1. Chapter 7 Notes
Chemical Reactions

2. Chapter 7.1 Describing Reactions
Reactants –
substances that undergo change
Products –
new substances formed as a result of that change
Reactants  Products

3. Chapter 7.1 Describing Reactions
Chemical Equation –
representation of a chemical reaction in which the reactants and products are expressed as formulas.
Ex) C + O2  CO2

4. Burning of Carbon
Figure 2

5. Burning of Carbon
Figure 2

6. Burning of Carbon
Figure 2

7. Chapter 7.1 Describing Reactions
Law of Conservation of Mass –
mass cannot be created or destroyed in a chemical equation; it can only change form

8. Chapter 7.1 Describing Reactions
In order to show that mass is conserved during a reaction, a chemical equation must be BALANCED (same # of atoms of each element on both sides)
Coefficient –
number written before the formulas
change these to balance equation
NEVER change subscripts

9. Balancing Practice 2
N=2
H=4
O=2
N=2
H=4
O=2

10. More Balancing Problems2 2 4 2 2 2 2 4 3

11. Chapter 7.2 Types of Reactions
Synthesis –
two or more substances react to form a single substance

12. Chapter 7.2 Types of Reactions
Decomposition –
a compound breaks down into two or more simpler substances

13. Chapter 7.2 Types of Reactions
Single Replacement –
one element takes the place of another element in a compound
AB + C  AC + B p.202

14. Chapter 7.2 Types of Reactions
Double Replacement –
two different compound exchange positive ions and form two new compounds
AB + CD  AD + CB p. 203

15. Models of Reactions
The following drawings represent reactants and products of three different chemical reactions.
1. Synthesis means “putting something together.” Which drawing represents a synthesis reaction? Explain your answer.

16. Models of Reactions
The following drawings represent reactants and products of three different chemical reactions.
2. Decomposition means “taking something apart.” Which drawing represents a decomposition reaction? Explain your answer.

17. Models of Reactions
The following drawings represent reactants and products of three different chemical reactions.
3. Replacement means “something taking the place of another.” Which drawing represents a replacement reaction? Explain your answer.

18. Chapter 7.2 Notes Types of Reactions
Other types of Reactions:
Combustion –
a substance reacts rapidly with oxygen, producing heat and light
Oxidation-Reduction (Redox) –
electrons are transferred from one reactant to another
Oxidation –
process in which an element loses electrons during a chemical reaction
Reduction –
process in which an element gains an electrons during a chemical reaction

19. Chapter 7.2 Notes Types of Reactions
Chemical Energy –
energy stored in the chemical bonds of a substance
Breaking Bonds = required energy
Forming Bonds = released energy
Exothermic Reaction –
releases energy to its surrounding – formation of bonds
Endothermic Reaction –
absorbs energy from its surroundings – breaking of bonds

20. What type of reaction is this?

21. What type of reaction is this?

22. What type of reaction is this?

23. What type of reaction is this?

24. Chapter 7.2 Notes Types of Reactions
Law of Conservation of Energy –
energy cannot be created or destroyed; it can only change form
The amount of energy in the universe is constant.
Activation Energy –
The amount of energy required to start a chemical reaction.

25. Chapter 7.3 Notes Types of Reactions
Reaction Rate –
rate at which reactants change into products over time
Factors that affect reaction rates:
1. Temperature
increase the temperature, the reaction rate will increase; the opposite is also true
2. Surface Area
increase surface area, the reaction rate will increase
3. Stirring
if you stir something, it will react faster

26. Chapter 7.2 Notes Types of Reactions
Factors that affect reaction rates (Cont):
4. Concentration
if you increase the concentration, the reaction rate will increase
5. Catalyst –
speeds up chemical reactions without taking part in the reaction itself
Ex) enzymes that speed up digestion
6. Inhibitors -
slows down or stops chemical reactions from happening
Ex) preservatives in food
Rates of reaction video

27. Chapter 7.2 Notes Types of Reactions
Factors that affect reaction rates (Cont):
5. Catalyst –
Which reaction requires the least amount of energy to activate?

28. Chapter 7.2 Notes Types of Reactions
Equilibrium –
a state in which the forward and reverse paths of a change take place at the same rate
Physical equilibrium –
both forward and reverse changes occur simultaneously
Ex) water condensing and
evaporating at the same rate

29. Chapter 7.2 Notes Types of Reactions
Reversible reaction –
reaction in which the conversion of reactants into products and the conversion of products into reactants can happen at the same time
Chemical equilibrium –
forward and reverse chemical changes occur simultaneously
Factors affecting chemical equilibrium:
Temperature
Pressure
Concentration

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