1. CHEMICAL REACTIONS
The process by which one or more substances are changed into one or more different substances

2. Word Equations To write a word equation,
1. write the names of the reactants to the left of the arrow separated by plus signs;
2. write the names of the products to the right of the arrow, also separated by plus signs.
Reactant + Reactant  Product + Product

3. EXAMPLE
Methane + Oxygen  Carbon dioxide + Water

4. EXAMPLE 2
iron + oxygen  iron(III) oxide

5. EXAMPLE 3
Hydrogen Peroxide  Water and Oxygen

6. Skeleton Equations
Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.
A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products.
Here is the equation for rusting:
Fe + O2  Fe2O3

7. Catalyst
A catalyst is a substance that speeds up the reaction but is not used up in the reaction
Without catalyst With Catalyst

8. Important Symbols

9. Balancing Chemical Equations
To write a balanced chemical equation,
write the skeleton equation
use coefficients to balance the equation so that it obeys the law of conservation of mass.
Remember you want the same number of atoms of each element on each side of the equation.

10. Example

11. Example 2

12. Example 3 -- Try on your own!!!
Write a balanced chemical equation for the reaction in which sodium hydroxide and calcium bromide react to produce solid calcium hydroxide and sodium bromide. The reaction occurs in water.

13. Summary Reduce coefficients to lowest possible ratio Count atoms
Write a skeleton equation
Count atoms
Add/adjust coefficients
Reduce coefficients to lowest possible ratio
Check your work

14. Synthesis Reactions (Combination)
Two or more reactants produce one product
Examples:
NH3 + HCl  NH4Cl
H O2  H2O
Ag S  Ag2S
Al + Cl2  AlCl3

15. Decomposition One reactant produces two or more products Examples
Ag2O Ag + O2
PCl5  PCl3 + Cl2
H2O2 H2O + O2
CuO Cu + O2

16. Single Replacement One element replaces another element
Must consult the activity series

17. Single Replacement
One element and one compound producing a different element and compound
Examples
Fe + H3(PO4)  H Fe3(PO4)2
H CuO  Cu H2O
Zn HCl  H ZnCl2
Cl KBr  Br KCl

18. Double Replacement
A double-replacement reaction is a chemical change involving an exchange of positive ions between two compounds.
Examples:
Al(NO3) NaOH  Al(OH) NaNO3
PbCl Li2SO4  PbSO LiCl
ZnBr AgNO3  Zn(NO3) AgBr
BaCl KIO3  Ba(IO3) KCl

19. Double replacement
Three main products of a double replacement reaction
Precipitate (solubility table)
Water
Gas

20. Combustion A combustion reaction chemical change
element or a compound reacts with oxygen
producing energy in the form of heat and light

21. Combustion
A hydrocarbon reacts with oxygen to produce carbon dioxide and water Examples: CH4 + O2  CO2 + H2O C6H12O6 + O2  CO2 + H2O

22. Chemical Equations from Names
magnesium and hydrogen chloride produce hydrogen and magnesium chloride
calcium hydroxide and lithium chloride produce lithium hydroxide and calcium chloride
decompose copper (II) oxide into copper and oxygen
aluminum and iron (III) oxide produce iron and aluminum oxide
combustion of butane (C4H10) in air to produce carbon dioxide and water