Heat is a concept from the realm of physics that represents a form of energy, with thermal energy moving between atomic particles. The word heat can also refer to something hot, that is, with high temperature.
The greater the heat (thermal energy) applied to an object or system that is in isolated conditions (without external influences), the higher its temperature. When two bodies have different temperatures and are in contact, heat passes from the object with higher temperature to the lower temperature, until thermal equilibrium is reached.
Although many times the unit of measurement of heat is caloric (cal), according to the International System, heat is measured in joule (J), in honor of James Prescott Joule, British physicist who discovered (along with other physicists ) That mechanical energy could turn into heat and vice versa.
