1. Warm Up: Get out Reaction Diagram Paper
Today: MORE NOTES! 
Learning Targets:
I can calculate the heat needed to run phase changes
I can determine the specific heat of unknown
substances
Homework: Calorimetry Practice (back of notes)

2. Radiant
Mechanical
Electric
Nuclear
Chemical
Sound
Thermal
Elastic
Magnetic

3. The Role of Heat in Chemistry

4. Units of Energy
calorie (cal) = the amount of energy it takes to raise 1 g of water by 1ºC Calorie (Cal) = 1000 calories Joule (J) = metric (SI) unit for energy 1 cal = J Kilojoule (kJ) = 1000 Joules

6. Enthalpy (H)
286 kJ/mole
How much heat energy an object contains (measured in kilojoules per mole)
236 kJ/mole
242 kJ/mole

7. Enthalpy (H) 286 kJ - 242 kJ = + 44 kJ
286 kJ/mole
how much energy will be transferred when a mole of water changes to a mole of steam?
236 kJ/mole
286 kJ -
242 kJ
= kJ
242 kJ/mole
(heat must go in)

8. Enthalpy (H) 472 kJ - 572 kJ = - 100 kJ
286 kJ/mole
how much energy will be transferred when two moles of steam changes to two moles of ice?
236 kJ/mole
472 kJ -
572 kJ
= kJ
242 kJ/mole
(heat must go out)

9. energy in = + ΔH energy out = - ΔH
endothermic
exothermic

10. Entropy
Entropy is a measure of randomness or disorder.

11. Is Entropy Increasing or Decreasing?
Leaving a hot cup of coffee out on the desk
Leaving an ice cube out on the desk
A lake freezing over in the winter
Burning gasoline to make your car run
Cutting a piece of paper into confetti
Cleaning your room

12. System is getting more ORDERED, so entropy decreases
Entropy in Chemistry
In the following equation, is entropy increasing or decreasing?
2 H2 (g) + O2 (g)
2 H2O (l)
3 moles of GAS
2 moles of LIQUID
System is getting more ORDERED, so entropy decreases

13. (+) (-) Enthalpy (ΔH) Entropy Conclusions Endothermic Exothermic
Increasing disorder
Decreasing disorder
(more order)

14. Calorimeters
Heat = mΔTCp or q

15. Ex. #1:
When MgSO4 dissolves in 15.0 mL of water (d = 1.00 g/mL) at 25°C, 1.51 kJ of heat is evolved
Is the process endothermic or exothermic?
Write a balanced equation
What is qH2O?
What is the final temperature of the solution? (cp of H2O = 4.18J/g°C)

16. Ex. #3:
Burning 1.00mL of isooctane (d = 0.688g/mL) releases 33.0 kJ of heat.
When 10.0 mL of isooctane is burned in a bomb calorimeter, the temperature in the bomb rises from 23.2°C to 66.5°C. What is the heat capacity of the calorimeter?

17. Calculating heat for physical changes
boiling point
melting point

18. Heat of fusion/vaporization
The heat involved in changing state of matter
DHfus = Heat of fusion
heat required to melt/freeze 1 mole or 1 gram of a substance
DHvap = heat of vaporization
heat required to evaporate/condense a 1 mole or 1 gram of a substance
Positive if warming
Negative if cooling

19. Using heating curves For warming/cooling, q = mc∆T
m = mass
cp = specific heat capacity
∆T = change in temp (negative if cooling, positive if warming
For phase change, q = (m or n)DHfus or
q = (m or n)DHvap
n = moles
Hfus = Heat of fusion
Hvap = heat of vaporization
You will choose mass or moles based on units given for DHfus/DHvap

21. Ex. #2:
Calculate the amount of heat involved in changing 10.0 g of liquid Br2 at 22.5°C to vapor at 59.0°C.
m.p. = -7ºC DHfus = 10.8 kJ/mol
b.p. = 59ºC DHvap = 29.6 kJ/mol
Cp = J/gºC