Because it is difficult to heat solids to temperatures above their melting points, and because pure solids tend to melt over a very small temperature range, melting points are often used to help identify compounds. We can distinguish between the three sugars known as glucose (MP = 150oC), fructose (MP = 103-105oC), and sucrose (MP = 185-186oC), for example, by determining the melting point of a small sample.