1. The Nature of Chemical Reactions

2. Chemical Reaction A well defined example of a chemical change
One or more substances are changed into a new substance
Ex.
Grow
Ripen
Decay
burn

3. Chemical Reaction
You know a chemical reaction has taken place because you will see changes
Ex.
Change in color
Production of gas
Precipitate

4. Chemical Equation
A representation of a chemical reaction that uses symbols to show the relationship between the substances being reacted and the substances being produced

5. Ex. 2Na + Cl2 -------->2NaCl
Reactants
Substances you start with that go into a reaction
Products
The new substance(s) that are formed from the reaction
REACTANTS  PRODUCTS
Ex. 2Na + Cl >2NaCl
Sodium plus Chlorine yields Sodium Chloride

6. THE PRODUCTS AND REACTANTS CONTAIN THE SAME TYPES OF ATOMS… THEY ARE JUST RE-ARRANGED… MASS IS ALWAYS CONSERVED

7. Conservation of mass & energy
In a chemical reaction, matter and energy cannot be created or destroyed… therefore mass and energy are conserved

8. Exothermic reactions
A chemical reaction in which heat is released to the surroundings
Following an exothermic reaction, the temperature of surroundings rises because energy is released

9. Exothermic Reaction

10. Endothermic Reactions
Chemical reaction that requires heat
More energy is needed to break the bonds in the reactants than is given off by forming the product
Following an endothermic reaction the temperature of the surrounding will decrease because energy is needed

11. Endothermic Reaction

12. Energy in Reactions
Activation Energy - The total amount of energy needed for a reaction to take place.
Catalyst / Enzyme – Reduces the total amount of activation energy needed. ** Speeds up the reaction
Inhibitor – Increases the total amount of activation energy needed. ** Slows down the reaction.

13. ACTIVATION ENERGY

14. Activation Energy with a Catalyst

15. Activation Energy with an Inhibitor

16. Reaction Types

17. Synthesis Reactions Synthesis Reactions They have this general form
A reaction where two or more substances combine to form a new compound (combined substances)
They have this general form
A + B  AB
Example
2Na + Cl  2NaCl

18. Synthesis Reaction +

19. Decomposition Reaction
Decomposition Reactions
A reaction in which a single compound breaks down to form two or more simpler substances (breaks substances apart)
They have this general form
AB  A + B
Example
2H2O  2H2 + O2
Electrolysis – when electric current is used to produce this type of reaction

20. Decomposition Reaction

21. Combustion Reaction Combustion Reactions
A reaction that uses oxygen and carbon as reactants and at least one product of the reaction always contains oxygen and/or carbon.
Water and carbon dioxide are common products of these reactions
Example
2CO + O  2CO2

22. Single Displacement Reaction
Single displacement Reactions
A reaction in which one element takes the place of another element in the compound
They have this general form
AX + B  BX + A
Example
3CuCl2 + 2Al  2AlCl3 + 3Cu

23. Single Displacement Reaction

24. Double Displacement Reaction
Double Displacement Reactions
A reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds
They have this general form
AX + BY  AY + BX
Example
Pb(NO3)2 + K2CrO  PbCrO4 + 2KNO3

25. Double Displacement Reaction

26. Type of Reaction Definition
 Equation
Synthesis
Decomposition
Single Replacement
Double Replacement
Two or more elements or compounds combine to make a more complex substance
A + B → AB
AB → A + B
Compounds break down
into simpler substances
Occurs when one element replaces another one in a compound
AB + C → AC + B
Occurs when different atoms in two different compounds trade places
AB + CD → AC + BD
A = Red B = Blue C = Green D = Yellow

27. Balancing Chemical Equations
Purpose: To show the conservation of mass in a chemical reaction
Process: Add COEFFICIENTS to the equation to balance both sides of the equation.

28. Step 1 to Balancing Equations
1. Check the equation for balance by counting the number of atoms of each element on each side of the equation

29. Example of Step 1 Na – 1 Na - 1 Cl – 1 Cl - 2 Be – 1 Be - 1
1. __NaCl + __BeF2 --> __NaF + __BeCl2
Na – 1 Na - 1
Cl – 1 Cl - 2
Be – 1 Be - 1
F – 2 F - 1

30. Step 2 to Balancing Equations
2. Choose coefficients that balance the equation (NEVER change the subscripts)
Coefficients multiply the number of atoms

31. Example of Step 2
1. 2NaCl + __BeF2 --> 2NaF + __BeCl2
Na – Na – 1 2
Cl – 1 2 Cl - 2
Be – 1 Be - 1
F – 2 F – 1 2
** Chlorine and Fluorine are not balanced…until the coefficient is placed.
Placing a coefficient in changes all atoms in that compound.

32. Balancing Equations Tips:
Practice Balancing Equations
It's Elemental - Balancing Act! (practice quiz)

33. Practice Problems
Here are some practice problems. The solutions are in the section below this one.
1. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4
2. __AgNO3 + __LiOH --> __AgOH + __LiNO3
3. __CH4 + __O2 --> __CO2 + __H2O
4. __Mg + __Mn2O3 --> __MgO + __Mn

34. Solutions 1. 2 NaCl + 1 BeF2 --> 2 NaF + 1 BeCl2
2. 2 FeCl3 + 1 Be3(PO4)2 --> 3 BeCl2 + 2 FePO4
3. 1 AgNO3 + 1 LiOH --> 1 AgOH + 1 LiNO3
4. 1 CH4+ 2 O2 --> 1 CO2 + 2 H2O
5. 3 Mg + 1 Mn2O3 --> 3 MgO + 2 Mn