1989 - JAMB Chemistry Past Questions and Answers - page 1

A mixture is a substance that contains two or more components that are not chemically bonded. One way to identify a mixture is by its melting behavior. A pure substance has a sharp, distinct melting point, while a mixture usually has a melting range, meaning it melts over a range of temperatures.

• A. Grinding a solid to a fine powder is a physical change that could happen to either a pure substance or a mixture.
• B. Density is a physical property that can be associated with both pure substances and mixtures.
• C. A melting range (300°C to 375°C) indicates that the solid melts over a range of temperatures. This is characteristic of a mixture, not a pure substance.
• D. Absorbing moisture from the atmosphere