A hydrocarbon is simply a substance that contains carbon and hydrogen only. Alkanes and alkenes are two different families of hydrocarbon. When we are thinking about hydrocarbons the most important thing you need to know is that carbon forms four bonds. How many bonds does carbon form? Four.       

When we draw out these hydrocarbons we use the symbols for the elements – H for hydrogen and C for carbon – and then a line between to show a bond. The simplest of the alkanes is called methane (CH₄). Methane can be draw out as thus:

 Methane is the first member of the alkanes. Methane contains one carbon atom per molecule. We can tell how many carbon atoms a hydrocarbon has by looking at the prefix – the meth- in methane means one. Below is a list of the first eight prefixes:

A clever way to remember this is with the mnemonic: monsters eat people but people hate having October. 

                                                                                                                            The alkanes are described as a homologous series. A homologous series is a group of compounds that have similar chemical properties and can be represented by a general formula. The general formula for the alkanes is C_nH_{2n +2}. Where n stands for the number of carbons. Methane as we know has one carbon and four hydrogens. If we put one in the place of n we get C₁H_{2x1 +2} which would give CH₄ (we don’t write ones in chemical formulae). We can use this general formula to work out how many hydrogens are in a substance. For example how many hydrogens in octane? You could draw it out and count it or use the general formula. Using the general formula we work it out to be 18 (C₈H_2x8+2).