1. Chemical Equations & Reactions Materials: Conserving Matter

2. Chemical Reaction Process by which one or more substances are changed into one or more different substances

3. Indications of a Chemical Reaction 1. Evolution of heat & light

4. Indications of a Chemical Reaction 2. Production of a gas

5. Indications of a Chemical Reaction 3. Formation of a precipitate

6. Indications of a chemical reaction 4. Change in color. (sumac leaves change color when chlorophyll is destroyed)

7. Chemical Reactions There are many ways where matter seems to disappear: The consumption of fuel by your car. The lunch you ate today. The rusting away of your car. Do they really disappear? NO

8. Chemical Equation Reactants  Products Follows the Law of Conservation of Mass

9. Chemical Reactions Law of Conservation of Matter: in a chemical reaction, matter in neither created nor destroyed; the molecules are merely rearranged atoms are forever! you should be able to account for every individual atom in a chemical reaction

10. Word Equation Represents facts- only qualitative Example: Methane + oxygen  carbon dioxide + water Writing Chemical Equations

11. Example: CH 4(g) + O 2(g)  CO 2(g) + H 2 O (g) (not balanced) Symbols you will see in equations Formula Equation Writing Chemical Equations

12. Inserting Coefficients-small whole # that appears in front of a formula Multiplies number of atoms of each element indicated in chemical formula Example: CH 4(g) + 2O 2(g)  CO 2(g) + 2H 2 O (g) Balanced Formula Equation Writing Chemical Equations

13. Atom Inventory Name the number and type of atoms in AgNO 3 (NH 4 ) 2 CO 3 6 H 2 O

14. Atom Inventory In order to follow the law of conservation- there must be the same number and type of atoms on both sides of the equation.

15. Atom Inventory Is this equation balanced? Take an atom inventory Mg + O 2  MgO yes no 2NaOH  Na 2 O + H 2 O yes no Mg + Cl 2  MgCl 2 yes no

16. Balancing Chemical Equations Balance the formula equation according to the law of conservation of mass Balance the different types of atoms one at a time Balance polyatomic ions that appear on both sides of the equation as single units Balance H atoms and O atoms after atoms of all other elements have been balanced

17. Examples Mg + HCl  MgCl 2 + H 2 Al 2 (SO 4 ) 3 + Ca(OH) 2  Al(OH) 3 + CaSO 4 MgI 2 + KNO 3  KI + Mg(NO 3 ) 2