The Law of Conservation of Mass: The total mass of the reactants must equal the total mass of the products Total mass of reactants = Total mass of products

This makes sense because atoms cannot be created or destroyed Atoms present at the beginning of the reaction must still be present after the reaction has taken place How?? Atoms rearrange themselves, bonding to new atoms to make a different product Fruit salad game example, Square dancing

So when you write a chemical equation… The number of atoms of each type must be the same on each side Equations must be balanced! This can be done in 4 easy steps reactants products

Step 1: Write the word equation products Methane + oxygen  carbon dioxide + water reactants

Step 2: Write the skeleton equation Replace each name with its formula Methane + oxygen  carbon dioxide + water CH4 + O2  CO2 + H2O

Step 3: Count atoms Count the number of atoms of each type in reactants (left side) and products (right side) CH4 + O2  CO2 + H2O Type of Atom Reactants Products Balanced? C 1  H 4 2  O (2+1) = 3

Step 4: Balancing Multiply each compound by the appropriate coefficients to balance the number of atoms Start with the atom that is in the least number of compounds (less disruption) Usually leave oxygen and hydrogen for last (very common atoms) Trial and error (be patient )

Step 4: Balancing CH4 + O2  CO2 + 2H2O Type of Atom Reactants Products Balanced? C 1  H 4 O 2 (2+2) = 4  Remember when you put a coefficient in front of a compound, ALL atoms are multiplied!!

Step 4: Balance CH4 + 2O2  CO2 + 2H2O Type of Atom Reactants Products Balanced? C 1  H 4 O

Human Balancing Act Sodium + Chlorine Gas  Table Salt Na (s) + Cl2 (g)  NaCl (s) 2 Na (s) + Cl2 (g)  2 NaCl (s)