Gas test

A gas test pairs a particular action with a characteristic observation. For example, you must say not only that you used a splint, but whether it was lighted or glowing, and what happened to it.

A gas is often colourless, so looking at it is not enough to identify it. Instead, carry out a gas test: expose the gas to a particular substance and look for a characteristic positive result. A complete description must state both the procedure and the observation.