This heat exchange may occur due to physical changes, chemical reactions, or even sudden phase changes in the object or systems being observed. The energy change attribution can vary.

This type of measurement is able to determine if a chemical reaction resulted in the loss or absorbance of heat, referred to as exothermic reactions or endothermic reactions, respectively.

A calorimeter, which applies calorimetry to measure the amount of heat energy that is either lost or gained during some chemical or physical process, is a ubiquitous lab instrument found across several varying industries.

Calorimeters are used to find the amount of heat required to raise the temperature of a system or object by one degree. This is known as finding a system’s heat capacity, and is expressed as joules per kelvin (J/K). When heat capacity is expressed in calories per gram, this is referred to as specific heat.

Calorimeters can also be used to determine entropy and enthalpy. Entropy measures how much energy is spread out in a process over time or how spread out the initial energy of a system becomes at constant temperature. Enthalpy, on the other hand, relates to entropy in that entropy is roughly the heat supplied—or change in enthalpy—divided by temperature.

In its most basic form, a calorimeter is an enclosed, well-insulated chamber, filled with a known reference material that can measure the heat of reaction inside the chamber. Water is often used because most of the important properties of it are already known.