Saturated and unsaturated fats
A fat's constituent fatty acids may also differ in the C/H ratio. When all three fatty acids have the formula CnH(2n+1)CO2H, the resulting fat is called "saturated". Values of n usually range from 13 to 17. Each carbon atom in the chain is saturated with hydrogen, meaning they are bonded to as many hydrogens as possible. Unsaturated fats are derived from fatty acids with the formula CnH(2n-1)CO2H. These fatty acids contain double bonds within carbon chain. This results in an "unsaturated" fatty acid. More specifically, it would be a monounsaturated fatty acid. Polyunsaturated fatty acids would be fatty acids with more than one double bond; they have the formula, CnH(2n-3)CO2H and CnH(2n-5)CO2H. Unsaturated fats can be converted to saturated ones by the process of hydrogenation. This technology underpinned the development of margarine.
Saturated and unsaturated fats differ in their energy content and melting point. Since unsaturated fats contain fewer carbon-hydrogen bonds than saturated fats with the same number of carbon atoms, unsaturated fats will yield slightly less energy during metabolism than saturated fats with the same number of carbon atoms. Saturated fats can stack themselves in a closely packed arrangement, so they can freeze easily and are typically solid at room temperature. For example, animal fats tallow and lard are high in saturated fatty acid content and are solids. Olive and linseed oils on the other hand are highly unsaturated and are oily.