1. Friday 1/20
List the different elements in the chemical reaction. How many of each do you have on each side?
Why do you think that is?

2. Reaction Types and Balancing

3. Essential Questions: Chemical Reactions
What is a chemical reaction?
How do we know when they happen?
How do we communicate about them?
Why must we balance chemical equations?

4. What is a chemical reaction?
The process by which the atoms of one or more substances are rearranged to form different substances.
Example: 2H2O H2 + O2
A chemical change
Chemical bonds are broken or made

5. How do we know when a chemical reaction has happened?
Evidence!
There are 4 major indicators of
chemical change.
Temperature change
Color change
Gas production (odor, bubbles)
Solid formation

6. How do we communicate about chemical reactions?
Sentences
Solid carbon disulfide reacts with oxygen gas, producing carbon dioxide gas and sulfur dioxide gas.
Word Equations
carbon disulfide (s) + oxygen (g) → carbon dioxide (g) + sulfur dioxide (g)
Chemical Equations
CS2 (s) + O2 (g) → CO2 (g) + SO2 (g)

7. Chemical Equations
Symbols to indicate the state of reactants and products:
(g) gas
(l) liquid
(s) solid
(aq) aqueous
Δ (over arrow)
It means: requires heat
Other symbols:
+ : Must be included between each distinct reactant or product
→: Means “to yield”
separates reactants from products

8. Reactants vs. Products
In a chemical reaction, reactants are chemically combined or broken down to make (produce) products .
arrow always points toward products!
reactants
products

9. Writing and Balancing Equations
Chemical equations need to be balanced to comply the Law of Conservation of Mass
matter cannot be created or destroyed
# of atoms for each element must = each other on both sides of rxn.
** use coefficients (moles) to balance.
-Coefficients are the large # in front of compound
- must be whole numbers start from far left and work your way to the right!

10. cont… Are the following equations balanced? 2 2 2 4 2
H2O2 (aq) O2 (g) H2O (l) 2
2AgNO H2S Ag2S HNO3 2 4
MnO HCl MnCl H2O + Cl2 2

11. Types of Reactions 2 2 2 2 Mg (s) + O2 (g) MgO (s)
There are five different types of reactions…
- synthesis, decomposition, single displacement, double displacement, combustion
SYNTHESIS…
- two or more reactants combine to produce one product.
Ex… 2
Mg (s) + O2 (g) MgO (s) 2
CaO (s) + CO2 (g) CaCO3 (s) 2
KNO2 (s) + O2 (g) KNO3 (s) 2

12. 2 2 2 HgO Hg + O2 HNO3 N2O5 + H2O DECOMPOSITION…
- opposite of synthesis
- one reactant breaks down (decomposes) into two or more products.
Ex… 2
HgO Hg O2 2 2
HNO N2O H2O

13. 2 2 Mg + Zn(NO3)2 Mg(NO3)2 + Zn Cl2 + KI KCl + I2 SINGLE DISPLACEMENT…
- one element in a compound is displaced (kicked out) by another (more reactive) element .
- reactants =1element &1compound …products = 1element & 1 compound.
Ex…
Mg + Zn(NO3)2
Mg(NO3)2 + Zn
Cl KI 2 2
KCl + I2
** metals can only replace metals and vice versa for non-metals!

14. 3 2 6 NaCl + AgNO3 AgCl + NaNO3 Ca(OH)2 + H3PO4 H(OH) + Ca3(PO4)2
DOUBLE DISPLACEMENT…
- cations of two different compounds trade places.
- reactants = 2 compounds …products = 2 different compounds
Ex…
NaCl + AgNO3
AgCl + NaNO3 3
Ca(OH)2 + H3PO4 2 6
H(OH) + Ca3(PO4)2
(H2O)

15. 5 3 4 6 6 6 C3H8 + O2 CO2 + H2O C6H12O6 + O2 CO2 + H2O COMBUSTION…
- generally involves the burning of a hydrocarbon.
- fires generally need oxygen to burn (reactant).
- fires generally release water and carbon dioxide (products).
- reactants = hydrocarbon and O2 …products = H2O and CO2
Ex…
C3H O CO H2O 5 3 4
C6H12O O CO H2O 6 6 6

16. identify the following types of rxns…
Pb(NO3)2 + K2CrO4
PbCrO4 + 2KNO3
double displacement
2Al(OH)3
Al2O3 + 3H2O
decomposition
CH4 + 2O2
CO2 + 2H2O
combustion
4Li + O2
2Li2O
synthesis
2Al + 3CuSO4
Al2(SO4) Cu
single displacement