If we have just one carbon atom (and hence four hydrogens), we have the gas perhaps because it not only emanates from the ground, but also the rear end of cows. The next three in the series are ethane, propane and butane, which have, respectively, two, three and four carbons in their chains. These are also gases at ambient temperatures and pressures, the latter two being commonly used for heating and cooking. Liquids, commonly used as auto and jet fuels typically have carbon chain lengths of 6–12. As we increase the carbon chain lengths further, the viscosity increases and we go from liquid materials used for baby oils, to “semi-solid” materials used as soft and hard candle waxes. At even higher carbon chain lengths, typically exceeding 30,000, we encounter hard, solid polyethylenes.
Finally, it is important to recognize that all polymers, be they natural or synthetic, are simply giant long chain molecules or macro-molecules. It's all chemistry, and there really is no basic difference between a natural or synthetic polymer, in that both obey the same physical laws. Cellulose, for example, the natural polymer that is found in cotton and numerous other plants (and the most abundant polymer on the face of the planet), is a long chain macromolecule composed of carbon, hydrogen and oxygen. So is the synthetic polyester fiber, poly(ethylene terephthalate) (PET). It's just that the arrangement (architecture) of the atoms in the two polymer chains is different. However, it is common practice to distinguish between natural and synthetic polymers and also classify them in terms of plastics, fibers, elastomers, composites, paints, adhesives, etc. Various types of materials and some of their natural and synthetic counterparts are shown in the table below. We will compare and contrast the structure of some natural and synthetic polymers in later chapters.