Heat questions sort into three situations: a temperature change, a change of state, and a gas under changing conditions. Naming the situation first tells you which formula to use.
This section is part of SPM Physics. The units and significant figure checker helps with the conversions that heat calculations need.
How do the parts connect?
Study the lessons in this order.
- Thermal equilibrium explains why heat flows from hot to cold and when it stops.
- Specific heat capacity calculates the energy for a temperature change.
- Specific latent heat calculates the energy for melting or boiling.
- The gas laws relate pressure, volume and temperature of a fixed mass of gas.
- Temperature-time graphs show all of the above in one picture.
Each step builds on the earlier ones, so a weak first step weakens the graph lesson.
One short example
How much energy heats 0.20 kg of water from 20°C to 70°C? Use c = 4200 J kg⁻¹ °C⁻¹. The temperature changes by 50°C, so Q = mcθ = 0.20 × 4200 × 50 = 42 000 J.
Now suppose the water then boils at 100°C. The temperature stops rising, so Q = ml takes over. One question, two formulas, chosen by asking what happens to the temperature.
Who should start where?
Choose by the question type that trips you up.
| Your difficulty | Start with |
|---|---|
| Explaining why heat flows | explaining thermal equilibrium |
| Temperature-change energy | using specific heat capacity |
| Melting and boiling energy | using specific latent heat |
| Gas pressure, volume, temperature | applying gas laws under stated conditions |
| Heating curves | interpreting temperature-time graphs |
When each feels steady, mix them in the heat practice set.
To have a teacher sort the formulas with you using your own questions, see online one-to-one Physics tuition.