1. 8.1 NOTES Chemical Equations

2. I. Reactions and Equations
A. Evidence of chemical reactions process by which atoms are rearranged
Evidence of a chemical change:
temperature change
color change,
odor
gas bubbles
and/or formation of a precipitate;
a metal turning shiny does not indicate a chemical change
i.e. penny in acid – penny does not react but is cleaned up so appears shinier
In a chemical change, atoms must be rearranged, but atoms and mass are conserved.

3. B. Representing chemical reactions
1. Word equations - words are used to describe what is occurring in a chemical reaction rather than formulas
- states are used b/c can give important clues to describe what is happening
- reactants go into a rxn and products come out of a rxn

4. - (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous;
+ separates two or more reactants/products;
 separates reactants from products;
- common states should know: H2, Cl2, F2, CO2, H2S (gases), metals are all solids with the exception of Hg, Br2 and Hg are liquids; I2 = solid; solutions = aqueous

5. 2. Skeleton equations - uses chemical formulas in place of words; continues to show states of reactants or products; not as cumbersome
- fails to show how the conservation of mass is followed;

6. 3. Chemical equations - accurately represents a chemical reaction
- observes the law of conservation; states are shown; statement that uses chemical formulas to show the identities and relative amounts of the substances involved;

7. C. Balancing chemical equations
Coefficient - number written in front of a reactant or a product; can change
indicates the # of molecules or moles needed to react
i.e. 2 moles/molecules of H2 react w/ 1 mole/molecule O2  2 moles/molecules H2O
REMEMBER that formulas can NEVER change

8. Al Br  AlBr3
2Al Br  AlBr3

9. NaOH  Na2O + H2O
2NaOH  Na2O + H2O

10. C4H10 + O2  CO2 + H2O
C4H O2  4CO2 + 5H2O
2C4H O2  8CO H2O

11. Fe + H2O  Fe3O4 + H2
3Fe + 4H2O  Fe3O4 + 4H2

12. Al2(SO4)3 + Ba(NO3)2  BaSO4 + Al(NO3)3