1. Thermochemistry

2. Thermochemistry
All changes in matter, both physical and chemical, involve changes in energy
Thermochemistry is the study of energy changes is physical and chemical processes

3. Energy All forms of energy can be classified as either:
Kinetic Energy - energy of motion
Potential Energy - stored energy
SI unit = joule (J) = kg·m2/s2
1 J is approximately the amount of energy required to lift an apple 1 m (very small!) so often expressed as kJ (1000 J)
1 calorie = J

4. System & Surroundings
System: substances in which a change (physical or chemical) occurs e.g. reactants and products
Surroundings: Everything else in the universe! Usually only consider anything nearby that is capable of exchanging energy or matter

6. Endothermic & Exothermic
Endothermic Processes:
Heat is absorbed by the system from the surroundings
Feels cold
Exothermic Processes:
Heat is released from the system into the surroundings
Feels hot

7. Energy, Temperature & Heat
Thermal Energy: The sum of all kinetic energies of all the particles in a system. Cannot be measured.
Temperature: A measure of the average kinetic energy of all the particles in a system. Can be measured.
Heat: Kinetic energy transferred between substances. I.e. an object cannot possess heat.

8. Heat Capacity
Heat Capacity: Amount of heat required to raise the temperature of a substance of any mass by 1˚C.
C = J/˚C
Specific Heat Capacity: Amount of heat required to raise the temperature 1 g of a substance by 1˚C.
c = J/g•˚C
You are provided with a glass of milk and a swimming pool of milk.
Which will have the higher heat capacity?
Which will have the higher specific heat capacity?
Molar Heat Capacity: Amount of heat required to raise the temperature 1 mole of a substance by 1˚C. c = J/mol•˚C

10. Factors that Affect Heat
Mass - the greater the number of particles, the more heat required
Type of Substance - each substance has a different specific heat capacity
Temperature Change - the greater the temperature change the more heat required
Q = mc∆T

11. Calculating Heat
When a 1.25 kg sample of water was heated in a kettle, its temperature increased from 16.4˚C to 98.9˚C. How much heat did the water absorb?
Q = mc∆T
Q = ?
m = 1.25 kg
c = 4.18 J/g•˚C
∆T = T2 - T1
= 98.9˚C ˚C
= 82.5˚C

12. Practice
p. 300 #1-5
p. 302 #8-13
p. 305 #1-6
Specific Heat Capacity Worksheet