1. Conservation of Mass & Word Equations

2. Demonstration Mass of apparatus and liquids in test tubes Before chemical reaction:____________ After chemical reaction:_____________ What can we conclude? That mass is constant over a chemical reaction.

3. Conservation of Mass The law of conservation of mass states: “In any given chemical reaction, the total mass of the reactants equal the total mass of the products” Where Reactants: Starting substances of a chemical reaction. Products: Created as a result of a chemical reaction.

4. Chemical Equations Chemical equations are used to describe a chemical reaction The simplest form of a chemical equation is the word equation. The general format is: Reactant #1 + Reactant #2 Product #1 + Product #1 “yields”, “to make”, “to produce”

5. Word Equations The chemical equation written using chemical names before using chemical formulas. Examples: Silver Nitrate + Copper  Silver + Copper (II) Nitrate Hydrogen + Oxygen  Water vapour Reactants Products ReactantsProducts

6. Chemical Equations A means of describing a chemical reaction by using chemical formulas. Tip: Remember H O F Br I N Cl These are the diatomic molecules and must be written with two atoms. i.e H 2, O 2, F 2, etc.. In some cases, the state of the reactant or product may be listed: s = solid, aq or l = liquid, g = gas.

7. Example #1 Determine the chemical equation for the following reaction: Lithium reacts with Calcium Chloride to produce Calcium plus Lithium Chloride Li+CaCl 2 CaLiCl+

8. Example #2 Determine the chemical equation for the following reaction: Copper reacts with oxygen gas to make copper (II) oxide Cu+O2O2 CuO

9. Example #3 Determine the chemical equation for the following reaction: Sodium and Chlorine gas react to make Sodium Chloride Na+Cl 2 NaCl

10. Homework P.227 #2,3a,4ac,5a Working with Chemical Equations (web-site)