Cooking oil and water do not mix; they form two separate layers. The apparatus shown is used to separate a mixture of cooking oil and water. The oil forms t...

This question tests separating immiscible liquids with a separating funnel, and choosing separation methods from solubility data.

(a) The apparatus is a separating funnel [1].

(b) To obtain separate samples:

1. place the mixture in the funnel with the stopper in, and let the two layers settle so the oil (U) sits above the water (L) [1];
2. open the tap and run the lower water layer L out into a beaker [1];
3. close the tap the moment the oil-water boundary reaches it, then run the upper oil layer U into a separate container [1].

(c) The two liquids can be separated because they are immiscible (they do not mix and form separate layers) [1], and they have different densities, so the less dense oil floats on top of the more dense water [1].

(d) Using the solubility table, iodine dissolves in ethanol but copper(II) sulfate does not:

1. add ethanol to the mixture so the iodine dissolves but the copper(II) sulfate stays solid [1];
2. filter the mixture [1];
3. the iodine solution passes through as the filtrate, giving a solution of only iodine (filtration) [1].

(e) To get pure dry salt and pure dry sand:

1. add water and stir so the salt dissolves but the sand does not [1];
2. filter to leave sand as the residue, then wash and dry the sand [1];
3. evaporate the salt solution (filtrate) to remove most of the water [1];
4. leave it to crystallise, then filter off and dry the salt crystals [1].

(f) A solvent is a liquid that dissolves a solute to form a solution [1].