By Claire Gillespie
Updated Aug 30, 2022
Анатолий Тушенцов/iStock/GettyImages
A calorimeter may sound like a high‑tech gadget, but it’s a straightforward heat‑measurement device that can be built at home with two coffee cups. Frequently used in school science projects, it quantifies the energy exchanged in chemical or physical processes, such as heat transfer or a substance’s specific heat.
Heat causes a liquid’s temperature to rise or fall. By recording the liquid’s mass and the resulting temperature change, a calorimeter calculates the energy gained or lost.
A basic calorimeter consists of two vessels: an outer container and a nested inner vessel. The air (or foam) between them acts as a thermal insulator, preventing heat exchange with the external environment. Lab‑grade calorimeters often feature a fiber ring that keeps the inner vessel centered, a thermometer to track temperature, and a stirrer to distribute heat evenly. A homemade “coffee‑cup” version is simpler but less accurate due to greater heat loss to surroundings.
When an exothermic reaction releases energy, the solution’s temperature rises; an endothermic reaction absorbs energy, causing the temperature to drop. By measuring the temperature shift along with the solution’s specific heat and mass, you can compute the reaction’s heat change. For instance, inserting a hot copper rod into cold water in a calorimeter causes heat to flow from the copper to the water until both reach the same temperature (thermal equilibrium). No heat leaves the system, so all transfer occurs internally.
Specific heat is the amount of energy needed to raise 1 g of a substance by 1 °C. It varies among materials—for example, water’s specific heat is 1.00 cal/g·°C. To determine an unknown metal’s specific heat, heat the metal, then immerse it in water inside the inner vessel. Record the final equilibrium temperature. Calculate the heat absorbed by the water (mass × specific heat × ΔT) and the heat lost by the metal (mass × ΔT). Dividing the water’s heat by the metal’s gives the metal’s specific heat.
