium is reached….
Then it just passes back and forth
Still moving so still heat!

7. Thermometers… Measure their own temperature
Put thermometer in water. Heat flows
Molecules of alcohol speed up and expand or
slow down and contract
Thermal equilibrium between thermometer and water causes red line to stop moving.

8. Measurments & Units Temperature is measured in… o Celsius
Heat is measures in….
calories
1 calorie =
the amount of heat needed
to raise the temp of 1ml H2O
by 1 o C

9. The Calories in your food are Calories,
They are actually Kilocalories =
the amount of heat needed to warm up 1,000 ml of H2O by 1 oC

10. Specific Heat
It takes more heat energy to increase the temperature of some substances.
We say those substances have a high specific heat.
Water has very High specific heat
Specific heat is measured in cal/ml/oC
or cal/g/oC

11. Specific Heat High specific heat warms up slower AND Cools off slower
More massive

12. Heat is Transferred in 3 ways
1) Conduction – objects touch, direct heat transfer from warm object to cold object
2) Convection – heat transferred by flowing molecules
3) Radiation – electromagnetic waves =
Infrared light waves
heat waves, not visible

13. 1) Conduction Metals are good conductors because their
electrons are loosely held (can flow)
Non-metals hold their electrons tightly so are poor conductors called…
insulators

14. 2) Convection
warm , fast moving molecules rise carrying heat with them
(they expand & become less dense)

15. 3) Radiation
Electromagnetic waves
=light waves
Not visible
Heat waves

17. Heat transfer causes phase change
Lowest energy = solid
a) strongest intermolecular forces
b) molecules vibrate in place so
definite shape and volume
Medium energy = Liquid
a) weaker intermolecular forces allow
molecules to flow around each other
so no definite shape
b) still to low energy for molecules to
break away completely and expand
so definite volume

18. Highest energy = gas
a) weakest intermolecular forces
b) molecules can flow & expand
c) no definite shape or volume

19. Phase changes :
Change in amount of thermal energy cause molecules to move in different ways
Higher energy =
weaker intermolecular forces
as molecules expand
Mass does not change
Density changes

20. Phase Change Diagram to be in that phase Solid Liquid Gas low high
x = Heat energy (per mole) needed
to be in that phase

21. Phase Change Diagram: Water

22. Warming A-B Warming ice Add E, Temp B-C Melting Add E, no ∆ Temp
E used to break intermolecular forces so molecules can flow

23. Warming C-D Warming water Add E, Temp D-E vaporization
Add E, no ∆ Temp
E used to break intermolecular forces so molecules can expand

24. Vaporization changes liquid to gas
Boiling
Bubbles of gas form at bottom of liquid
Evaporation
High energy molecules break loose from surface of fluid

25. Cooling F-E Cooling steam Remove E, Temp E – D condensing
Remove E, no ∆ Temp
Loss of E lets intermolecular forces reform & hold molecules together

26. Cooling D-C Cooling water Remove E, Temp C-B freezing
Remove E, no ∆ Temp
Loss of E strengthens intermolecular forces so molecules can only vibrate