MEASUREMENT OF THERMAL ENERGY
Measurement of thermal energy involves indirect measurement of the molecular Kinetic Energy which in total make the heat content (thermal energy) of an object.
FACTORS THAT DETERMINE THE HEAT CONTENT OF A SUBSTANCE
❖ The heat content (thermal energy) of a substance is determined by the following factors.
1) Mass of the substance
2) Temperate change
3) The specific heat capacity of the substance
HEAT CAPACITY OF A SUBSTANCE
Heat capacity (C)
❖ This is the amount of heat required to raise the temperature of a given mass of a substance by one
Kelvin (1K).
CHANGE OF STATE
When matter is heated or cooled it may expand, control or change its state.
These states can be liquids, solids, or gases.
MELTING POINT
➢ Is the change of state from solid to liquid
❖ Melting point takes places at a definite temperature but the temperature does not change until the
pure substance has completed melted.
FREEZING POINT
➢ This is the change of matter from liquid to solid.
❖ At freezing point a liquid changes to solid without change in temperature.
FACTORS AFFECTING THE FREEZING POINT AND MELTING POINT OF A SUBSTANCE
These factors are as follows:
1. Presence of impurities
2. Change in pressure
1. PRESENCE OF IMPURITIES
✓ Impurities such as salt lower both freezing point and melting point of a substance.
2. CHANGE IN PRESSURE
✓ Increase in pressure affects the freezing and melting point of a substance
BOILING POINT
➢ This is the temperature at which all of liquid change into a gas.
❖ At the boiling point, the heat energy supplied is used to change the water from the liquid to vapour
state. It does not raise the temperature.
