# What is the Difference between Heat an Temperature

Heat is a form of energy associated with temperature and is more correctly termed thermal energy. In fact the term heat is used to describe the transfer of thermal energy from one substance to another. For example, the end product of a radiator is the production of thermal energy, however, when that energy is transferred from the radiator to the surrounding environment, it is felt as heat or indirectly measured as a change in temperature.

So what is heat? And what are the properties of heat?

Essentially, heat is the total amount of the kinetic energy produced by the random vibrating motion of molecules and atoms within substances and the measured temperature is the amount of energy per molecule. This relatively straight forward distinction between heat and temperature makes it easier to see that the more particles on object has, the more heat or thermal energy it contains but that doesn’t necessarily mean it has a higher temperature. So the more vibration or kinetic energy particle have, the more heat there is. The less kinetic energy there is, the less the particles will vibrate.

Incidentally, this also goes some way to explaining why substances expand and contract when heated up or cooled down. Depending on the substance in question, the vibration can be so great that individual particles begin to escape and this is what takes place during evaporation or boiling of a liquid for example. In general, the forces that hold molecules together in solids are stronger than in liquids so require a lot more heat for them to escape, instead they separate taking up more space but still remain bound toegther. The forces between gas molecules are much weaker and therefore require much less heat to exist in this liberated state.

Since heat is thermal energy, that energy can be transferred, however, one of the properties of heat is that it always flows from hot to cold until it reaches a state of equilibrium. For example, the heat from a hot drink transfers into the cup in which it is held and into the surrounding environment until the temperature of the drink and the cup are the same as the environment. The hotter drink cools down and the cooler environment becomes slightly warmer. Although the room itself has some heat, it is not the case that the heat from the room would transfer to hotter drink making it even hotter.

Heat energy itself can be transferred via three basic modes.

Conduction.
This is the transfer of heat energy by direct contact of substances. An example of this is placing a saucepan of hot water on a hot electric plate. The heat from the plate transfers directly from the plate to the saucepan.

Convection.
This is the transfer of heat energy by diffusion or circulation of heated particles. Taking the saucepan example, the water molecules at the bottom of the pan would become hot and rise to the surface, the cool water molecules sink and become heated as they get closer to the heat source. This type of heat transfer also takes place in gases such as air in convection heaters where the air is warmed and circulated in a room.