Molecules are often separated by their size, shape or other properties. twomeows/Moment via Getty ImagesSeparating molecules is critical to producing many essential products. For example, in petroleum refining, the hydrocarbons – chemical compounds composed of hydrogens and carbons – in crude oil are separated into gasoline, diesel and lubricants by sorting them based on their molecular size, shape and weight. In the pharmaceutical industry, the active ingredients in medications are purified by