Question

How can we separate sugar from a mixture of sugar and water like we can remove acetone from water?

Answer 1

A mixture of sugar and water is nothing but its solution and is completely homogenous in nature which means that these two cannot be separated by simple physical methods of separation like hand picking , filtrations or centrifugation as the sugars particles are uniformly distributed in water.

Complete answer:
A mixture of sugar and water is a perfect solution in which sugar acts as a solute (the substance being dissolved) and water (usually present in excess) acts as the solvent (the substance that dissolves the solute).
Solutions can be of various kinds like solid-liquid, liquid-liquid, gas-liquid and many more. The sugar-water solution is a solid-liquid solution.
Once a homogenous solution is formed, the solute particles occupy the empty spaces between the liquid particles making them invisible to the naked eye. Hence methods like filtration cannot be used.
Sugar-water can be separated from each other by bringing a change of state in one of the two components. Since it is not practically possible to remove sugar (solid) as a gas, we can transform the water present in the mixture into water vapour. On doing so, the water vapour will escape into the atmosphere and the container will be left with sugar alone.
A similar method is applicable to the acetone-water mixture which is a liquid-liquid solution but acetone is more volatile (having higher vapour pressure) than liquid and evaporates at room temperature. The significant difference in the boiling points between acetone and water makes it easy to separate the two by heating the mixture up to the boiling point of acetone, which then escapes as vapour leaving it as pure water. This method of liquid-liquid separation based on boiling points can also be achieved by a technique called distillation.
Hence, sugar-water can be separated by evaporating all the water present in the mixture.

Note:
The process of evaporation involves the transformation of only those liquid molecules escaping as vapour that are present on the surface of the liquid. Evaporation happens layer by layer and is only limited to the surface particles and does not require temperatures as high as the boiling point of the liquid.