Crude Oil

Question 1

What is Crude Oil?

Answer 1

Crude oil is a mixture of substances most of which are hydrocarbons (a compound containing only hydrogen and carbon). Crude oil is limited in quantity and is an non-renewable source. There are a lot different hydrocarbons of various sizes in crude oil. This ranges from molecules with just a few carbon and hydrogen atoms to molecules containing over 100 atoms. As the number of carbon atoms increases, the physical properties of the compounds change.

As the molecules get bigger, a number of changes occur:

1. As the molecules of hydrocarbons get bigger, intermolecular forces of attraction between the molecules become stronger.
2. The larger the molecule, the higher the boiling point. This is because large molecules are attracted to each other more strongly than smaller molecules of hydrocarbons. More energy is needed to break these stronger intermolecular forces of attraction to produce the widely separated molecules in the gas. The boiling point has to be high in order for it to change into a gas and the liquid boils.
3. The bigger the hydrocarbon, the more slowly it evaporates at room temperature. This is because the bigger molecules are more attracted to each other and so don’t turn into a gas easily.
4. Liquids containing small hydrocarbon molecules are more runny. If the molecules are bigger, they will flow less easily because of the stronger forces of attraction between them which makes them closer to each other (because they are attracted to each other) and so can’t flow (because solids can’t flow easily).
5. The larger the molecule, the darker the liquids become in colour.
6. Bigger molecules of hydrocarbons do not burn as easily as smaller ones. This limits the use of the bigger ones as fuels.

Question 2

Separating crude oil

Answer 2

When crude oil is transported to the refinery (a place where you remove unwanted elements) it is a thick black smelly liquid. Crude oil itself has no uses. We learned that crude oil