1) The substances present before the reaction has occurred.
2) The substances formed after the reaction has occurred.
3) A negatively charged ion, typically non-metal, that gains electrons to become stable.
4) A positively charged ion, typically metal, that losses electrons to become stable.
5) A chemical reaction in which the reactants absorb heat energy from the surroundings to form products.
6) A chemical reaction in which the reactants release heat energy into the surroundings to form products.