1. Chemical Reactions

2. Chemical Change
Physical Change

3. Chemical Change Reactants Products Signs of a chemical change
Color change
Production of a gas
Formation of a precipitate
Energy change
Exothermic vs. endothermic
Occurs as bonds are broken or formed

4. Chemical Formulas
Shows the number of atoms of each element in a compound
Subscripts below the symbol indicate the number of atoms
Use the distributive property for subscripts outside parentheses
Determine the number of each type of atom in the following compounds
H2O (NH4)3PO4
C12H22O Pb(ClO3)4
Ca(CO3) Ba3(AsO4)2

5. Chemical Formulas: Covalent Compounds
Number of atoms
Prefix 1
mono- (not used for first element) 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona-
Prefixes indicating the number of each atom are used in naming molecules
Ex:
carbon tetrachloride
P2O5 CO
dinitrogen trioxide
dinitrogen pentoxide
S3Cl7

6. Chemical Formulas: Covalent Compounds
Write the prefix for the number indicated. 9 7 8 6
Write the name or the formula.
NO 8. dinitrogen tetroxide
SiO sulfur hexafluoride
P3Cl dihydrogen monoxide

7. Chemical Formulas: Ionic Compounds
To write the formula:
Determine the charge on the ions using the PT.
Some charges are written on transition metals
Balance the charges to make a neutral compound.
Add subscripts to indicate the number of each element.
Examples:
barium fluoride
aluminum oxide
Do “Forming Compounds”

8. Chemical Equations Reactions are written for chemical changes
Use correct chemical formulas
Reactants Products
Due to the Law of Conservation of Mass, the number of atoms of each element on the reactant side = number of atoms of each element on the product side
Use coefficients to balance equations
Do not change subscripts (they’re determined by neutralizing charges when writing formulas)
Use “balancing chemical equations” handout

9. Reaction Types Synthesis- makes one product
__________ + _________ _________
A + B AB
AB + C ABC
Decomposition- one reactant
_________ __________ + _________
ABC AC + B
AB A + B
(How are synthesis and decomposition related?)
Use paper clips!

10. Reaction Types
Single Replacement- one element replaces another that is in a compound
Element + compound compound + element
_______ + ______ _____ + _____
AB + C A + CB
AB + C AC + B
Double Replacement- 2 compounds switch ions
Compound + compound compound + compound
AB + CD AD + CB
Positive ions are always written 1st !