1. Heating and Cooling Curves

2. Heat vs Temperature
Heat is the total molecular energy (kinetic and potential); measured in Joules (J)
dependent on # particles present
Temperature is a measure of kinetic energy of molecules; measured in Celsius
NOT dependent on the particles
If heat is added, temperature will increase

3. Heat is used in 2 ways Change temperature
heat added: KE increase; molecules speed up
heat removed: KE decrease; molecules slow
Change state/phase
heat added: PE increase; IMFs weaken
heat removed: PE decrease; IMFs strengthen

4. IMFs
Intermolecular Force = “The Force” that holds solids and liquids together.

5. Phase Changes
Gas
Liquid
Solid

6. Melting and Freezing Points
Freezing Point = the temperature when a liquid turns to a solid
Melting Point = the temperature when a solid turns to liquid
REVERSIBLE processes...therefore mp = fp
For water : 0 degrees Celsius

7. Heating Curve
Heat Added ---->
Temperature (o C) 1 2 3 4 5

8. Segment 1 Solid No phase change; solid increases in temp
Molecules are moving faster
Potential Energy: No Change
Kinetic Energy: Increase

9. Segment 2 Solid and Liquid Melting; no temp change
IMFs are being broken
Potential Energy: Increase
Kinetic Energy: No Change

10. Segment 3 Liquid No phase change; liquid increases in temp
Molecules are moving faster
Potential Energy: No Change
Kinetic Energy: Increase

11. Segment 4 Liquid and Gas Boiling; no temp change IMFs are being broken
Potential Energy: Increase
Kinetic Energy: No Change

12. Segment 5 Gas No phase change; gas increases in temp
Molecules are moving faster
Potential Energy: No Change
Kinetic Energy: Increase

13. Cooling Curve 1 2
Temperature (o C) 3 4 5
Heat Removed --->

14. Segment 1 Gas No phase change; gas decreases in temp
Molecules are moving slower
Potential Energy: no change
Kinetic Energy: decreases

15. Segment 2 Gas and Liquid Condensing, no temperature change
IMFs are being restored
Potential Energy: Decreases
Kinetic Energy: No Change

16. Segment 3 Liquid No phase change; liquid decreases in temp
Molecules are moving slower
Potential Energy: no change
Kinetic Energy: decreases

17. Segment 4 Liquid and Solid Freezing; no temperature change
IMFs are being restored
Potential Energy: Decreases
Kinetic Energy: No Change

18. Segment 5 Solid No phase change; solid decreases in temp
Molecules are moving slower
Potential Energy: No change
Kinetic Energy: Decreases

19. Vaporization and Boiling Point
Vaporization: liquid → gas
Evaporation occurs without heat
Boiling occurs when the vapor pressure and the atmospheric pressure are equal.
Boiling Point the temperature at which a liquid boils at standard pressure (1 atm)

20. Calculating Heat for Temperature Change
Q = mC∆T
Q = Heat Lost (-) or Heat Gained (+) in Joules (J)
m = mass (g)
C = Specific Heat Capacity (J/goC)
∆T = Change in Temperature (oC) = Tfinal - Tinitial

21. Calculating Heat for Phase Change
Q melt/freeze = mLfusion
Qboil/condense = mLvaporization
Q = Heat Lost (-) or Heat Gained (+) in Joules (J)
m = mass (g)
L = Latent Heat (J/g)