Which of the following best describes the units of specific heat capacity?

• A. J/(g·K) or J/(kg·K)
• B. J/(mol·K)
• C. J
• D. J/K

Answer: (A)

Specific heat capacity tells you how much energy is needed to raise the temperature of a given amount of material by 1 kelvin. That means the units must express energy per mass per temperature.

The correct units are joules per unit mass per kelvin, i.e., J/(g·K) or J/(kg·K). Those show energy needed per gram (or per kilogram) for each degree of temperature rise.

Other options don’t describe energy per mass per temperature. J/(mol·K) is molar heat capacity—per mole, not per unit mass. J is just energy, not tied to a temperature change per mass. J/K is heat capacity for a whole object (energy per one kelvin change for the entire body), not specific to mass.