CBSE Class 8 Answered
Petroleum
Petroleum is a mixture of hydrocarbons. This contains hydrocarbons with various molecular weights. These hydrocarbons may be aliphatic, aromatic, branched or unbranched. Petroleum is commonly used to indicate fossil fuel in gas, liquid and solid state. Hydrocarbons with a lower molecular weight (ex: methane, ethane, propane and butane) occur as gases. Heavier hydrocarbons like pentane, hexane and so on, occur as liquids and solids. Paraffin is an example for a solid hydrocarbon in petroleum. The proportion of each compound in petroleum differs from place to place.
Crude Oil
Except the gas component in the petroleum, the rest of the mixture is known as crude oil. It is a liquid. Alkanes, cycloalkanes, aromatic hydrocarbons are mainly found in crude oil. There are other organic compounds containing nitrogen, oxygen, sulfur and other metals. The appearance of crude oil may differ due to the composition of it. Usually it is black or dark brown in color. Crude oil is refined, and its components are mainly used as fuels for automobile, machinery, etc.