Experiment 10 — Choose the Right Technique

Topic: Chemistry · Classes 6–7 · Separation of substances

Aim: Pick the correct separation technique for all four mixtures.

Daily: Every one of these happens in Indian homes and farms: winnowing grain on a windy day, churning curd for butter, letting muddy water settle before use, and drying salt from sea water.

M1: Husk and grain: use winnowing — the wind carries the lighter husk further than the heavier grain.

M2: Butter from curd: use churning — spinning throws the lighter fat globules together so they collect on top.

M3: Muddy water: let it stand so the heavy mud settles ( sedimentation ), pour off the clear water ( decantation ) and then filter the rest.

M4: Camphor and salt: use sublimation — on warming, camphor turns straight from solid to vapour and can be collected again on a cool surface, leaving the salt behind.

Question: Which technique separates camphor from salt?

Exp: Camphor sublimes — it turns straight from solid to vapour on warming, then re-forms on a cool surface.

Question: Winnowing separates substances by difference in…

Exp: Wind carries the lighter component further.

Exp: Decantation is the pouring step that follows.

Question: Which pair CANNOT be separated by filtration?

Exp: Dissolved salt passes through the filter; you must evaporate.

Question: Sublimation means a solid changes…

Exp: No liquid stage is involved.