What Happens in Chemical Reactions?
Reactants Every chemical reaction starts with one or more reactants. Atoms, molecules or free electrons can participate. They combine, swap atoms or decompose into the reaction’s products. If a reactant is a single atom, it’s usually in ionized form—having too many or too few electrons. Molecules may be neutral or ionized. The reactants must be in physical contact in order to react. This usually means they occupy the same container and are being heated or mixed together. Some substances are stable, so they don’t react, or only at extremely low rates. A reaction happens only when the reactants and conditions favor it. Temperature To have a chemical reaction, the reactants must be at a finite temperature. At absolute zero, molecules lack the energy to react. Generally, the higher the temperature, the faster reactions proceed. Energy I Some reactions happen spontaneously, without additional energy. The reactants attract one another and combine, or an unstable reactant breaks into parts.
