1. Thermochemistry
The study of the changes in heat energy that accompany chemical reactions and physical changes

2. Thermochemistry Heat Temperature a form of energy.
can be transferred between samples
heat flows from matter at a higher temperature to matter at a lower temperature
Temperature
a measure of the average kinetic energy of the particles in a sample.

3. Thermochemistry Units of Heat Joule (SI unit) calorie Calorie cal
the amount of energy required to raise the temperature of one gram of water one degree Celsius.
Calorie
Cal
a dietary calorie.
kilocalorie, kcal (1,000 calories)

4. Thermochemistry Enthalpy the heat content of a system represented by H
only changes in enthalpy can be measured
∴ ΔH is used

5. Thermochemistry Specific heat capacity, cp
the amount of energy required to raise the temperature of one gram of a substance one degree Celsius
used in equation
q = m x cp x ΔT

6. Thermochemistry q = m x cp x ΔT
note that in the Metric System, Joules are the unit of measure for heat.
Energy, or heat
(J)
Δ temp
(°C)
mass
(g)
specific heat
(J/g•°C)

7. Heat capacity, cp

8. q = m x cp x ΔT
A 45.0-gram sample of iron is heated from 25.0°C to 50.0°C. How much energy is required? (cp iron = J/g°C)
q = ?
m = 45.0 g
cp = J/g°C
ΔT = 50.0°C – 25.0°C = 25.0°C
q = m cp ΔT
q = 45.0g (0.449 J/g°C) (25.0°C) =
q = 505 J

9. 2. What is the specific heat capacity of an object if a 12
2. What is the specific heat capacity of an object if a 12.5-gram sample is heated from 12.0°C to 28.0°C using joules? q = J m = 12.5 g cp = ? ΔT = 28.0 – 12.0 = 16.0°C q = m cp ΔT