6.1 Evidence for a Chemical Reaction. It is usually possible to tell when a chemical reaction has taken place, because every time that a chemical reaction occurs, there is both a chemical change and a physical change.
Most physical changes are visible.
In order to report or summarize information about a chemical reaction, chemists use chemical equations. The compounds on the left side of the arrow are referred to as reactants , while those on the right side are the products . The physical state of each of the components is indicated. The equation is balanced in terms of mass and charge. The net charge on both sides is zero.