1. Divide your notebook page into 4 sections:
Synthesis
Decomposition
Single Replacement (displacement)
Double Replacement (displacement)

2. Chemical Reactions and the Law of Conservation of Mass

3. Chemical Reactions Substances change to produce different substances
During a reaction, bonds are broken, atoms are rearranged, and new bonds are formed.
New substances have different chemical and physical properties.

4. Signs of a Chemical Reaction
Color change,
Formation of a gas or a solid
Production of energy.

5. Chemical Formulas
A chemical formula uses symbols and subscripts to describe the makeup of a compound.
Chemical formulas can often be written from the names of covalent and ionic compounds.
Chemical symbol of oxygen
H2O
Chemical symbol of hydrogen
Subscript showing number of hydrogens

6. Self-Check
The chemical formula for water is always H2O. What is the ratio of hydrogen to oxygen atoms in a molecule of water?
A. 1:1
B. 1:2
C. 2:1
D. 2:2

7. Answer
The chemical formula for water is always H2O. What is the ratio of hydrogen to oxygen atoms in a molecule of water?
A. 1:1
B. 1:2
C. 2:1
D. 2:2

8. Self-Check
One molecule of glucose has the formula C6H12O6. How many atoms make up a glucose molecule?
A. 3
B. 6
C. 12
D. 24

9. Answer
One molecule of glucose has the formula C6H12O6. How many atoms make up a glucose molecule?
A. 3
B. 6
C. 12
D. 24 ( )

10. Chemical Equation
A chemical equation uses chemical formulas, chemical symbols, and coefficients to describe a reaction.

11. Balancing Equations
Balancing an equation requires that the same numbers and kinds of atoms be on each side of the equation.
A balanced equation illustrates the Law of Conservation of Mass: mass is neither created nor destroyed during ordinary physical and chemical changes.

12. To Balance Chemical Equations!!
Let’s Learn How…
To Balance Chemical Equations!!

13. _____ H2 + _____ Cl2 --> _____ HCl
This is a chemical equation
The + sign shows the two chemicals react with each other
Those chemicals are the REACTANTS
The arrow shows the direction of the reaction
The chemical formula to the right of the arrow is the PRODUCT

14. _____ H2 + _____ Cl2 --> _____ HCl
The Law of Conservation of Mass states that the mass of the products must equal the mass of the reactants
So…
If you have an element on one side of the arrow, you will have it on the other
The number of atoms of an element on the left will be the same number on the right

15. _____ H2 + _____ Cl2 --> _____ HCl1 1 2

16. Self-Check What does the law of conservation of matter state?
A. The total mass of the reactants is greater than the total mass of the products
B. The total mass of the products is greater than the total mass of the reactants
C. The total mass of the reactants equals the total mass of the products

17. Answer What does the law of conservation of matter state?
A. The total mass of the reactants is greater than the total mass of the products
B. The total mass of the products is greater than the total mass of the reactants
C. The total mass of the reactants equals the total mass of the products

18. Self Check
A magnesium ribbon is burned in a closed flask. How does the total mass compare before & after the reaction?
A. The total mass is less after the reaction
B. The total mass is more after the reaction
C. The mass of the magnesium ribbon is the same due to the Law of Conservation of Mass
D. The total mass is the same after the reaction

19. Answer
A magnesium ribbon is burned in a closed flask. How does the total mass compare before & after the reaction?
A. The total mass is less after the reaction
B. The total mass is more after the reaction
C. The mass of the magnesium ribbon is the same due to the Law of Conservation of Mass
D. The total mass is the same after the reaction

20. Self-Check Balance the following equation:
____ HgO  ____ Hg + ____ 02
A. 1 HgO  1 Hg
B. 2 HgO  2 Hg
C. 1 HgO  2 Hg
D. 2 HgO  2 Hg

21. Answer Balance the following equation: ____ HgO  ____ Hg + ____ 02
A. 1 HgO  1 Hg
B. 2 HgO  2 Hg
C. 1 HgO  2 Hg
D. 2 HgO  2 Hg

22. Types of Reactions: Synthesis
A synthesis reaction is a reaction in which two or more substances combine to form a compound.
Example:
H2 + Cl2  2 HCl

23. Types of Reactions: Decomposition
A decomposition reaction is a reaction in which a compound breaks down to form two or more simpler substances.
Example:
2 H2O  H2 + O2

24. Types of Reactions: Single Displacement
A single-displacement reaction is a reaction in which an element takes the place of another element that is part of a compound.
Example
Cl2 + 2NaBr → 2NaCl + Br2

25. Type of Reactions: Double Displacement
A double-displacement reaction is a reaction in which ions in two compounds exchange places.
Example
CH4 + 2 O2  CO2 + 2 H20

26. Types of Reactions - Summary

27. Energy & Reactions Energy is given off in exothermic reactions.
Energy is used in an endothermic reaction.
The law of conservation of energy states that energy is neither created nor destroyed.
Activation energy is the energy needed for a reaction to occur.
The rate of a chemical reaction is affected by temperature, concentration, surface area, and the presence of an inhibitor or catalyst.