1. CHEMICAL REACTIONS
Chapter 8

2. Chemical equations have ingredients also, we just call them REACTANTS
Chemical equations have products also, we call them PRODUCTS
Chemical equations tell us how to get from reactants to products--just like a recipe

3. The arrow in the middle tells us how to get from one side to the other side. Since no information is given, we can assume that this reaction will go from the reactants to the products as soon as the reactants are mixed together (no baking required)

4. Additional Signs…

6. Chemical reactions occur when substances undergo chemical changes to form new substances.
Chemical reactions rearrange atoms –Law of Conservation of Mass

7. Energy Energy is conserved in chemical reactions.
Chemical energy is the energy released when a chemical compound reacts to produce new compounds.
The total energy that exists before the reaction is equal to the total energy of the products and their surroundings.
An exothermic reaction is a chemical reaction in which heat is released to the surroundings.
An endothermic reaction is a chemical reaction that absorbs heat.

8. Is This an Exothermic or Endothermic Reaction?
Paper burning with bright flame
Plastics becoming brittle after being left in the sun
Firecracker exploding

9. Chemical Reactions Evidence of a Chemical Reaction
Rearrangement of atoms in molecules
Evidence
Color Changes
Formation of a Solid
Formation of a Gas
Heat Change
Absorption
Emission
Light emission
Sound emission

10. Evidence of a Chemical Reaction Color Change

11. Evidence of a Chemical Reaction Formation of a Solid

12. Evidence of a Chemical Reaction Formation of a Solid

13. Evidence of a Chemical Reaction Formation of a Gas

14. Evidence of a Chemical Reaction Emission of Light

15. Evidence of a Chemical Reaction Emission or Absorption of Heat

16. Review What is a substance that undergoes a chemical change?
What is the substance produced by a chemical change called?
What happens to the atoms of a substance that undergoes a chemical reaction?
What are the two kinds of chemical reactions with respect to energy?
What are evidences of chemical reaction?

17. Types of Reactions

18. Types of Reactions
A synthesis reaction is a reaction in which two or more substances combine to form a new compound.
Synthesis reactions have the following general form: A + B → AB
Example: In the following synthesis reaction, the metal sodium reacts with chlorine gas to form sodium chloride, or table salt.
2Na + Cl2 → 2NaCl

19. Types of Reactions
A decomposition reaction is a reaction in a single compound breaks down to form two or more simpler substances.
Decomposition reactions have the following general form: AB → A + B
Example: The following shows the decomposition of water.
2H2O → 2H2 + O2
Electrolysis is the process in which an electric current is used to produce a chemical reaction, such as the decomposition of water.

20. Types of Reactions
A single-displacement reaction is a reaction in which one element or radical takes the place of another element or radical in the compound.
Single-displacement reactions have the following general form: AX + B → BX + A
Example: The single-displacement reaction between copper(II) chloride and aluminum is shown as follows.
3CuCl2 + 2Al → 2AlCl3 + 3Cu

21. Pb(NO3)2 + K2CrO4 → PbCrO4 + 2KNO3
Types of Reactions
A double-displacement reaction is 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.
Double-displacement reactions have the following general form: AX + BY → AY + BX
Example: The double-displacement reaction that forms lead chromate is as follows.
Pb(NO3)2 + K2CrO4 → PbCrO4 + 2KNO3

22. Double Displacement Reactions Precipitation Reactions
Potassium iodide mixed with Lead(II) nitrate
Bright yellow precipitate
Write the balanced reaction.
2KI + Pb(NO3)2 ⟶ 2KNO3 + PbI2
How do you know which product is the solid?

23. Types of Reactions
A combustion reaction is the oxidation reaction of an organic compound (a hydrocarbon), in which heat is released.
Combustion reactions use oxygen as a reactant.
Water is a common product of combustion reactions.
In combustion the products depend on the amount of oxygen available for the reaction
Combustion of a hydrocarbon…
CH4 + O2 ⟶ CO2 + H2O
CH4 + O2 ⟶ CO + H2O

24. Remember the patterns…

25. Types of Reactions

26. Identifying Reactions & Predicting Products…

27. Identifying Reactions & Predicting Products…

28. Identifying Reactions & Predicting Products…