The lowest temperature is absolute zero, or negative 273 Celsius. At that point all molecular motion comes to a halt. Heating up an object can cause it to expand, because, the molecules take up more room. When the heat becomes extreme, objects can lose their shape and become a liquid or a gas.

All matter, no matter its form (solid, liquid, gas) is made up of molecules. No matter what, these molecules are moving around and are active. Moving atoms or molecules are called internal energy. Internal energy's formal definition is "the total kinetic and potential energy associated with the motions and relative positions of the molecules of an object, excluding the kinetic or potential energy of the object as a whole. An increase in internal energy results in a rise in temperature or a change in phase." (definition from dictionary.com) We can then assume that if the temperature of matter has risen, there has been an increase in its internal energy. If its temperature has lowered, its internal energy has lowered as well.

Heat is likely to exchange between matter. This process of exchanging heat is called heat transfer. It is important to note that "heat transfer occurs from warm to cool." This transfer occurs generally in one of three ways: conduction, convection, or radiation. Each is as important as the next.

Conduction deals with the transfer of heat in matter in its solid state. When part of solid matter is heated, "electrons become excited." Molecules then collide and heat it up when they pass objects. Heat can also be transferred within the same object. This process is known as thermal conductivity. Objects with a high level of thermal conductivity are usually good conductors of electricity. One good example is gold. Objects with a low level of thermal conductivity are usually nonconductors. Nonconductors of electricity are typically good insulators.

Convection follows a very similar process to conduction, with one exception; the state of matter is that of liquid or gas. When the liquid or gaseous matter is heated, the more active molecules move upward and the more latent molecules hover toward the bottom. Ever wonder why cool air is initiated to circulate throughout your house toward the ceiling, while heated air begins its route toward the floor? This allows the air to mix properly, giving a more even temperature throughout the house. Cool, huh!

Finally, there is radiation. Radiation is quite different from conduction and convection, as it does not rely on the "presence of matter". Radiation is "energy radiated or transmitted in the form of rays, waves, or particles." Due to the sun's intense heat, it releases a great deal of radiant energy.