1. This is a word equation for a chemical reaction: Reactants Products Magnesium + hydrochloric acid Magnesium chloride + Hydrogen Word equations

2. No atoms are created or destroyed in a chemical reaction. There should be the same number of atoms of each type of element on each side of the equation. Ie. # atoms in reactants = # atoms in products Magnesium + Oxygen Magnesium oxide Symbol equations

3. (s) (l) (g) (aq) E.g. H 2 O 2 CO 2 H 2 O C State symbols

4. You can never change a formula when balancing an equation. You can only put number in front of a formula. Lets consider two molecules of CO 2 : C 2 OX CO 4 X C 2 O 2 X 2CO 2 Balancing equations

5. Word eq n : hydrogen + oxygen water Skeleton eq n : H 2 + O 2 H 2 O Atom count:2 x H2 x O 2 x H 1 x O Balanced2H 2 + O 2 2H 2 O Chemical Equation Making water

6. Symbol eq n : H 2 + O 2 H 2 O Balance O:H 2 + O 2 2H 2 O Atom count:2xH 2xO 4xH 2xO Balance H: 2H 2 + O 2 2H 2 O Atom count:4xH 2xO 4xH 2xO Making water

7. You try – balance these equations and add state symbols. C + O 2 CO 2 H 2 + O 2 H 2 O CH 4 +O 2 CO 2 + H 2 O

8. Reversible reactions The products of the reaction can react and make the reactants. Changes that can go backwards or forwards. Show with a double arrow: Can you think of any reversible reactions?