1. Law of Conservation of Mass

2. Think about the following question: –If you burned a log in the fireplace, would the mass of the products (smoke, ashes, etc.) be the same as the reactants (the wood)?

3. Law of Conservation of Mass Yes! In a chemical reaction, the total mass of the reactants is always equal to the total mass of the products

4. Law of Conservation of Mass Example: Burning of Methane Methane + Oxygen → Water + Carbon dioxide CH 4 + O 2 → H 2 O + CO 2

5. Law of Conservation of Mass CH 4 + O 2 → H 2 O + CO 2 4 Hydrogen atoms on the left hand side (reactants); only 2 on the right side (products) Where did they go? Atoms cannot be created or destroyed, just rearranged in a chemical reaction NEED TO BALANCE THE EQUATION!

6. Law of Conservation of Mass CH 4 + 2 O 2 → 2 H 2 O + CO 2 The 2 means that there are 2 oxygen and water molecules Now there are equal numbers of atoms on both sides of the reaction