Separation of Substances: 18 MCQs with answers

No, separation only changes arrangement, not the substance.

Separation is a physical process. It pulls components apart without changing what they are chemically, so the salt remains salt.

Difference in weight

Winnowing uses moving air to blow away lighter husk while heavier grain falls straight down, so it depends on a difference in weight.

Threshing

Threshing is beating the dried stalks to separate grain from the stalk. Winnowing comes after to remove husk.

Filtrate

The liquid that passes through the filter is called the filtrate. The solid left on the paper is the residue.

Handpicking

Handpicking works when unwanted pieces are large enough to see and few enough to pick out, like stones from rice.

True

**Evaporation** is used to obtain salt from sea water; the water turns to vapour and salt is left behind.

Evaporation

Filtration cannot catch dissolved salt. Evaporation turns the water to vapour and leaves the dissolved salt behind.

Distillation

Evaporation loses the water as vapour. Distillation collects the liquid as distillate after condensation and leaves the solid behind, recovering both.

Sedimentation

Sedimentation is when heavier solid particles sink to the bottom of a liquid. The clear liquid can then be decanted.

It speeds up sedimentation.

Alum helps the mud particles settle faster, speeding up sedimentation so the clear water can be decanted sooner.

Iron filings and sand

Magnetic separation works when one component is magnetic. Iron filings are magnetic, so a magnet pulls them out of sand.

Bran from flour by particle size

Sieving separates particles of different sizes. The sieve holes let fine flour through while bran stays behind.

It separates insoluble solids from liquids.

Filtration only works when the solid is insoluble. Dissolved particles are too small and pass through the filter paper.

Both A and R are true, and R correctly explains A.

Distillation recovers both components because the vapour is condensed back into liquid (distillate) while the dissolved solid stays in the flask. This is exactly why it is preferred when both are needed.

Magnetic separation, then filtration, then evaporation

First a magnet removes iron filings. Then filtration separates insoluble sand from the salt solution. Finally evaporation recovers the dissolved salt.

II and III only

Statement I is wrong — evaporation loses the liquid as vapour. Statements II and III are correct: distillation recovers both components, and condensation turns vapour back into liquid.

1. Magnetic separation, 2. Filtration, 3. Evaporation

The correct sequence is: first, use magnetic separation to remove iron filings, then filtration to separate sand from the saltwater solution, and finally evaporation to recover the salt from the remaining solution.

Use distillation to recover both salt and water.

Distillation is the correct method because it allows for the recovery of both the dissolved salt and the water. Filtration cannot be used since salt is dissolved, and evaporation would result in losing the water.