EVERYDAY SCIENCE

Detailed explanation-1: -Pure substances consist of only one kind of matter. All the particles of a pure substance are alike. It has a definite composition and similar properties. This is the reason that pure substances have fixed melting or boiling points.

Detailed explanation-2: -Water has fixed melting and boiling points.

Detailed explanation-3: -Because pure substances have constant properties throughout the whole sample it means that pure substances display a sharp melting point and a sharp boiling point.

Detailed explanation-4: -A pure substance melts at a single temperature, but an impure substance (a mixture) melts over a range of temperatures, and the wider the range of temperatures between where it starts to melt and when it is finished melting, the more impure the substance is.