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New UnitEnergy and Reactions
1. Energy
What is energy?Energy = ability to do work
What is work?Work = TRANSFER of energy from one object to another.
1. Energy
Energy exists in many forms
- Kinetic- Potential- Thermal/Heat- Chemical- Electrical- Electromagnetic/Light- Mechanical- Nuclear- Sound
1. Energy
IMPORTANTEnergy CANNOT be created or
destroyed
1. Energy
IMPORTANTEnergy CANNOT be created or
destroyedEnergy is CONVERTED from one form to
another.
1. Energy
IMPORTANTEnergy CANNOT be created or
destroyedEnergy is CONVERTED from one form to
another.
1. Energy
IMPORTANTEnergy CANNOT be created or
destroyedEnergy is CONVERTED from one form to
another.
1. Energy
IMPORTANTEnergy CANNOT be created or
destroyedEnergy is CONVERTED from one form to
another.
1. EnergyIn this class: changes in bond energy in reactions
and physical changes
1. Energy
1. Explain the conservation of energy
2. Why might a one-step energy conversion be preferred over a two-step conversion?
2. Physical vs Chemical Changes
2. Physical Changes and Reactions
How is a physical change different from a chemical change?
Physical Chemical
Example:Changing outfits Changing DNA
2. Physical Changes and ReactionsSigns of a chemical change
1.Evolution of a gas2.Formation of something solid3.Change in appearance4.Change in energy
2. Physical Changes and Reactions
Both physical and chemical changes need energy or release energy
Add energy to ice = waterIce melts = water and releases energy
2. Physical Changes and Reactions
Both physical and chemical changes need energy or release energy
Add energy to matchMatch burns = releases energy as fire
2. Physical Changes and Reactions
Endothermic
Exothermicabsorbs/needs energy releases energy
2. Physical Changes and Reactions
Show chemical changes with equations
Reactants Products
means “produces”
2. Physical Changes and Reactions
Writing Reactions
Baking soda, NaHCO3 combines with acetic acid,
HC2H3O2 to produce sodium acetate NaC2H3O2,
carbon dioxide CO2, and water H2O.
Page 266 # 1,3,4,5,9,10,11,12
3. Types of Reactions
5 main categories
SynthesisDecomposition
CombustionSingle ReplacementDouble Replacement
3. Types of Reactions
Combustion
Explanation: something with carbon + oxygen
Example: C6H12O6 + 6O2 6CO2 + 6H2O
Pattern: Carbon + O2 CO2 + H2O
3. Types of Reactions
SynthesisExplanation: when two or more
become one
Example: H2 + O2 2H2O
Pattern: A + B AB
3. Types of Reactions
Decomposition
Explanation: when one becomes two
or more/breakup
Example: 2H2O H2 + O2
Pattern: AB A + B
3. Types of Reactions
Single Replacement
Explanation: Love Triangle
Example: Zn + CuSO4 Cu + ZnSO4
Pattern: A + BC B + AC
3. Types of Reactions
Double Replacement
Explanation: Soap Opera Drama
Example:KCl+ NaNO2 NaCl + KNO2
Pattern: AB + CD AD + BC
4. Balancing Reactions
OBJECTIVE: Applying
Conservation of Mass to Reactions
4. Balancing Reactions
Conservation of Mass: cannot create or destroy
mass
this means:there needs to be the same number of atoms on both
sides of reaction
4. Balancing Reactions
frame + wheels + chain + handlebars + pedals 1 bicycle
1 frame + 2 wheels + 1 chain + 1 handlebar + 2 pedals
1bicycle
What are those numbers?
COEFFICIENTS
4. Balancing Reactions
H2 + O2 H2O
4. Balancing Reactions
H2 + O2 2H2O
4. Balancing Reactions
2H2 + O2 2H2O
4. Balancing Reactions
2H2 + O2 2H2O
NEVER change
subscripts
4. Balancing Reactions
2H2 + O2 2H2OCH4 + 2O2 CO2 + 2H2O
Cu + 2AgNO3 2Ag + Cu(NO3)2
2KI + Pb(NO3)2 PbI2 + 2KNO3
What are those numbers?
COEFFICIENTS
4. Balancing ReactionsStrategy for Balancing Reactions
1. Start with compound2. Add coefficients to balance 3. Leave single elements, like O2, H2, Al, Cu, etc.
for last.4. Use fractions if necessary. 5. Simplify if necessary. If fractions used, simplify
fractions as well. 6. Check work.
NEVER CHANGE SUBSCRIPTS! DO NOT SPLIT COMPOUNDS!
A) Identify type of rxn B) Balance
1. Na + O2 Na2O2
2. Al + S8 Al2S3
3. O2 + C6H12O6 CO2 + H2O
4. Na + NaNO3 Na2O + N2
5. H3PO4 + KOH K3PO4 + H2O
6. NH3 + O2 N2 + H2O
4. Balancing ReactionsBalancing Reactions with Polyatomic Ions
Mg + OH- Mg(OH)2
HgCl2 + AgNO3 Hg(NO3)2 +AgCl
Al + Hg(CH3COO)2 Al(CH3COO)3 + Hg
A) Identify type of rxn B) Balance
1. C2H6 + O2 CO2 + H2O
2. Al + HAsO3 H2 + Al(AsO3) 3
3. H3PO4 + Mg(OH) 2 Mg3 (PO4) 2 + H2O
4. NH4OH + H3PO4 (NH4)3PO4 + H2O
5. Al(OH)3 + H2SO4 Al2(SO4)3 + H2O
6. C10H22 + O2 CO2 + H2O (fractions?)
4. Balancing Reactions
How are coefficients different from subscripts?
2H2 + O2 2H2O
subscripts = # of atoms
4. Balancing ReactionsHow are coefficients different from subscripts?
2H2 + O2 2H2O
coefficients = how many
4. Balancing Reactions
2H2 + O2 2H2O
subscripts = # of atomscoefficients = how many
4. Balancing Reactions
H2 + O2 H2O2
subscripts = # of atomscoefficients = how many
End of Chapter 8
Topics Covered
1.Energy2.Physical vs. Chemical Changes3.Types of Reactions4.Balancing Reactions
Sample Problem
Methane, CH4, reacts with O2 to combust and produce the following: CO2 and H2O. This reaction results in the release of a large amount of energy.
1. Write a balanced reaction.2. This is what type of reaction?3. This reaction resulted in 49.1 grams of CO2. This is
equal to how many moles?4. CH4 is a covalent compound. Draw its Lewis
Structure
