1. Melting

Change of state from solid to liquid, without a change in temperature.

During melting, temperature remains constant at the melting point. Thermal energy is absorbed by the substance.

2. Solidification

Change of state from liquid to solid, witjout a change in temoerature.

During solidification, the temperature remails constant at the freezing point. Thermal energy is released by the substance.

3. Boiling

Change of state from liquid into vapour (gas), happening at a constant temperature; boiling point.

During boiling, the temperature remains constant at its boiling point. Thermal energy is absorbed by the substance.

4. Condensation

The process where vapour (gas) changes into liquid at a constant temperature. Heat is given out during the process.

During condensation, the temperature remains constant at the condenstion point. Thermal energy is released by the substance.

5. Evapouration

A cooling process

Evapouration of a liquid is due to molecules at the surface with energy greater then the average kinetic energy escaping from the rest of the liquid.

• Internal Energy is made up of (the sum of) Kinetic energy & Potential energy
• An increase in temperature leads to an increase in the Kinetic Component of the Internal Energy.

8.3 Radiation

1. Continual emission of infrared waves from the surface of all bodies, transmitted without the aid of a medium

2. Infrared radiation is absored by all surfaces, hence causing temperature to rise.

2. Occur only in fluids but not in solids.
- because convection involves the BULK movement of the fluids which carry thermal energy with them.

- Thermal energy in solid is transferred from one particle to another through vibrations without any bulk movement of particle themselves.

1. Thermal energy flows through the material of each rod without any flow of the material itself.


2. Different materials conduct heat at different rates.

• Random or irregular motion of smoke particle in air/ pollen grains in water.
• When temperature increases, the smoke particles are observed to move faster and more vigorously.
• caused by the bombardedment of air molecules on smoke particles/ water molecules on pollen grains in water

Vibrate about Fixed Position,

held in position by Strong Intermolecular Bonds.

(Fixed Volume & Shapes)