Before we begin, let's think about this situation.
When ice melts. There is a change of phase from solid to liquid. The ice absorbs heat from the surroundings. The heat energy absorbed by the ice does not cause the increase in temperature. The energy absorbed is not transferred to the molecules of ice as kinetic energy.
1. When a substance experiences a change of phase, it absorbs heat energy without a change in temperature. The heat absorbed is known as latent heat.
2. Heat energy needs to be supplied to change a substance from solid to liquid phase and from liquid to gaseous phase.
3. When a solid melts, heat is absorbed but the temperature remains constant.
4. When a a liquid is boiling, heat is also absorbed but the temperature remains constant.
5. From the principle of conservation of energy, we can infer that:
a) latent heat must be given out when a gas condenses to become a liquid and when the liquid solidifies to the solid phase.
b) These two processes also occur at constant temperature.
The four main changes of phase are melting, boiling, condensation and solidification.
Later, we will study the heating curve and cooling curve for a substance. That's all for now
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