New Unit Energy and Reactions. 1. Energy What is energy? Energy = ability to do work What is work?...

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