Transcript Types of Chemical Reactions - Mrs. Haynie's 8th Grade

Bell Ringer
11-9-09
1. A change in a substance that does not change the substance’s identity is a
_________ change.
2. What is an example of #1?
3. A change in a substance that causes that substance to break and form a new
substance is a ________ change.
4. What is an example of #3?
ALCOS Objectives:
#1-
Identify the steps of the scientific method
#4 State the law of conservation of matter
(Balancing Chemical Equations)
Types of Chemical Reactions
Types of Chemical Reactions

1. SYNTHESIS – two or more substances combine to form
one compound

Example: 2 Mg + O 2 -----> 2 MgO

2. DECOMPOSITION – One substance breaks down into 2
or more elements or compounds

Example: 2 H20 --- 2 H2 + 0 2

3. REPLACEMENT OR DISPLACEMENT reactions- When
one or more elements replace one another

Ex: Zn + 2 HCl ---- ZnCl2 + H2
Copy and tell if it is a synthesis, decomposition, or
displacement
 1.
 2.
 3,
 4.
 5.
2CO + O2 ---- 2CO2
4Fe + 3O2 --- 2 Fe2O2
2H2O2 ---- 2H2O + O2
2KBr + Cl2 ---- 2KCl + Br2
C6H6 + Cl2--- C6H5Cl + HCl
 6.
 7.
Zn Cl2 ----> Zn + Cl2
4H2 + Fe3O4 -- 3Fe + 4H2O
 8. AgNO3 + NaCl -- AgCl + Na NO3
 9. Mg + 2HCl -- MgCl2 + H2
Endothermic and Exothermic Reactions
 Exothermic
Reactions
 1. the burning of carbon
C
 2.
+ O2 ---- CO2 + energy
the formation of salt
 Na
+ Cl --- NaCl + energy
Endothermic Reactions

Photosynthesis in plants


6CO2 + 6H20 + energy -- C6H12O6 + O2
The breakdown of water into hydrogen and oxygen

2H2O + energy ---- 2H2 + O2
Choose endothermic or exothermic for each example:

1.
 2.
 3.
 4.
 5.
 6.
oil is burned
an electric eel shocks its prey
a cake bakes
someone strikes a match
a flashbulb flashes on a camera
dead plant material decays, producing warm compost

7. fireworks explode
 8. clay turns into brick when it is heated in a kiln at high
temperatures
 9. chemical reactions occur in a battery
 10. a firefly flashes its light
Answer key:
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1. exo.
2. exo.
3. endo.
4. exo.
5. exo.
6. exo.
7. exo.
8. endo.
9. exo.
10. exo.