Key facts & rules

• Filtration: separates insoluble solid from liquid.
• Evaporation/crystallisation: separates soluble solid from solution.
• Simple distillation: separates a liquid from a solution (e.g. water from salt solution).
• Fractional distillation: separates liquids with different boiling points.
• Paper chromatography: separates dissolved substances by how far they travel on paper with solvent.
• Test for H₂: lit splint → squeaky pop.
• Test for O₂: glowing splint → relights.
• Test for CO₂: limewater → turns milky.
• Test for Cl₂: damp litmus paper → bleaches white.
• Flame tests: Li→red, Na→yellow, K→lilac, Ca→orange-red, Cu→blue-green.
• Test for sulfate SO₄²⁻: add Ba²⁺(aq) → white precipitate BaSO₄.
• Test for halide ions: add AgNO₃(aq): Cl⁻→white ppt; Br⁻→cream ppt; I⁻→yellow ppt.