the properties of something can be used to identify that something & a substances boiling point is a kind of physical property ->  a substance 's boiling point can be used to identify the substance  a substance 's boiling point can be used to identify the substance & water is a kind of substance ->  the boiling point of water can be used to identify water  the boiling point of water can be used to identify water & water is a kind of substance & the boiling point of water is 100c -> if a substance has a boiling point of 100c, then that substance is water