What is Specific Heat Capacity?
Specific heat capacity is the energy needed to raise 1 kg of a substance by 1°C. It tells us how much each material resists temperature change—water heats slowly, metals heat fast.
Specific heat capacity (c) is the thermal energy required per kilogram per degree: c = Q/(m·ΔT), measured in J/(kg·°C). It's material-specific: water ≈ 4200 J/(kg·°C), aluminum ≈ 900.
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Step-by-step worked examples
100 kJ of heat raises 2 kg of water by 12°C. What is c?
Q = 100,000 J m = 2 kg ΔT = 12°C c = Q/(m·ΔT) = 100,000/(2×12) = 4167 J/(kg·°C)
Aluminum (c = 900 J/kg·°C): how much energy to heat 0.5 kg by 30°C?
Q = c × m × ΔT Q = 900 × 0.5 × 30 = 13,500 J
Lead (c = 130 J/kg·°C) vs water (c = 4200): which needs less energy to heat?
Lead: 130 × 1 × 10 = 1,300 J Water: 4200 × 1 × 10 = 42,000 J Lead needs 32× less energy → much easier to heat
Flashcards
Quick quiz
Q1.50 kJ heats 2 kg by 10°C. Specific heat capacity?
Q2.Unit of c?
Q3.Water vs copper: water heats slower because…
Q4.How much energy to raise 5 kg of iron (c=450) by 20°C?
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Common mistakes
Confusing specific heat capacity (per kg) with heat capacity (total). — Correct: Specific c = heat per kg; total C = heat for entire object.
Thinking higher c means faster heating. — Correct: Higher c means it resists heating → heats *slower*.
Using Fahrenheit in the formula. — Correct: Always use °C or K for ΔT.
Forgetting to multiply by mass. — Correct: Energy Q depends on both c AND m: Q = c·m·ΔT.
FAQ
What is the specific heat capacity formula?
c = Q / (m × ΔT), where Q is thermal energy (J), m is mass (kg), and ΔT is temperature rise (°C).
Why does water have high specific heat?
Hydrogen bonding in water requires lots of energy to break when temperature rises.
Is specific heat capacity constant?
Approximately yes for most problems, though it varies slightly with temperature.
How is specific heat capacity measured experimentally?
Heat a known mass by a measured amount (Q), observe the temperature rise, then calculate c = Q/(m·ΔT).