Question

Evaporation is used to separate-
A) Salt from water
B) Pepper and sand
C) Sand and water
D) Camphor and NaCl

Answer 1

Hint: Evaporation is a process in which a substance in liquid state is converted into vapour phase. It is a slow process at room temperature and finally it leaves back the solid phase in the solution.

Complete step by step solution:
Evaporation is the process which is useful to vaporize the liquid phase from a solution and to separate solute and solvent from a solution.
-Evaporation is a natural process and also done by giving an external amount of heat to accelerate the reaction.
- Evaporation is an endothermic reaction that takes up the heat or temperature from the surroundings.
From the definition we know it is only used for solutions and not for mixture of substances in the same phase.
-From the above options given pepper and sand is in the same phase i.e. the solid phase so it can’t be the answer. Another one is of camphor and NaCl, here also both are in solid phase but they both are having different physical properties as Camphor is a sublimable substance, the mixture is separated by sublimation process.
And the final options left are sand and water and salt from water. Sand particles are much heavier than salt and it is insoluble in water. So if we make the sand solution and keep it aside for few hours the sand settles down and can be easily separated through filtration or decantation process
So the answer is salt from water. The boiling point of salt is very much higher than that of water so water evaporates first when it reaches its boiling point and the salt will remain in the beaker in the solid state. This process takes much time in ordinary temperature but can accelerate the reaction by giving the temperature.

-So the correct option for this question is option (A).

Additional information:
Salt and water can also be separated using a distillation process in which water is collected in a separate beaker and the salt remains in the container.
Large amount of common salt is prepared through an evaporation process near the seashore where large plots are allocated and the sea water is allowed to stand for a long time, the water evaporates by the heat of the sun and the salt remains back, which undergoes many purification methods and is sold.
Note: Students may get confused by the definition of evaporation that the liquid phase is converted into vapour phase so every solution can be separated as such. But in this question itself the sand and water is removed through the filtration process since it's an easier and efficient one and here the sand settles down easily and can be removed.