1. Chemical Equations & Balancing

2. What is a chemical equation? A standard way to describe a chemical reaction. –This means that scientists worldwide use this system. Show the number and combinations of elements & compounds involved in the reaction.

3. Chemical Equations … 2 Parts to a chemical equation: –Reactants = original substance(s) (substances before any reaction occurs) –Products = created during the reaction (ending substances) http://www.agoosa.com/images/baking-soda.jpg http://scoutmaster.typepad.com/photos/uncateg orized/2007/03/18/vinegar.jpg NaHCO 3 CH 3 COOH http://www.achilles- online.com/catalog/pics/Sodium_ Acetate__Anhydrous.jpg NaCH 3 COO http://keetsa.com/blog/wp- content/uploads/2008/03/ water-conservation.jpg H2OH2O http://www.scienceclarified.com /images/uesc_02_img0110.jpg CO 2

4. General Chemical Equations: Reactant + Reactant  Product + Product Not all reactions have 2 reactants and 2 products (could be one or more for each). Reactants written before the arrow. Products written after the arrow. Arrow represents chemical reaction.

5. For example: Label the reactants and products in this equation. How do you say this? Sodium and chlorine react to form sodium chloride. 2Na + Cl 2  2NaCl ReactantsProduct In chemical reactions, the number and kinds of elements are always the same!

6. Chemical Equations also show Conservation of Mass: There must be the same amount of each element in the reactants as in the products (although the element could be part of different compounds). http://media.photobucket.com/image/balance%20scales/nb est221/scales.jpg

7. Coefficients: Used to show conservation of mass in a chemical equation. Whole number put in front of a reactant or product to show a balanced chemical equation. 2Na + Cl 2  2NaCl Multiplies the element(s) found in that specific reactant or product.

8. Balancing Chemical Equations: Write each reactant and product. (Remember how ions form chemical bonds.) Add coefficients to change the number of atoms within a substance. Never change the subscripts!

9. 2 H 2 O 2  2 H 2 O + O 2 a.Reactants? b.H in reactants? c.H in products? d.O in reactants? e.O in products? f.Mass conserved? Why? g.Without coefficients – conservation? H O 4 = H = 2 X 2 = 4 = 4 O = 2 X 2 = 4 O = 2 + 2 = 4 YES! When Reactants = Products then mass is conserved! H 2 O 2  H 2 O + O 2 = 2 = 3 2 = Does NOT show Conservation of Mass because Reactants do NOT equal Products.