A melting point is the exact temperature at which a solid substance changes into a liquid. Ice has a melting point of 32 degrees Fahrenheit (0 degrees Celsius): below that temperature it stays frozen, above it becomes water. Iron's melting point is much higher, around 2,800 degrees Fahrenheit (about 1,538 degrees Celsius), which is why blacksmiths need extremely hot forges to shape it.

Every pure substance has its own specific melting point. Chocolate melts around 90 degrees Fahrenheit, which is why it softens in your hand. Butter melts at about 95 degrees Fahrenheit. Scientists use melting points to identify unknown substances, since each material melts at a predictable temperature. If you find a mystery metal and measure when it melts, that helps reveal what it is.

The melting point works both ways: when liquid water cools to 32 degrees, it freezes into ice. Scientists call this the freezing point, but it's the same temperature. Think of melting point as the border between solid and liquid, a specific spot on the thermometer where a substance transforms from one state to another.