1. Observing Chemical Change
Chapter 6 Section 1 Pg
Reactant atoms and molecules interact to form products with different chemical properties. 5a
Chemical reactions usually liberate heat or absorb heat. 5c

2. Intro to chemical reactions

3. Physical Change Chemical Change
What is the difference between chemical and physical changes?
Stop and
Think???
Physical Change Chemical Change

4. Stop and
Think???
Using a marshmallow give an example of a physical and a chemical change.
Physical Change
Chemical Change

5. Reaction of MgO
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6. Magnesium reacting with Oxygen
During a chemical change bonds break and new bonds form.
What type of bond is this? 1 O O
Magnesium reacting with Oxygen Mg + 2 Mg O 2+ 2-
Reactants
Products 5a 5c

7. Forms a Precipitate (a solid)
List 4 ways to help determine that a Chemical reaction has occurred?
Color Change
Forms a Precipitate (a solid)
Gas Formation
Temp. Change 5a 5c

8. Chemical reaction

9. Energy went into breaking the bonds Endothermic
Changes in Energy
Breaking bonds requires energy. An endothermic reaction absorbs energy.
Energy went into breaking the bonds Endothermic
Energy Absorbed 5c
Time

10. Energy was released during the formation of the bonds, Exothermic
Changes in Energy
Making bonds releases energy. An exothermic reaction releases energy in the form of heat.
Energy was released during the formation of the bonds, Exothermic
Energy Absorbed 5c
Time

11. Overall energy was released, Exothermic
Changes in Energy
The formation of water from oxygen and hydrogen gas is exothermic.
Overall energy was released, Exothermic
Energy Absorbed 5c
Time

12. Energy is absorbed, Endothermic
Determine whether the following are examples of endothermic or exothermic change?
1. Frying an egg will turn the egg whites from a clear liquid into a white solid.
Notes
Energy is absorbed, Endothermic 5c

13. Energy is released, Exothermic
Determine whether the following are examples of endothermic or exothermic change?
2. A log burning in a fireplace.
Notes
Energy is released, Exothermic 5c

14. Energy is absorbed, Endothermic
Determine whether the following are examples of endothermic or exothermic change?
3. The ice pack cools instantly when squeezed causing the chemical within to react.
Notes
Energy is absorbed, Endothermic 5c

15. Video liberating/absorbing heat
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16. Describing Chemical Reactions
Chapter 6 Section 2 Pg
Reactant atoms and molecules interact to form products with different chemical properties. 5a
The idea of atoms explains the conservation of matter: in chemical reactions the number of atoms and their total mass remains the same. 5b 5c
Chemical reactions usually liberate heat or absorb heat.

17. Iron reacts with oxygen to produce iron oxide.
Chemical Equations
All chemical equations use formulas or symbols to represent the substances involved in a reaction.
Iron reacts with oxygen to produce iron oxide.
Fe Iron
55.85 26
O Oxygen
16.00 8
2Fe
+ 3O 
Fe O 2 3 ? ? ? ? 5a

18. Conservation of Matter- matter cannot be created or destroyed.
In a chemical reaction, the number of atoms stays the same no matter how they are arranged. So their mass remains the same.
2Fe
+ 3O 
Fe O 2 3
115 g
50 g
165 g
Reactants
Products 5a 5b

19. Naming and balancing

20. A. At least one solid product will form from ….this reaction.
Two solids and two liquids are mixed together, and a chemical reaction occurs. Which of these statements must be true?
Solve
A. At least one solid product will form from ….this reaction.
B. The two solids will form a new solid, and …. the two liquids will form a new liquid.
C. None of the products will have any of the …. atoms of the reactants.
D. The final result will have the same number …. and type of atoms as the reactants. 5b

21. Balancing Chemical Equations
To describe a reaction accurately a chemical equation must show the same number of each type of atom on both sides of the equation.
Write the equation 1 Mg
+ O 
MgO 2
Count the Atoms 2 Mg
+ O 
MgO 2 1 2 1 1 5b

22. Balancing Chemical Equations
Use Coefficients to Balance the Atoms 3 Mg
+ O 
MgO 2 1 2 2 2 2 Mg
+ O 
MgO 2 1 2
Look back and Check 4 5b

23. Balance the equations below
Solve
Write the equation 1
Count the atoms 2
Use coefficients to balance the atoms 3
Look back and check 4 2
H + O  H O 2 2 4 2 2 2 4 1 2
F NaCl  NaF + Cl 2 2 2 2 1 2 1 2 1 2 1 2 2 2
KClO  KCl O 3 2 2 3 2 2 1 1 2 6 3 2 1 1 2 4 6 2 5b

24. Classifying Chemical Reactions
Review -There are three general types of reactions: synthesis, decomposition, and replacement.

25. 2 SO2 + O2 2 SO3 Classifying Chemical Reactions Synthesis Reaction
NOTES
When two or more elements or compounds combine to form a more complex substance, the reaction is classified as a synthesis.
2 SO2 + O2
2 SO3 5b

26. 2 H2O + O2 2 H2O2 Classifying Chemical Reactions
Decomposition Reaction
NOTES
Decomposition occurs when compounds break down into simpler products
2 H2O + O2
2 H2O2 5b

27. + + FeS + 2 HCl FeCl2 + H2S Classifying Chemical Reactions
Replacement Reaction + +
NOTES
When elements either replace or trade places the reaction is classified as Replacement
FeS HCl
FeCl2 + H2S 5b

28. MgO + 2HBr  MgBr2 + H2O 2N2 + 5O2  2N2O5 2Al2O3  4Al + 3O2
Determine whether the following are: synthesis, decomposition, or replacement.
MgO + 2HBr  MgBr2 + H2O
(Replacement)
2N2 + 5O2  2N2O5
(Synthesis)
2Al2O3  4Al + 3O2
(Decomposition) 5b