Heating & Cooling Graphs (OCR GCSE Physics A (Gateway Science Suite)): Revision Notes

For your exams, you must be able to interpret heating and cooling graphs.

Heating Graph We are going to discuss the heating graph step by step:

1. Solid Heating – as temperature and time increases, the solid is starting to heat up.
2. Melting – once the solid reaches its melting point (in this case it is 0 degrees), it starts to melt and turn into a liquid.
3. Liquid Heating – as temperature and time increases, the liquid is starting to heat up.
4. Boiling – once the liquid reaches its boiling point (in this case, it is 100 degrees), it starts to evaporate and turn into a gas.

Cooling Graph Now, we are going to discuss the cooling graph step by step:

5. Gas cooling – the gas is being cooled down as time goes on.
6. Gas to liquid – once the gas reaches its condensation point, the gas condenses into a liquid.
7. Liquid cooling – the liquid is being cooled down as time goes on.
8. Liquid to solid – once the liquid reaches its freezing point, the liquid freezes into a solid.

The graph shows the temperature of ice:

• At A it is Solid.
• At B, it reaches 0°C.
• From B to C there is no temperature change because the energy is used through melting.
• From C to D it is in liquid state.
• From D to E the water is boiling. This takes longer, because evaporation takes more energy
• From E to F the gas is heating.