Hydrocarbons in water

Hydrocarbons are nonpolar, which means that they generally don't mix well with water. Simple hydrocarbons that are liquid at room temperature, such as hexane, have a lower density than water, and therefore forms a separate layer on top of water. These layers are called phases. This two-phase system can be used for e.g. extracting organic compounds from a water sample into hexane, which can have many advantages in analytical chemistry.