Physical Methods to Separate Mixtures (Class 11 Chemistry)

In a mixture the parts are just mixed together. They keep their own properties and are NOT joined by chemical bonds. So a physical method (like heating, filtering, or a magnet) can pull them apart. In a compound the elements are joined by chemical bonds in a fixed ratio, so only a chemical reaction can break them. This exact difference is a common NEET one-liner.

Look at the difference in properties between the parts. If one is solid and one is liquid, use filtration. If a solid dissolves in the liquid, use evaporation or distillation. If two liquids mix fully (miscible) and have different boiling points, use distillation. If two liquids do not mix (immiscible, like oil and water), use a separating funnel. If one solid turns straight to gas on heating, use sublimation. Always match the method to the property that is DIFFERENT.

Salt water is a homogeneous mixture, so filtration will NOT work (salt is dissolved, not floating). Use evaporation to get the salt back, or use distillation if you want pure water back too. In distillation the water boils, turns to vapour, then cools back to liquid in the condenser, leaving salt behind.

Filtration separates an insoluble solid from a liquid (like sand from water) using filter paper. Distillation separates a dissolved solid from a liquid, or two miscible liquids with different boiling points, by boiling and then cooling the vapour. Filtration uses particle size; distillation uses boiling point.

Use distillation (or fractional distillation if boiling points are close). The liquid with the lower boiling point turns to vapour first. That vapour is cooled in a condenser and collected. This works because the two liquids have different boiling points, even though they mix fully.

Use sublimation when one solid in the mixture turns directly into gas on heating (no liquid stage) and the other does not. Examples: camphor, ammonium chloride, iodine, naphthalene. On heating, the sublimable solid becomes vapour, then cools and re-forms as solid on a cool surface, separated from the leftover solid.

Both remove a solid from a solution, but crystallisation gives PURER solid because impurities stay in the leftover liquid (mother liquor). Evaporation just dries everything, so impurities stay mixed in the solid. NEET may ask which gives the more pure product: crystallisation.

Chromatography separates components of a mixture that have different rates of movement over a surface (like different coloured dyes in ink). Parts that stick less to the paper move faster and travel further. It is used when the amounts are very small or the parts are very similar.

It is a physical change. No new substance is formed, and the parts keep their original properties. That is why physical methods are enough for mixtures.

Yes. Magnetic separation works when one part is magnetic (like iron filings) and the rest is not (like sulphur powder or sand). The magnet pulls out the iron.

Crystallisation. It gives a purer solid than simple evaporation because impurities stay behind in the mother liquor (the leftover solution).

A separating funnel. The denser liquid settles at the bottom and is drained out first, leaving the lighter liquid on top.

NEET asks conceptual one-liners on which method suits which mixture and on the mixture vs compound difference. Knowing the property each method uses (boiling point, solubility, particle size, magnetism) lets you answer quickly without memorising.