The boiling point increases as the number of carbon atoms (chain length) increases.
The viscosity increases as the number of carbon atoms (chain length) increases.
The greater the number of carbon atoms (chain length), the darker in colour that fraction is.
The viscosity of a fluid describes how easily it flows. Water has a low viscosity, it flows very easily. Crude oil has a higher viscosity than water, it does not flow very easily.
| Fractions (in order) | Properties |
|---|---|
| Refinery gases | Smallest molecules. Lowest boiling point. Lowest viscosity. Lightest in colour. |
| Gasoline | |
| Kerosene | |
| Diesel | |
| Fuel oil | |
| Bitumen | Largest molecules. Highest boiling point. Highest viscosity. Darkest in colour. |