Chemical Reactions and Equations

## Making and Breaking Bonds A **chemical reaction** is when substances (called reactants) change into new substances (called products). During this process, chemical bonds are broken and new ones are formed. ### Writing Chemical Equations Chemists use equations to show what happens in a reaction. For example, when hydrogen and oxygen make water: \[ 2H_2 + O_2 \rightarrow 2H_2O \] The arrow shows the direction of the reaction, from reactants to products. ### Types of Chemical Reactions - **Combination:** Two or more substances join to form one (e.g., iron and oxygen make rust). - **Decomposition:** One substance breaks apart (e.g., water splitting into hydrogen and oxygen). - **Replacement:** Elements switch places (e.g., zinc and hydrochloric acid make zinc chloride and hydrogen). Chemical reactions are everywhere—from baking bread to powering cars!