In crude oil separation, as the length of the hydrocarbon chain increases the boiling point of the hydrocarbon goes up.
Methane, which is the molecule with the shortest hydrocarbon chain has only one carbon atom and is found as a gas. As the number of carbon atoms goes up so does the boiling temperature.
In crude oil, the very short hydrocarbons are gas, followed by liquids which get thicker with the length and finally appear almost like a solid.
This property is used in refining crude oil to separate the components like gasoline, diesel, jet fuel, kerosene, paraffin wax, tar, etc. The crude is slowly heated and depending on the boiling point of each compound it separates at a different temperature and is collected.