A chemical reaction is when one or more substances change and produce one or more new chemical substances. The substances that are involved in a chemical reaction and that are changed by it are ...

Every chemical reaction involves a change in energy because different substances hold different amounts of energy. During the reaction, bonds inside the substances that are reacting together must ...

All living things depend on millions of chemical reactions that happen constantly ... they need to go on a special diet for life. Another, less severe, example is lactose intolerance. Many people can ...