Fractional distillation of crude oil

Heated crude oil vaporises and enters a fractionating column. Shorter carbon chains have lower boiling points, so they rise higher before condensing. Longer carbon chains condense lower down. The carbon chains are shown as small flexible molecules that bend along the chain rather than moving as one rigid piece.

Animation speed 1× Molecule density Highlight fraction
Crude oil fractions
What is happening?
Crude oil is heated. Many hydrocarbons vaporise and rise into the fractionating column.
Selected fraction
Showing all fractions.

The column is hottest at the bottom and coolest at the top. Smaller hydrocarbons rise higher because they have lower boiling points.

Fraction Carbon chain Approx. temp Uses

Teaching note: this is a conceptual model. Fraction ranges and temperatures vary between sources. The key idea is: shorter chain = lower boiling point = condenses higher up the column.