Why does the color of a metal change by temperature?

All material change colour with temperature. Each colour is associated with a different temperature, independent of the material. This phenomena is know as black body radiation. Radiation occurs because the body is hotter than its surroundings. The energy captured by the body promotes the body's electrons to a higher orbit. When the electrons jump back to a lower orbit, a photon is release. The lower orbits are more desirable (lower potential energy) to the electron and thus it will eventually jump back down. Note: not all photons exist in the visible light region of the electromagnetic spectrum. Thermionic emission is due to the emission of electrons at high temperatures. Thus the difference between thermionic emission and black body radiation is the particle used to transfer the energy. Photons are radiated in black body radiation and electrons are emitted in thermionic emission. Both are ways of transferring energy from a high temperature reservoir to a low temperature reservoir.

Dwayne

Color temperature:

Ask a Scientist: The intensity of the emitted light is a function of the frequency of the radiation and the temperature. So, I guess you might say that an object is emitting all wavelengths, but it only becomes visible when it reaches a certain temperature, the intensity is sufficient to stimulate the retina in your eyes.