Fractional distillation is used to separate mixtures based on differences in

• A. Boiling points
• B. Densities
• C. Viscosities
• D. Colors

Answer: (A)

Fractional distillation relies on differences in how easily components vaporize, i.e., their boiling points. When a mixture is heated, the component with the lower boiling point tends to form vapor first. The fractionating column provides many surface contacts where vapor can condense and re-vaporize, refining the separation so components with closer boiling points can be kept apart. This lets each component be collected as a distinct fraction as the temperature is increased.

Densities, viscosities, and colors aren’t what drive this process. Densities affect how liquids settle or separate, viscosities relate to flow, and color is a visual property; none of these determine which part of the mixture becomes vapor first.