In chemistry, hydrophobicity (from the Attic Greek hydro, meaning water, and phobos, meaning fear) is the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water.Hydrophobic molecules tend to be non-polar and, thus, prefer other neutral molecules and non-polar solvents. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar from polar compounds.