A calorimeter is a scientific device used to measure the heat transfer associated with chemical reactions, physical changes, or heat capacity. It typically consists of an insulated container that minimizes heat exchange with the environment, allowing for accurate measurements of temperature changes. By calculating the energy changes based on temperature variations, calorimeters help in determining enthalpy, specific heat, and other thermal properties of substances. Common types include bomb calorimeters and coffee cup calorimeters, each suited for specific types of measurements.