The reactions of functional groups listed in the specification.

The idea

Each functional group on this course has its own test-tube reaction, and each needs the right reagent, the right condition and a stated observation. An alkene decolourises orange bromine water at room temperature. A primary or secondary alcohol, warmed with acidified potassium dichromate(VI), turns it from orange to green. A carboxylic acid added to sodium carbonate or hydrogencarbonate solution fizzes, and the gas turns limewater milky. An aldehyde gives a silver mirror with Tollens' reagent or a red precipitate with Fehling's solution, both warmed in a water bath. A halogenoalkane, warmed with sodium hydroxide, acidified with nitric acid and treated with silver nitrate, gives a white, cream or yellow precipitate.

What earns the marks

• Naming the reagent as something that could be taken from a bottle, such as acidified potassium dichromate(VI).
• The condition, including warming in a water bath where the test requires it.
• The observation on a positive result, giving both the starting and the final appearance.
• Stating what is seen with a compound that does not react.

Common mistakes and how to put them right

• Testing the gas from a carbonate with a lighted splint instead of bubbling it through limewater.

• Cooling Fehling's solution instead of warming it, which AQA has flagged as a method error.

• Writing that bromine water "turns clear" rather than colourless.

• Giving the product formed instead of what would actually be observed.

Exam tips

• Write reagent, condition and observation as three separate items; a missing condition often costs a mark.
• Say "no change" explicitly for the compound that does not react.
• Name reagents in full, including the word acidified or ammoniacal where it applies.