A chemical reaction is a process where reactants are converted into different products, represented by chemical equations. Chemical equations must be balanced to show mass is conserved, with the same number of atoms before and after the reaction, using coefficients as needed. There are several types of chemical reactions including synthesis, decomposition, single replacement, and double replacement.

1. Chemical Reaction Definition: a process in which one or more substances are converted into new substances with different physical and chemical properties.

2. Chemical Reactions Involve two types of substances: those before the reaction (reactants) and those after the reaction (products). Reactants Products

3. Chemical Reactions Represented by sentences known as chemical equations. Example: Calcium + oxygen calcium oxide + is read as “reacts with” is read as “yields” or “produces” Calcium reacts with oxygen to yield calcium oxide.

4. Chemical Reactions To show that mass is conserved in a reaction, the number of atoms of each element must be the same before and after a chemical reaction Called a balanced equation To balance a chemical equation, use coefficients, whole numbers written before the formulas of reactants and products. Example: 2 H 2 + O 2 2 H 2 O

5. Types of Chemical Reactions Direct combination (synthesis) Example: 2Na + Cl 2 2NaCl Decomposition Example: CaCO 3 CaO + CO 2 Single-Replacement Example: Mg + CuSO 4 MgSO 4 + Cu Double-Replacement Example: CaCO 3 + 2HCl CaCl 2 + H 2 CO 3