Grade 12 students are engrossed in a titration activity to find the unknown concentration of a sodium hydroxide solution using a solution of oxalic acid of known concentration. The basic solution starts off being bright pink because of the phenolphthalein indicator. As the acid is added the mixture loses it colour - the challenge is to stop adding acid before the last drop when the colour disappears completely.

Besides the chemistry itself there is also 'thing knowledge' - getting to grips with how things like burettes, pipettes and pipette fillers are designed to work.