In this deck, we'll explore how chemists identify unknown ions in a solution. This is a key part of chemical analysis and a required practical for your GCSE. We'll learn a series of chemical tests that produce distinctive results, often forming a solid called a precipitate, which can tell us which ions are present.

First, let's look at how to identify positive metal ions, also known as cations. A common method is to add a few drops of sodium hydroxide solution. Many metal ions react with hydroxide ions to form insoluble precipitates of a specific colour.

If you add sodium hydroxide solution and a blue precipitate forms, this indicates the presence of copper two ions. The precipitate is copper two hydroxide.