What is a chemical reaction?

In a chemical reaction, a chemical change takes place. The reactants lose their properties, and the products formed usually have properties different from the reactants. This happens in a combustion reaction too. For example, on igniting, grey iron or steel wool burns in air with a bright light and a blue-black brittle substance remains as the residue, which is heavier than steel wool. In the combustion reaction, iron reacts with oxygen in the air. The new substance formed in this oxidation reaction is iron oxide. The term ‘oxidation’ is derived from the Latin word oxygenium, meaning oxygen. The more easily the electrons move from the outermost shells, the more reactive the substance is. Noble gases such as argon and neon are not reactive. For this reason, we breathe in the same argon atoms today which dinosaurs breathed in.