Chemical Reactions

A reaction turns starting materials (reactants) into new substances (products). The arrow means 'becomes'. Nothing is lost — the same atoms are just rearranged.

How liquid resin becomes a hard solid. Heat or a hardener makes the polymer chains stitch together into one giant network. Once cured, it can't melt back — like a boiled egg.

Many monomers joining into a long polymer chain. Some reactions add units one by one; others link pieces and release a small molecule (like water) each time.

Exothermic reactions give off heat (curing epoxy gets warm on its own); endothermic ones need heat put in. Managing this heat is a big part of making large composite parts.

A substance that speeds up a reaction without being used up. A tiny amount of hardener can trigger a whole batch of resin to set.

Reacting with oxygen. Rusting iron and burning wood are both oxidation — one slow, one fast. It's why some materials degrade in air or at high temperature.

There are two routes to a long chain. In chain-growth, monomers add one at a time onto a growing active end, like a train gaining carriages — that is how polyethylene is made. In step-growth, small pieces join up in any order, often releasing a tiny by-product, like nylon. The route shapes how the plastic turns out.

A reaction where water breaks a chemical bond apart — the reverse of the reaction that formed it. It is how some plastics slowly weaken in damp conditions, and it is used on purpose in medicine: a dissolving stitch is designed to be hydrolysed harmlessly away by the body once its job is done.