1. Types of Chemical Reactions

2. Exothermic and Endothermic
Chemical reactions involve changes in energy.
All chemical reactions, regardless of what type, can be classified as exothermic or endothermic.

3. Exothermic and Endothermic
Ex- out
Therm- heat
Release heat (and often light) to their surroundings
Temperature goes up
Happens when bonds are formed

4. Examples
Burning
Rusting

5. Exothermic and Endothermic
Endo- in
Therm- heat
Absorbs heat from the surroundings
Temperature goes down
Happens when bonds are broken

6. Examples
Instant cold pack
Baking soda + vinegar
Photosynthesis

7. Synthesis Syn- together
Two or more reactants combine to form one product
A + B  AB

8. Often release heat and light (exothermic)
Synthesis
Often release heat and light (exothermic)

9. Na + Cl  NaCl Sodium + Chlorine  Sodium Chloride
Synthesis
Na + Cl  NaCl Sodium + Chlorine  Sodium Chloride
2 reactants
1 product

10. Other examples: C + O2  CO2 2CaO + H2O  2Ca(OH)2 2CO + O2  2CO2
Synthesis
Other examples:
C + O2  CO2
2CaO + H2O  2Ca(OH)2
2CO + O2  2CO2
2 reactants
1 product

11. One reactant is broken down into two or more products
Decomposition
De-remove; undo
One reactant is broken down into two or more products
(Opposite of a synthesis reaction)
AB  A + B

12. Decomposition
These reactions usually have to absorb heat, light, or electricity to break down the compound.
Heat
Heat

13. 2H2O2  2H2O + O2 Hydrogen Peroxide  Water + Oxygen
Decomposition
2H2O2  2H2O + O2 Hydrogen Peroxide  Water + Oxygen
1 reactant
2 products

14. Other examples: H2CO3  H2O + CO2 2H2O  2H2 + O2 2Al2O3  4Al + 3O2
Decomposition
Other examples:
H2CO3  H2O + CO2
2H2O  2H2 + O2
2Al2O3  4Al + 3O2
1 reactant
2 products

15. Single Replacement
A single element reacts with a compound and takes the place (replaces) of one of the elements in that compound.
The result is a new compound and a new element.
A + BC  B + AC

16. Single Replacement
Usually, similar elements will “replace” each other.
Metals replace metals, nonmetals replace nonmetals, etc.

17. Zn + CuCl2  ZnCl2 + Cu Single Replacement
Zinc + Copper Chloride  Zinc Chloride + Copper
Zinc replaces copper to bond with chlorine
Zinc and Copper are both metals

18. Single Replacement Other examples: Br2 + 2KI  2KBr + I2
Mg + CuSO4  Cu + MgSO4
Bromine replaces Iodine
Magnesium replaces Copper

19. Double Replacement
A reaction between two compounds where one element from each compound switches places.
It is a double replacement because the two elements “replace” each other in the reaction. ds
AB + CD  CB + AD

20. Double Replacement
On the reactant side are two compounds and on the product side are two NEW compounds.
AB + CD  CB + AD

21. 2 compounds  2 new, different compounds
Double Replacement
BaCl2 + MgSO4  MgCl2 + BaSO4
Barium Chloride + Magnesium Sulfate  Magnesium Chloride + Barium Sulfate
2 compounds  2 new, different compounds

22. Double Replacement Other examples: Na2S + 2HCl  2NaCl + H2S
KBr + AgNO3  KNO3 AgBr
Sodium and Hydrogen switch places
Potassium and Silver switch places

23. Combustion
Combustio- to burn
A fuel is combined with oxygen to (usually) produce carbon dioxide and water.
Fuel + O2  CO2 + H2O

24. Combustion
Combustion reactions are also called burning.
Usually occurs at high temperatures.
Releases amounts of heat and light

25. Combustion
Burning of acetylene (used in welding torches) 2C2H2 + 5O2  4CO2 + 2H2O
Oxygen
Carbon
Dioxide
Fuel
Water

26. Combustion Burning Methane CH4 + 2O2  CO2 + 2H2O
Other examples:
Burning Methane
CH4 + 2O2  CO2 + 2H2O
Burning Coal (pure carbon)
C + O2  CO2
Burning Rocket Fuel (pure hydrogen)
2H2 + O2  2H2O

27. Other Types
Oxidation: Reactions where an element or compound loses electrons because of an oxidizing agent (often Oxygen)
Example: Iron rusting, an apple turning brown

28. NaHCO3 + HCl  NaCl + H2O + CO2
Other Types
Acid-Base (Neutralization): An acid and a base react to form water and a salt.
Example: Alka seltzer or Tums are taken to neutralize stomach acid
NaHCO3 + HCl  NaCl + H2O + CO2