Why does iron go red when heated?
Iron goes red when heated because its atoms radiate vibratory waves of an electromagnetic nature that are visible as light as a sufficiently high temperature. At 8000 C the iron is at low-red heat. But as the heat increases the iron will turn bright red, and finally white-hot and molten.
Heat is passed through the iron by conduction-the contact of one iron particle with another with no dependence on particle movement. The heat which is given off as light when iron glows red-hot can be reconverted into heat by the substance on to which it falls. When iron is heated to a temperature below 3000 C it gives off invisible rays of infra-red radiation which are similar in nature to light. But they do not contain quite enough energy per unit (photon) to stimulate the optic nerve and do be seen by the human eye.
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