What is specific heat capacity?

Specific heat capacity, Cp, is the energy needed to raise the temperature of one kilogram of a substance by one kelvin at constant pressure. It is measured in J/(kg·K). Water has a notably high Cp of about 4186 J/kg·K, which is why it stores and releases heat slowly.

How do I calculate heat energy from Cp?

Use Q = m × Cp × ΔT, where m is mass in kilograms, Cp the specific heat, and ΔT the temperature change in kelvin. Heating 2 kg of water by 30 K needs 2 × 4186 × 30 ≈ 251 kJ. The same temperature rise in 2 kg of copper needs only about 23 kJ.

Why is water's specific heat so high?

Water molecules form an extensive hydrogen-bond network. Adding heat must break and rearrange these bonds before raising kinetic energy, so a great deal of energy goes in per degree. This high heat capacity moderates climate and makes water an excellent coolant.

What is the difference between Cp and Cv?

Cp is the heat capacity at constant pressure, where the substance may expand and do work; Cv is at constant volume. For solids and liquids the two are nearly equal, but for gases Cp is noticeably larger because expanding gas does work on its surroundings.

Does specific heat depend on temperature?

Yes, modestly. The values here are representative figures near 25°C. Over wide temperature ranges, or near phase changes, Cp shifts and a temperature-dependent value or enthalpy table should be used for accurate work.

Specific Heat Capacity Reference

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Specific heat capacity tells you how much energy a substance soaks up per degree of temperature rise. This reference lists Cp, in joules per kilogram-kelvin, for more than fifty solids, liquids, and gases near room temperature, searchable by name and filterable by phase.

How it works

Specific heat capacity at constant pressure, Cp, links heat to temperature through Q = m · Cp · ΔT. Here Q is the heat added in joules, m the mass in kilograms, and ΔT the temperature change in kelvin (the same size as a degree Celsius). Rearranging, Cp = Q / (m · ΔT), so the units are J/(kg·K). A high Cp means a substance needs a lot of energy to warm up and gives a lot back as it cools — it has high thermal mass.

Why values differ so widely

Lightweight molecules with many ways to store energy have high Cp. Hydrogen gas tops the table at about 14300 J/kg·K because its tiny molecules pack many modes of motion per kilogram. Water is unusually high for a liquid because its hydrogen bonds absorb energy. Dense metals like gold and lead sit near the bottom, around 130 J/kg·K, since each kilogram contains relatively few, heavy atoms.

Example and notes

To heat a 150 L (150 kg) hot-water tank from 15°C to 60°C needs 150 × 4186 × 45 ≈ 28.3 MJ, about 7.85 kWh — which is why water heating dominates household energy. The same energy would raise an equal mass of copper by over 490 K. Values here are at constant pressure near 25°C; for gases note that Cp exceeds Cv, and for any substance Cp drifts with temperature, so use enthalpy tables for precise wide-range work.