Specific heat capacity

The specific heat capacity c of a substance is the heat needed to raise one unit of its mass by one degree of temperature, so that Q = m c ΔT. It quantifies how much a material resists changing temperature when heat is added: a large c means a large heat input produces only a small temperature rise.

Values vary enormously. Liquid water's specific heat, about 4.186 J/(g·K), is anomalously high — a consequence of its hydrogen-bond network, which stores energy in flexing and breaking bonds as well as in molecular motion. Metals are far lower: copper about 0.385, lead about 0.13 J/(g·K). This is why oceans moderate climate, why a cast-iron skillet heats quickly, and why a pound of water and a pound of mercury given equal heat reach very different temperatures.

Specific heat is measured by calorimetry — typically the method of mixtures — and it splits into constant-volume and constant-pressure versions for gases. The per-mole counterpart, the molar heat capacity, exposes the deeper regularity captured by the Dulong–Petit law and equipartition.

Discovered and named by Joseph Black in the 1760s, who recognised that substances differ in their 'capacity' for heat; refined throughout the nineteenth century and explained microscopically by kinetic theory and quantum statistics.