Physics · Both
Specific Heat Capacity & Latent Heat
Calculating energy changes using specific heat capacity and latent heat; linking to insulation.
Different materials need different amounts of energy to change temperature. Specific heat capacity quantifies this; latent heat is about changes of state.
Specific heat capacity
Energy to change temperature:
ΔE = m c Δθ
• ΔE – energy (J)
• m – mass (kg)
• c – specific heat capacity (J/kg°C)
• Δθ – temperature change (°C)
Materials with high c (e.g. water) heat up and cool down slowly.
Worked example
How much energy to heat 2 kg of water by 10°C? (c = 4200 J/kg°C)
Solution
ΔE = 2 × 4200 × 10 = **84 000 J**
Latent heat
Energy to change state **without** temperature change:
E = m L
L = specific latent heat (J/kg)
• Fusion – solid ↔ liquid
• Vaporisation – liquid ↔ gas
Reducing heat loss
Insulation, double glazing, loft insulation, cavity walls reduce energy transfer by conduction, convection and radiation – saves energy in homes.
Practice questions
Try these without looking at the answers first.
Q1.Formula for specific heat capacity energy?
Show answer
ΔE = m c Δθ
Q2.What does latent heat change?
Show answer
State (not temperature)
Q3.Energy to heat 0.5 kg by 4°C if c = 1000?
Show answer
2000 J