👉 Exothermicity is a property of certain substances that occurs when they absorb energy from an external source, such as heat. This process releases heat into the surroundings, which in turn causes the substance to become more dense and increase its volume. In other words, exothermic substances are those that release heat when heated, or have properties that require energy input to change their state. Examples of exothermic substances include many types of materials used in manufacturing and construction, as well as some organic compounds
