What is Fractional Distillation and how does it work?

Fractional Distillation is a method used in industry to separate different sized hydrocarbons (long chains that consist of hydrogen and carbon). This is useful as it means crude oil can be separated into more useful, purer products - such as petroleum (for cars), methane, propane and butane (for gas ovens and heaters in homes).
It works on the basic principle of evaporation and condensation. When the crude oil is fed into the fractional distillation tower, it is heated to above 300 degrees Celsius. When this happens, most of the molecules in the oil evaporate (meaning they turn to gas). The biggest molecules do not turn to gas because they are too heavy, so have a higher boiling point, and flow out the bottom as a liquid. As you go up the tower, the temperature inside decreases - this means that the heavier molecules at each stage will condense into a liquid, and will be collected off. Only the lightest, smallest molecules will be collected off the top of the tower as a gas.