1. Heat capacity and Calorimetry
Thermochemistry II
Heat capacity and Calorimetry

2. Calorie A calorie is a unit of heat.
It is defined as the quantity of heat (q) needed to raise one gram of pure water one degree C.

3. calorie versus Calorie
Dietary units of energy are Calories.
1000 calories =
1 kilocalorie =
1 Calorie

4. Joules Joule is the SI unit for energy. 1 joule= 0.2390 cal 1 cal =

5. Heat Capacity
The amount of heat needed to increase the temperature of an object exactly 1 degree C is the heat capacity of an object.
Different objects have different heat capacities.
Which heats faster, Cu or Al?

6. Heat Capacity

7. Specific heat capacity
Specific heat capacity or Specific Heat, is the amount of heat it takes to heat 1 gram of a substance 1 degree C.

10. Examples
If a chunk of silver has a heat capacity of 42.8 J/°C. If the silver has a mass of 181 grams, calculate the specific heat of silver.
Answer:
0.236 J/(g °C)

11. Calorimetry

12. Enthalpy ∆H is the heat under constant pressure.
What pressure is constant?
Atmospheric Pressure.

13. q= ∆H = m x C x ∆T ∆H is the heat under constant pressure.
C is the heat capacity.
In calorimetry, C is the heat capacity of water, the item heated.(system or surrounding?)
∆T is the change in temperature.
T final – T initial = ∆T

14. Bomb Calorimetry

15. ∆H versus q In a bomb calorimeter, the pressure is not constant.
With combustion under a constant volume, pressure will increase.
Therefore we must use q and not ∆H.

16. Example:
Go to worksheet.