Carbon is an element with atomic number 6 and atomic mass 12.
Any substance can exist in one of four physical states, solid, liquid, gas and plasma. The temperature of the substance and the pressure under which it has been placed determine which state it exists in.
When carbon is heated and its temperature is raised to 3700 C, it changes state from solid to gas. This is known as sublimation. Most substances that are encountered first change from solid to liquid and then from liquid to gas as they are heated. A few on the other hand, directly change from solid to gas.
The change in state is due to an increase in the energy of the particles that make up the substance. In addition to temperature, pressure has a very important role to play in determining which state the substance is in; at the same temperature a substance can exist in different states dependent on the pressure.