1. Thermochemistry
Study of energy changes as matter undergoes physical, chemical or nuclear transformations
Warner – SCH 4U

2. Introduction Many activities involve energy physical changes
melting, boiling,dissolving, etc.
chemical reactions
energy required or used during a reaction
nuclear reactions
nucleus of an atom split (fission) or joined (fusion)

3. What is Energy?
Energy
Kinetic energy (EK)
Potential energy (EP)
Energy due to motion
Energy due to position (stored energy)

4. Systems & Surroundings
In thermodynamics, the world is divided into a system and its surroundings
A system is the part of the world we want to study (e.g. a reaction mixture in a flask)
The surroundings consist of everything else outside the system
SYSTEM
CLOSED
OPEN
ISOLATED

5. OPEN SYSTEM: can exchange both matter and energy with the surroundings (e.g. open reaction flask, rocket engine, you)
CLOSED SYSTEM: can exchange only energy with the surroundings (matter remains fixed) e.g. a sealed reaction flask, terrarium
ISOLATED SYSTEM: can exchange neither energy nor matter with its surroundings (e.g. a thermos flask)

6. THERMAL ENERGY
Total Potential and Kinetic Energy a sample of matter has.

7. Total Energy = Kinetic Energy + Potential Energy
E = EK EP
Kinetic energy & potential energy are interchangeable
Ball thrown upwards slows & loses kinetic energy but gains potential energy
The reverse happens as it falls back to the ground

8. Heating Curve

9. Heating Curve Continued.

10. Temperature
Measure of the average kinetic energy. When K.E increase, motion of particles increases and temperature increase.
Kelvin  Celcius
Celcius  Kelvin
Thermometer used to measure temperature

11. Heat Energy
Energy transformed from one substance to another due to temperature difference between them.
Thermal Energy in Transit
No instrument used to measure heat – must be calculated

12. UNITS OF ENERGY S.I. unit of energy is the joule (J)
Heat and work ( energy in transit) also measured in joules
1 kJ (kilojoule) = 103 J
Calorie (cal): 1 cal is the energy needed to raise the temperature of 1g of water by 1oC
1 cal = J

13. Law of Conservation of Energy
Heat lost by one substance equals heat gained by the other. Energy is not created or destroyed.

14. How to calculate HEAT!! m c t Factor Symbol Mass
Specific Heat Capacity c
Temperature t

15. Specific Heat Capacity
Amount of heat required to raise the temperature of 1 gram of a substance 1oC.
Units: J/goC or J/KgoC
Molar Heat Capacity c x molar mass

16. Calculating Heat Heat (q) is measured in joules (J) q = m c ΔT
q = heat
m = mass (g)
ΔT = change in temp (°C)
c = specific heat capacity (J/g °C)

17. Heat lost/gained when substances are added together.
- q (lost) = + q (gained)
- (mcΔt) = + mcΔt