3.2.6Particle Model of Matter
Specific Heat Capacity v Specific Latent Heat
5 min read 6 parts Lesson 11 of 14 Unit quiz
Section 1 of 6Two ideas, two equations
| Feature | Specific heat capacity (c) | Specific latent heat (L) |
|---|---|---|
| Meaning | Energy to raise 1 kg by 1 °C | Energy to change the state of 1 kg |
| Equation | ΔE = m × c × Δθ | E = m × L |
| Unit | J/kg °C | J/kg |
| Temperature | Changes | Stays constant |
| Where energy goes | Kinetic energy of the particles | Potential energy of the particles |
| On a heating graph | The sloping sections | The flat sections |
Section 2 of 6Which equation should I use?
1
Read the question for a temperature change: if the substance warms or cools within a single state, use ΔE = m × c × Δθ.
2
If the question says melts, boils, freezes or condenses at a stated temperature, use E = m × L.
3
If both happen, split the problem into stages and calculate the energy for each stage separately.
4
Add the stages together to get the total energy.
Section 3 of 6Example with two stages
1Warm the ice
- Warm the ice Use ΔE = m × c × Δθ with the specific heat capacity of ice.
2Melt the ice
- Melt the ice Use E = m × L with the latent heat of fusion at 0 °C.
3Warm the water
- Warm the water Use ΔE = m × c × Δθ with the specific heat capacity of water.
4Total
- Total Add the three energy values for the energy supplied overall.
Section 4 of 6Particle explanations
Heat capacity
- Heat capacity Energy supplied makes particles vibrate or move faster, so the temperature rises.
Latent heat
- Latent heat Energy supplied overcomes the attraction between particles, increasing potential energy while temperature stays the same.
Size comparison
- Size comparison For water, L for boiling (2 260 000 J/kg) is much larger than the energy to warm 1 kg by 1 °C (4200 J/kg °C),
- because particles must be separated completely.
Section 5 of 6Key terms
| Term | Meaning |
|---|---|
| Specific heat capacity | Energy needed to raise the temperature of 1 kg of a substance by 1 °C. |
| Specific latent heat | Energy needed to change the state of 1 kg of a substance without a temperature change. |
| Temperature change | The difference between the final and starting temperatures, in °C. |
| Kinetic energy | Energy of motion. |
| Potential energy | Energy stored due to the arrangement of the particles and the forces between them. |
Section 6 of 6Exam technique
1
Using E = m × L during a temperature rise, or ΔE = m × c × Δθ during a state change.
2
Forgetting to include every stage when a substance warms, melts and then warms again.
3
Mixing up the unitsc is J/kg °C but L is just J/kg.
4
Saying specific latent heat is the energy needed per degree; there is no temperature in it.