The boiling point is the temperature at which a substance converts from liquid phase to gas phase. The melting point, on the other hand, is the temperature at which a substance converts from solid phase to liquid phase. For example, ice (solid water) melts at 0 degrees Celsius and converts to water. Liquid water boils at 100 degrees Celsius and converts to water vapors. Since the chemical composition of the substance stays the same, such as that of water in the above mentioned example, melting and boiling are physical changes. And hence, boiling points and melting points are physical properties. Since they are a property of the material, they can be used to identify it. For example, water is identified with a melting point of 0 degrees Celsius and a boiling point of 100 degrees Celsius.
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