1. Ch. 8 – Chemical Equations & Reactions

2. Describing Chemical Reactions
Process by which one or more substances are changed into one or more different substances
Chemical equation- represents with symbols & formulas identities and amounts of reactants and products

3. All Chemical Reactions
have two parts
Reactants - the substances you start with
Products- the substances you end up with
The reactants turn into the products.
Reactants ® Products

4. Chemical Equations
A+B  C+D
REACTANTS
PRODUCTS

5. Chemical Equation Click below to watch the Visual Concept.

6. Law of Conservation of Mass
mass is neither created nor destroyed in a chemical reaction
total mass stays the same
atoms can only rearrange
4 H
2 O
4 H
2 O
36 g
4 g
32 g
C. Johannesson

7. Signs of a Chemical Reaction
Creation of heat and light
Formation of a gas
Formation of a precipitate – solid produced and separated from a solution
Color change

8. Signs of a Chemical Reaction
Click below to watch the Visual Concept.
Visual Concept

9. Chapter 8 Characteristics of Chemical Equations, continued
Section 1 Describing Chemical Reactions
Chapter 8
Characteristics of Chemical Equations, continued
Additional Symbols Used in Chemical Equations

10. Chapter 8 Characteristics of Chemical Equations, continued
Section 1 Describing Chemical Reactions
Chapter 8
Characteristics of Chemical Equations, continued
Additional Symbols Used in Chemical Equations

11. Symbols Used in Chemical Equations
Click below to watch the Visual Concept.
Visual Concept

12. 2H2(g) + O2(g)  2H2O(g) Writing Equations
Identify the substances involved.
Use symbols to show:
How many? - coefficient
Of what? - chemical formula
In what state? - physical state

13. Describing Equations 3CO2  2Mg  4MgO 
Describing Coefficients:
individual atom = “atom”
covalent substance = “molecule”
ionic substance = “unit”
3CO2 
2Mg 
4MgO 
3 molecules/MOLES of carbon dioxide
2 atoms/MOLES of magnesium
4 units/MOLES of magnesium oxide

14. Interpreting Chemical Equations
Click below to watch the Visual Concept.
Visual Concept

15. DAY 3
Ch. 8 – Chemical Equations & Reactions

16. Synthesis
the combination of 2 or more substances to form a compound
only one product
A + B  AB

17. Synthesis Reactions Click below to watch the Visual Concept.

18. Decomposition
a compound breaks down into 2 or more simpler substances
only one reactant
AB  A + B

19. Electrolysis
Click below to watch the Visual Concept.
Visual Concept

20. A + BC  B + AC Single Replacement
one element replaces another in a compound
Reactants must be an element and a compound.
metal replaces metal (+)
nonmetal replaces nonmetal (-)
A + BC  B + AC
C. Johannesson

21. AB + CD  AD + CB Double Replacement Two things replace each other.
Reactants must be two ionic compounds or acids.
ions in two compounds “change partners”
cation of one compound combines with anion of the other
AB + CD  AD + CB
C. Johannesson

22. E. Double Replacement Pb(NO3)2(aq)+ KI(aq)  2 2 PbI2(s)+ KNO3(aq)
Products:
switch negative ions
one product must be insoluble
Pb(NO3)2(aq)+ KI(aq) 
PbI2(s)+ KNO3(aq)
NaNO3(aq)+ KI(aq) 
N.R.

23. Types of Reactions: Combustion
the burning of any substance in O2 to produce heat
A + O2  B
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

24. Combustion 4 2 Na(s)+ O2(g)  Na2O(s) C3H8(g)+ O2(g)  5 3 4
Products:
contain oxygen
hydrocarbons form CO2 + H2O
Na(s)+ O2(g) 
Na2O(s)
C3H8(g)+ O2(g) 
CO2(g)+ H2O(g)

25. Combustion Reaction Click below to watch the Visual Concept.

26. DAY 4
Ch. 8 – Chemical Equations & Reactions

27. 2H2(l) + O2(l)  2H2O(g) + energy
B. Exothermic Reaction
reaction that releases energy
products have lower PE than reactants
energy released
2H2(l) + O2(l)  2H2O(g) + energy

28. C. Endothermic Reaction
reaction that absorbs energy
reactants have lower PE than products
energy absorbed
2Al2O3 + energy  4Al + 3O2

29. Activity Series Activity- ability of an element to react
Activity Series- list of elements organized according to the ease with which they undergo certain reactions
Metals greater activity greater ease of loss of electrons (cations)
Nonmetals greater activity greater ease of gain of electrons (anions)

30. Activity Series of the Elements

31. Activity Series Click below to watch the Visual Concept.

32. Ch. 17 – Chemical Reactions
V. Reaction Rate (p )

33. A. Collision Theory
In order for reactions to occur depends on the collisions between reacting particles.
Successful collisions occur if the particles...
collide with each other
have the correct orientation
have enough kinetic energy to break bonds

34. A. Collision Theory Particle Orientation Required Orientation
Unsuccessful Collisions
Successful Collision

35. A. Collision Theory Activation Energy (Ea)
minimum energy required for a reaction to occur
Barrier between reactants and products
Activation
Energy

36. A. Collision Theory Activation Energy depends on reactants
low Ea = fast rxn rate Ea

37. B. Factors Affecting Rxn Rate
Surface Area
high SA = fast rxn rate
more opportunities for collisions
Increase surface area by…
using smaller particles
dissolving in water

38. B. Factors Affecting Rxn Rate
Concentration
high conc = fast rxn rate
more opportunities for collisions

39. B. Factors Affecting Rxn Rate
Temperature
high temp = fast rxn rate
high KE
fast-moving particles
more likely to reach activation energy

40. B. Factors Affecting Rxn Rate
Catalyst
substance that increases rxn rate without being consumed in the rxn
lowers the activation energy

41. B. Factors Affecting Rxn Rate
Enzyme Catalysis