In this deck, we'll explore purity, mixtures, and a powerful separation technique called chromatography. You'll learn the chemical definition of a pure substance, how melting points can test for purity, and what formulations are. We'll then cover the required practical for paper chromatography, including how to calculate Rf values to identify substances.

In everyday language, 'pure' might mean natural or clean. But in chemistry, it has a very precise meaning. A pure substance is a single element or a single compound, not mixed with any other substance. For example, pure water contains only water molecules, H two O. Anything else is a mixture. A mixture consists of two or more elements or compounds that are not chemically combined together.

One way to test the purity of a solid substance is to measure its melting point. A pure substance will melt at a specific, sharp temperature. For example, pure ice always melts at exactly zero degrees Celsius. However, if a substance is impure, it will melt over a range of temperatures, and the melting point will be lower than that of the pure substance.