Question

Name the process
(i) to recover dye from black ink
(ii) to get cream from milk
(iii) to separate a mixture of water and acetone
(iv) to separate a mixture of salt and iodine

Answer 1

The process involved in the following:

(i) To recover dye from black ink:

1. The dye can be obtained from black ink by the process of evaporation.
2. The process of separating any substance from its solution by removing water is called evaporation.
3. Ink is a mixture of dye in water.
4. If we heat the ink indirectly on a watch glass (place it over a beaker half full of water and the beaker is placed over a burner) then the dye remains on the watch glass whereas water evaporates.

(ii) To get cream from milk:

1. Cream from milk can be obtained by the process of centrifugation.
2. This method involves separating solid particles suspended in the liquid.
3. The machine is rotated at high speed, this causes the denser particles to settle down at the bottom and the lighter particles to stay at the top when spun rapidly.
4. The solid fat particles were uniformly mixed all through the milk. After centrifuging, the lighter cream has collected at the top and milk without cream remained below.

(iii) To separate a mixture of water and acetone:

1. A mixture of water and acetone can be separated by the process of distillation.
2. Water (boiling point $100°\mathrm{C}$ )and acetone (b.p $56°\mathrm{C}$) are two miscible liquids and a mixture of miscible liquids can be separated by the process of distillation if the difference in boiling point is more than $25°\mathrm{C}$.
3. As the acetone has a lower boiling point than the water it will evaporate first and its vapours passed through a condenser, get cooled, and collected in the receiver, after some time no more vapours of acetone are formed (kept the temperature at $56°\mathrm{C}$).
4. The water is left behind in the flask.

(iv) To separate a mixture of salt and iodine:

1. The process in which a solid directly changes into the gaseous state without changing into liquid form is called sublimation.
2. Sublimation is used to separate the mixture of iodine and salt because iodine sublimes readily.
3. If we heat up the mixture of iodine and salt, iodine sublimes and the fumes cool down on the inner sides of the vessel.