What is Polymerization?
'''Polymerization''' or '''polymerisation''' is the process in which small [[molecule]]s, called [[monomer]]s, join [[Chemistry|chemically]] to produce a very large [[chain]]-like or [[network]] molecules, called [[polymer]]<nowiki/>s. The monomer molecules may all be alike, or they may represent two, three, or more different [[Chemical compound|compound]]s. Usually at least 100 monomer molecules must be combined to make a product that has certain unique physical properties—such as [[elasticity]], high [[tensile strength]], or the ability to form [[fibre]]s—that differentiate polymers from substances composed of smaller and simpler molecules. Often, many thousands of monomer units are [[Wikt:incorporated|incorporated]] in a single molecule of a polymer. The formation of stable [[Covalent bond|covalent chemical bonds]] between the monomers sets polymerization apart from other processes, such as [[crystallization]], in which large numbers of molecules aggregate under the influence of weak intermolecular forces. [[Alkene]] molecules can react with themselves, by adding polymerization to form 'plastic' or polymeric materials. When a [[catalyst]] (a substance that speeds up chemical processes) is added to the reaction, or it is heated under pressure, unsaturated [[alkene]]s link together, when the double bond partially breaks. [[Polyethene]] is a cheap and useful plastic used for plastic bags and bottles, it is also very flexible and quite strong. {{chem-stub}} [[Category:Polymer chemistry]]