Aim: To separate a solvent from a solution based on differences in boiling points.
Principle: When a solution is heated, the solvent evaporates first (lower boiling point), the vapor travels through a condenser where it cools and condenses back into liquid (distillate).
Example: Obtaining pure water from salt water (NaCl solution). Salt remains in the flask. Water boils at 100°C, salt remains as residue.
• Steam and the boiling solution scald — keep hands clear of the flask and joints; the glassware stays hot after the flame is off.
• Add anti-bumping granules before heating to stop sudden violent boiling that could throw hot liquid out.
• Connect the condenser water correctly (in at the bottom, out at the top) and check joints are secure before heating.
• Do not seal the apparatus — trapped vapour builds up pressure. Do not heat the flask to dryness.
• Bunsen safety: tie back hair, wear goggles, use a heat-proof mat.
Lock a prediction before switching on the heat.