Many metals, like silver, copper, gold and aluminum, are good thermal conductors. Thermal conductors are materials that heat passes through easily. Conduction, or the transfer of heat, can take place within a single material or between two objects.
Heat can only travel from a hot material to a cold material. It does not travel in the opposite direction. Materials that do not pass heat easily are known as thermal insulators. Insulators include plastic, wood, rubber and glass. Often, objects that are used to transfer heat are made of metal but have an insulator as a handle. A saucepan is an example of an object that is both a conductor and an insulator. The metal part of the pan is a conductor that allows heat to quickly pass from the stove to the food inside the pan. The metal part of the pan, however, it is too hot to touch without receiving burns. That is why most handles are made of insulators, such as plastic or wood.
Potholders and oven gloves also function as insulators. Some materials, like glass, operate as insulators at room temperature but as conductors when heated to high temperatures. Gases like air also become more conductive when heated to higher temperatures. Metals, when heated, do not conduct heat as well as they do when cooled. Many conductive materials operate better at very low temperatures.