Which statement correctly describes how fractional distillation works?

• A. The crude oil is cooled and vapors collected.
• B. The crude oil is heated and the vapours rise up the column, condensing at different levels, and liquids run out via pipes.
• C. The crude oil is filtered through a membrane.
• D. The crude oil is burned to produce heat.

Answer: (B)

Fractional distillation separates a liquid mixture into fractions with different boiling points using a column with many temperature zones. When the crude oil is heated, its components form vapors that rise up the column. As they ascend, they encounter cooler regions and begin to condense at the level where their boiling points are reached, so liquids are drawn off through outlets at different heights. Lighter, low-boiling components stay in the vapor longer and condense higher up, while heavier components condense lower down. This description matches the process: heating to form vapors, rising through the column, condensation at various levels, and collection of liquids via pipes. The other statements don’t fit distillation: cooling to collect vapors isn’t how distillation works, filtration through a membrane is a different separation method, and burning to produce heat is combustion, not distillation.