A ___________________________ is a well defined example of a chemical change. A chemical ___________________________ can be used to show the changes that occur in a chemical reaction. In a chemical reaction, the substance on the left side of the arrow are the starting substance. These substances are called ___________________________. The substances on the right side of the arrow are the substances that result from the reaction. These substances are called ___________________________. The arrow is read as either produces or ___________________________. According to the law of conservation of ___________________________, atoms are neither lost nor gained during a chemical reaction. This law is illustrated when a chemical equation is ___________________. When this is done, there will be the same number of ___________________________ of each kind on both sides of the equation. In a chemical equation, the numbers that are placed in front of the symbols and the formulas are called ___________________________. They are necessary to keep the ___________________________ of atoms in balance. There are several rules for balancing an equation. First, write the correct _________________________ for each reactant and product. Next, choose the coefficients that make the number of atoms of each ___________________________ on each side of the equation equal. The correctly written formula should not be changed. If you change the formula of a substance, the equation is no longer ________________________. Changing a formula will indicate a ___________________________ different than the one intended. To balance the equation Mg + O2 à MgO, first choose coefficients to make the number of atoms of each element on each side of the equation equal. You would need to place a coefficient of ____________________