Understanding Chemical Changes: Equations and Laws

1. Chemistry 11.1 “Describing Chemical Changes”

2. Review A. Reactants  Products B. Dalton’s Theory… “As reactants are converted to products, the bonds holding the atoms together are broken and new bonds are formed.” C. Law of Conservation of Mass… “Mass is neither created nor destroyed.”

3. II. Equations A. Word Equations 1. Def – words used to describe a chemical reaction. -no #’s are involved 2. Ex: Iron + Oxygen  Iron (III) Oxide 3. Ex: Hydrogen Peroxide  Water + Oxygen 4. Ex: Methane + Oxygen  Carbon Dioxide + water

4. 5. What is the word equation for…Pure copper can be produced by heating copper (II) sulfide in the presence of diatomic oxygen from the air. Sulfur dioxide gas is also a product in this reaction. Copper II Sulfide + Oxygen  Copper + Sulfur Dioxide

5. B. Chemical Equations 1. Def – Using chemical symbols to write a chemical formula. - #’s are involved 2. Ex: Fe + O2 Fe2O3 -this is a skeleton equation b/c it is not balanced

6. C. Balanced Chemical Equations 1. Follows the Law of Conservation of Mass. 2. 4 Fe + 3 O22 Fe2O3

7. III. Symbols used in chemical equations