1. Chemical Ideas 1.2 Balancing equations

2. Balanced chemical equations Tell us the reactants and products in a reaction, and the relevant amounts involved. Equation is balanced so that there are equal numbers of each type of atom on both sides. CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 0 (l)

3. Steps for balancing equations The reaction between Ca and H 2 0 STEP 1 Decide what the reactants and products are Calcium + water  calcium hydroxide + hydrogen STEP 2 Write formula for the substances and state symbols Ca (s) + H 2 0 (l)  Ca (OH) 2 (aq) + H 2 (g) STEP 3 Balance the equation so same number of the different atoms on both sides Ca (s) + 2H 2 0 (l)  Ca (OH) 2 (aq) + H 2 (g) Equations can only be balance by putting numbers in front of the formulae, you cannot balance them by altering the formulae themselves because you would create different substances

4. State symbols State symbols are included in chemical equations to show the physical state of the reactants and products (g) Gas (l)Liquid (s)Solid (aq) aqueous solution The law of conservation of mass French chemist Antoine Lavoisier In 1774 found that if nothing is allowed to enter or leave a reaction vessel, the total mass is the same after as it was before Atoms are not created or destroyed in chemical equations they are simply rearranged…… so equations must balance!