Cambridge O Level Physics · Syllabus 5054 · Thermal Physics
Specific Heat Capacity
What is Specific Heat Capacity?
Specific heat capacity is the energy required per unit mass per unit temperature increase, given by c = change in energy divided by mass times change in temperature, and measured in joules per kilogram per degree Celsius or equivalently joules per kilogram per kelvin.
This definition is part of the Thermal Physics chapter in Cambridge O Level Physics.
Specific Heat Capacity in context
Heating a substance normally increases the average separation of its particles, so the substance expands — most for gases, less for liquids, least for solids. The energy needed to raise the temperature of one kilogram of a substance by one degree is its specific heat capacity, \(c = \Delta E/(m\,\Delta\theta)\). When a pure substance melts or boils, the energy supplied separates particles against the forces between them instead of speeding them up, so the temperature stays constant during the change; that energy is the latent heat. Evaporation is different again: it happens only at the surface, at any temperature, and it cools the liquid left behind.
Questions students ask about Specific Heat Capacity
How do you set out a specific heat capacity calculation in the exam?
Specific heat capacity \(c\) is the energy required per unit mass per unit temperature increase, \(c = \Delta E/(m\,\Delta\theta)\). Substitute the mass in kilograms and the temperature change in degrees Celsius — or kelvin, since a change of 1 °C equals a change of 1 K — then rearrange for whichever quantity is missing. Always check which value belongs in the denominator before substituting.