Merry Van Dam, age 11, of Escondido, Calif., for her question:

How hot must iron be before it melts?

Pots and pans, pokers and barbeque grills made of iron are frozen solid. At ordinary everyday temperatures, all iron is in the solid state, just as water becomes solid ice when the temperature drops to 0 degrees centigrade. Iron melts or freezes solid at a temperature of 1,533 degrees Centigrade. This is the temperature at which we can expect it to change from its solid, frozen state to its runny liquid state, or vice versa.

The freezing point of a substance is the same as its melting point. At 1,533 degrees centigrade, solid iron begins to melt and liquid iron begins to freeze. If we heat a pan of liquid water, it boils and changes to steamy gas. This happens when the water reaches 100 degrees C., which is its boiling point. Iron also has a boiling point at which the runny liquid changes to gas. The boiling point of iron is around 3,000 degrees C.