Here's why:
* Petroleum is a mixture: It's not a single substance, but a complex mixture of many different hydrocarbons.
* Hydrocarbons have different boiling points: The size and structure of a hydrocarbon molecule affects its boiling point. Smaller, simpler molecules (like methane) have lower boiling points, while larger, more complex molecules (like asphalt) have higher boiling points.
* Fractional distillation: This process uses the difference in boiling points to separate the hydrocarbons. Petroleum is heated to a high temperature, causing the hydrocarbons with lower boiling points to vaporize first. These vapors rise through a fractionating tower, where they are collected at different levels based on their boiling point.
So, in short, the different boiling points of the hydrocarbons in petroleum allow them to be separated through fractional distillation.
