1. Enthalpy

2. Specific Heat Capacity Definition: The HEAT ENERGY required to raise the TEMPERATURE of 1kg of substance by 1 o C. e.g. for water C= 4.18kJ kg -1 o C -1 N.B. C changes for every liquid

3. Measuring Heat Energy Energy is measured in Joules (J): 1 kilojoule (kJ) = 1000 joules 4.18 kJ of energy is required to raise the temperature of 1kg of water by 1 o C. To calculate the amount of heat energy needed to raise the temperature of a KNOWN VOLUME of water we use the equation:

4. EH = c x m x ΔT EH = heat energy (kJ) c = specific heat capacity of water m = mass of water (kg) ΔT = change in temperature ( o C)

5. Example Q. A kettle contains 500cm 3 of water at a temperature of 20 o C. How much energy must be supplied to boil the water? A. EH = c x m x ΔT m= 500cm 3 =500g=0.5kg = 4.18 x 0.5 x 80 ΔT= 100-20= 80 o C = 167.2kJ

6. Example Q. A Bunsen burning for 1 minute heated 100cm 3 of water from 25 o C to 75 o C. Calculate the heat energy produced by the Bunsen. EH = c x m x ΔT m= 100cm 3 =100g=0.1kg = 4.18 x 0.1 x 50 ΔT= 75-25= 50 o C = 20.9kJ