Methods of Separation: quick revision, 18 bites

Pick the Method That Matches the Property

Separate by what makes them different.

Every separation method exploits a **difference in properties** between the components of a mixture.

Takeaway. No single method works for all mixtures — the property difference decides the method.

Threshing: Grain Out of the Stalk

Beat the crop, free the grain.

Takeaway. Threshing separates grain from stalk — by hand, bullock, or combine harvester.

Winnowing: Let the Wind Do the Sorting

Wind carries chaff, grain falls straight.

Winnowing separates **chaff from grain** using wind or blowing air.

Takeaway. Winnowing works because chaff is lighter than grain — wind separates them into two heaps.

Chaff Has a Second Life

Waste chaff becomes cattle food.

The chaff separated during winnowing is **not wasted** — it is used as **fodder for cattle**.

Takeaway. Separation by-products can be useful — chaff becomes fodder.

Hand-Picking: When Impurities Stand Out

Spot it, pick it, done.

Hand-picking removes impurities (stones, dirt, husks, broken grains) that **look very different** from the food item.

Takeaway. Hand-picking is best for small quantities with visibly different impurities.

Filtration: Trapping the Insoluble Solid

Solid stays back, liquid slips through.

Filtration separates an **insoluble solid** from a liquid using a filtering device like filter paper.

Takeaway. Filtration works only if the solid particles are bigger than the pores of the filter.

Salt Water Won't Filter Out Salt

Dissolved salt slips right through.

Takeaway. Filtration handles insoluble solids only; dissolved solids need evaporation.

Evaporation: Liquid Leaves, Solid Stays

Heat it — water leaves, salt remains.

The mixture is heated; the liquid evaporates, leaving the solid behind.

Takeaway. Evaporation recovers a dissolved solid by removing the liquid as vapour.

Condensation: Gas Back to Liquid

Cold surface turns steam into drops.

Takeaway. Condensation needs a cold surface — it's how we recover evaporated water.

Recover Both Water and Salt

Boil, catch the steam, keep both.

Combining **evaporation + condensation** lets you recover both components of saltwater.

Takeaway. Salt stays in the kettle; water is collected in the container.

Salt + Sand: Two Steps, Not One

Dissolve, filter, then evaporate.

A salt–sand mixture needs **two processes** because the components differ in solubility.

Takeaway. Filtration + evaporation together separate salt from sand.

Solute, Solvent, Solution

Three words, one glass of sugar water.

Example: sugar (solute) + water (solvent) = sugar solution.

Takeaway. Solute dissolves in solvent to form a solution.

Soluble vs Insoluble

Salt vanishes; sand stays put.

Takeaway. Solubility decides whether you filter or evaporate.

Saturated Solution: No More Room

Extra sugar just sits at the bottom.

If you keep adding sugar and stirring, grains start collecting at the bottom — the solution has become saturated.

Takeaway. A saturated solution cannot dissolve any more solute at that temperature.

Heat Boosts Solubility

Hot water holds more sugar.

Heating a saturated solution lets you dissolve **more solute** — the quantity that dissolves in hot water is much more than in cold water.

Takeaway. Heating increases solubility, so a saturated solution can take more solute when warmed.

Stirring & Powder: Faster Dissolving

Stir it or crush it — it dissolves quicker.

Takeaway. Stirring and using powdered solute speed up dissolving — they don't change how much dissolves.

Don't Mix Up Solute and Solvent

The dissolver isn't the dissolved.

Takeaway. Solute dissolves; solvent dissolves it — keep the roles straight.

Match the Mixture to the Method

One line per mixture — exam gold.

Takeaway. Exam questions often ask 'which method?' — match the property difference to the method.