Heat has more or less influence in changing these properties in a given material.

Hardness and strength are increased by hammering or rolling a metal, and these properties are changed, often in a marked degree, by a slight amount of another substance in the metal.

Conductivity is usually increased or decreased by heat, and electric conductivity is greatly reduced by impurity in metals.

Some metals and alloys expand upon cooling, due to certain ingredients.

Heating and cooling suddenly, will render steel hard and brittle, and annealing, which is a different process for different metals, brings a metal or an alloy back to its natural or normal state of softness after having been hardened by hammering, rolling, or otherwise.