1. Chemical Reactions

2. How Do We Know a Reaction Has Taken Place?
There are often clues that let us know when a chemical reaction is taking place.
Let’s do a lab to find out what some of these clues are.
Some clues are:
Gets hot (exothermic)
Gets cold (endothermic)
Releases gas (bubbles)
Color change
Smell change

3. Reactions Can Occur at Different Speeds
How do the following affect the rate of a reaction?
Temperature?
Concentration?
Surface Area?
Let’s do a lab to find out!

4. As the temperature increases, the reaction occurs faster.
This occurs because the molecules are moving faster, and “run” into each other sooner
As the concentration decreases, the reaction occurs slower.
This occurs because there are less molecules to “run” into
As the surface area increases, the reaction occurs faster.
This occurs because there are more exposed atoms to react with.

5. There are 5 Main Types of Reactions
Synthesis (Composition)
Decomposition
Single Replacement (Displacement)
Double Replacement (Displacement)
Combustion

6. Synthesis
When two or more substances combine to form a single substance
A + B  AB
2H2 + O2  2H2O

7. Decomposition One compound is broken down into two or more substances.
AB  A + B
2AgO  Ag O2

8. Single Replacement
One element takes the place of another in a compound.
If it is a metal, it will replace the metal, if it is a nonmetal, it will replace the nonmetal
A + BC  AC + B
Fe + CuSO4  FeSO Cu

9. Al Na Cl  + + SR Animation
The single metal trades places with the metal in the compound. Al Na Cl  + +

10. Double Replacement
The positive portions of two ionic compounds are swapped.
AB + CD  AD + BC
Pb(NO3) KI  PbI KNO3

11. Na Cl + K F  + DR Animation
The positive ion of one compound now bonds to the negative ion of the other compound and vice versa Na Cl + K F  +

12. Combustion
A hydrocarbon combines with oxygen to form carbon dioxide and water.
CxHy + O2  CO2 + H2O
2C2H O2  4CO H2O

13. Practice! Composition 2H2 + O2  2H2O _____________
6K + B2O3  3K2O + 2B _____________
HCl + NaOH  NaCl + H2O _____________
4C + S8  4CS2 _____________
CH4 + O2  CO2 + H2O _____________
H2O2  H2 + O2 _____________
3Li + AlCl3  3LiCl + Al _____________
3Rb + P  Rb3P _____________
2NaCl  2Na + Cl2 _____________
4NH3 + 3O2  2N2 + 6H2O _____________ SR DR
Composition
Combustion
Decomposition SR
Composition
Decomposition SR

14. Time for a Lab with Each Reaction!