Reason from qualitative tests

Use clean apparatus and a fresh small portion for each test. Add reagent gradually with mixing; observe a few drops, excess reagent and warming separately when instructed. Write the actual colour and physical change. A blue solution and a pale-blue precipitate are different observations. Name a gas only after the appropriate confirmatory test.

For a simple organic test, record the reagent and what changes. Bromine water changing from orange to colourless is consistent with an alkene under the relevant conditions, but decolourisation alone is not a universal proof of C=C because other substances can also react. Use the stated candidate structures and any other evidence to narrow the conclusion.

In G2 the gas tests you must know are hydrogen (lighted splint, squeaky pop), oxygen (glowing splint relights) and carbon dioxide (limewater turns milky). A question may describe another test and ask you to record or interpret what you would see: describe the change first, then state what it suggests.