1. Matt
Chemical Reactions

2. Parts of the Atom Chemical Reaction Basics
What part of the atoms are affected?
Electrons (valence electrons) are affected in reactions because they decide how reactive is the atom.
An atom with one valence electron is more reactive than an atom with seven valence electrons (Figure)
Eight is the most valence electrons in an atom.
These atoms are not reactive.
Electrons are lost or gained in chemical reactions.
Oxidized: Atom loses electrons
Reduced: Atom gains electrons
Figure: Valence Electrons
Gray atom has 1 valence electron
Green atom has 7 valence electrons
Volume Library 1 Chapter 7 page 17 Oxidation-reduction reactions

3. Events during Chemical Rx Chemical Reaction Basics
What is happening during a chemical reaction?
Bonds between atoms or molecules have interactions among their electrons breaking and/or forming new bonds.
Reactants & Products
Application of Law of Conservation of Mass
Five Signs of a Chemical Rx
Description
Reactants which are the substances that go into the reaction come out as final substances called products
No matter what you do to the substance in chemical reactions it will still have the same mass.
Actually law: Matter cannot be created nor destroyed only rearranged.
Five signs:
Change of color
Formation of gas
Formation of precipitate (solid separates for a solution)
Change of temperature
Energy produced
Reference

4. Role of Energy in Chemical Rx
Forms of Energy
Potential Energy– substances have a energy due to electrons and bonds. This is the energy that bonds already have to start with for a reaction.
Activation Energy– threshold energy needed to initiate a chemical Rx or energy requirement to have a chemical reactions. This is the hump need to get over. (On next slide)
Types of Energy Reactions (Table)
Exothermic Rx
Endothermic Rx
Description
Chemical reactions that release energy as part of their product
Chemical reactions that absorb energy to form the product
Basic Concept
A + B  AB + energy
A + B + energy  AB
Example
Combustion of methane CH4 + 2O2  CO2 + 2H2O
Sports “Cold pack” 2NH4NO3(5) + H2O(1) + heat  NH4+(aq) + NO3–(aq)
Graphic 3.

5. Energy and Chemical Reactions
Exothermic reaction
Graphic illustrates that a chemical reaction (x-axis) occurs when a threshold energy is achieved (“activation energy”) and a product is formed that generates heat (ΔH along y-axis)
Endothermic reaction
Figure depicts much energy is needed (y-axis) to “activate” the reaction (x-axis)
Products of this reaction make surrounding area colder due to higher energy needs to activate the reaction

6. Types of Chemical Reactions
Synthesis
Decomposition
Combustion
Single Replacement
Double Replacement
Description
Two substances combine to make a single product
One substance is broken down into two substances
Oxygen is a reactant and products include carbon dioxide & water
One element replaces another as part of a compound
Two compounds “switch partners”
Basic Concept
A + B  AB
AB  A + B
CxHy + O2  CO2 + H20
A + BC  AB + C
AB + YZ  AY + BZ
Example
Iron and sulfur yields iron (II) sulfide
Electrolysis of water to make oxygen and hydrogen gas
Burning of naphthalene
Magnesium replaces hydrogen in water to yield magnesium hydroxide and hydrogen gas
Lead (II) nitrate with potassium iodide forms lead (II) iodide and potassium nitrate
Chemical Formula
8 Fe + S8  8 FeS
2 H2O  2 H2 + O2
C10H O2  10 CO2 + 4 H20
Mg + 2 H20  Mg(OH) 2 + H2
Pb(NO3)2 + 2 KI  PbI2 + 2 KNO3
Video on Chemical Reactions

7. Bibliography
Parts of the Atom Volume Library 1 Chapter 7 page 17 Oxidation-reduction reactions
Events during chemical reaction wiki.answers.com/Q/What_happens_when_a_chemical_reaction_occurs
Role of Energy in Chemical Reactions
Energy and Chemical Reactions
Types of Chemical Reactions