Which of the following pairs of substances can best be separated through distillation?
A. Salt and sand
B. Sand and soil
C. Water and solid
D. Water and alcohol
The correct answer and explanation is:
The correct answer is D. Water and alcohol.
Distillation is a separation technique that relies on differences in boiling points of substances in a mixture. When a mixture is heated, the component with the lower boiling point vaporizes first. The vapor is then cooled and condensed back into liquid form, effectively separating it from the other components.
Here is why option D is the best choice:
- Water and alcohol (such as ethanol) have different boiling points. Ethanol boils at about 78.4°C, while water boils at 100°C at standard atmospheric pressure. When a mixture of water and alcohol is heated, the alcohol vaporizes first. The vapor can be collected and condensed separately, allowing the two liquids to be separated effectively by distillation.
Why the other options are less suitable:
- A. Salt and sand: Both salt and sand are solids, and distillation separates substances based on boiling points. Since neither salt nor sand vaporizes under normal distillation conditions, distillation is not suitable for separating these two solids.
- B. Sand and soil: Soil is a mixture of various solid particles including sand, clay, and organic matter. Since both components are solids and do not vaporize, distillation cannot separate them.
- C. Water and solid: Solids dissolved or suspended in water typically do not vaporize during distillation. Distillation can remove dissolved solids from water if the solid remains behind when water vaporizes, but if the solid is suspended or mixed physically, other methods like filtration or sedimentation are more appropriate.
In summary, distillation is most effective for separating mixtures of liquids with different boiling points. The mixture of water and alcohol fits this criterion well, making distillation the ideal choice for their separation.