- Internal energy is made up of kinetic energy and potential energy. - An increase in temperature leads to an increase in the kinetic component of the internal energy.
Melting and Solidification - Melting is the change of state from solid to liquid, without a change in temperature. - Thermal energy helps to break the intermolecular bonds between the molecules of the solid. After it is broken, the molecules move out of the positions, and so the solid has melted. - Solidification is the change of the state from liquid to solid, without a change in temperature. - As the intermolecular bonds are formed to change it’s state from liquid t solid, thermal energy is released.
Boiling and Condensation - Boiling is the change of state from a liquid to vapour, occurring at a constant temperature called the boiling point - Condensation is the change of state from vapour to liquid at the same constant temperature. - Thermal energy helps to separate the molecules and also to push back on the surrounding atmosphere. When the molecules are far apart, a change of state from liquid to gas has taken place.
Evaporation - It is a cooling process and it also causes cooling. - Thermal energy is required. - Factors affecting the rate of evaporation: 1. Temperature: The higher the temperature, the higher the rate of evaporation. 2. Humidity of the surrounding air: The higher the humidity, the lower the rate of evaporation. 3. Surface area of the liquid: The larger the exposed area, the higher the rate of evaporation. 4. Movement of air: When the surrounding air is moving, the rate of evaporation will increase. 5. Pressure: The lower the atmospheric pressure, the higher the rate of evaporation. 6. Boiling point of the liquid: The lower the boiling point, the higher the rate of evaporation.
