1. Objectives
To learn the signals or evidences that show a chemical reaction may have occurred

3. Whoosh
Can You Identify any Evidences of a Chemical Reaction?

4. To learn to identify the characteristics of a chemical reaction
Objectives
To learn to identify the characteristics of a chemical reaction
To learn the information given by a chemical equation

5. Physical states of compounds are often given in a chemical equation.

6. Chemical reactions involve a rearrangement of the ways atoms are grouped together.
A chemical equation represents a chemical reaction.
Reactants are shown to the left of an arrow.
Products are shown to the right of the arrow.

7. The Law of Conservation of Mass
The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical reaction.
Plop, Plop, Fizz, Fizz…..
A chemical reaction involves the rearrangement of atoms to form new substances. (Coins)

8. In a chemical reaction atoms are not created or destroyed.
All atoms present in the reactants must be accounted for in the products. (Video Clip) (Magnets)
Same number of each type atom on both sides of arrow
___CH4 ___O ___CO ___H2O

9. In a chemical reaction atoms are not created or destroyed.
All atoms present in the reactants must be accounted for in the products. (Video Clip) (Magnets)
Same number of each type atom on both sides of arrow
___CH4 ___O ___CO ___H2O

10. To learn to identify the characteristics of a chemical reaction
Objectives Review
To learn the signals or evidences that show a chemical reaction may have occurred
To learn to identify the characteristics of a chemical reaction
To learn the information given by a chemical equation
Work Session: page 234 1, 5, 6, 7, 8
Video of Various Chemical Rx’s Ch 7(Silver I)

11. To learn to write a balanced equation for a chemical reaction
Objectives
To learn to write a balanced equation for a chemical reaction
Are you ready??

13. C2H5OH + 3O2  2CO2 + 3H2O A representation of a chemical reaction:
reactants products
Reactants are only placed on the left side of the arrow, products are only placed on the right side of the arrow.
The equation is balanced because all atoms present in the reactants are accounted for in the products.
The balanced equation represents an overall ratio of reactants and products, not what actually “happens” during a reaction.

14. Atoms (mass) are always conserved Can only change the coefficients
A chemical reaction is balanced by using a systematic approach:
Atoms (mass) are always conserved
Can only change the coefficients
Balance by trial and error starting with the most complicated molecule(s)
At the end check to be sure the equation is balanced (same numbers of all types of atoms on the reactant and product sides)

15. Example: 
Hydrogen gas and oxygen gas combine to form liquid water.
Write the formulas of the reactants and products to give the unbalanced chemical equation. ___H2(g) + ___O2(g)  ___H2O(l)

16. Use a pencil and don’t be afraid of erasing!
A chemical reaction is balanced by using a systematic approach: (Patch’s Interpretation)
Make Sure you have the equation written correctly and leave spaces in front of each compound formula.
Use a pencil and don’t be afraid of erasing!
Make sure you are NOT violating the Law of Conservation of Mass!!

17. ___K + ___H2O  ___H2 + ___KOH ___CH4 + ___O2  ___ CO2 + ___H2O
More Examples:
___N2 + ___H2  ___ NH3
___O2  ___ O3
___K + ___H2O  ___H2 + ___KOH
___CH4 + ___O2  ___ CO2 + ___H2O
___C2H5OH + ___O2  ___ CO2 + ___H2O
___C3H8 + ___O2  ___ CO2 + ___H2O
___HF + ___SiO2  ___ SiF4 + ___H2O
___NH3 + ___O2  ___ NO + ___H2O

18. ___HNO3  ___NO2 + ___ H2O + ___O2
Independent practice:
___NH4NO2  ___N2 + ___H2O
___NO  ___ N2O + ___NO2
___HNO3  ___NO2 + ___ H2O + ___O2

19. I. The number of molecules is conserved.
Concept Check
Which of the following are true concerning balanced chemical equations? There may be more than one true statement.
I. The number of molecules is conserved.
II. The coefficients tell you how much of each substance you have.
III. Atoms are neither created nor destroyed.
IV. The coefficients indicate the mass ratios of the substances used.
V. The sum of the coefficients on the reactant side equals the sum of the coefficients on the product side.
Only III is correct.

20. Let’s use all of your skills to write a reaction equation to describe the following:
Solid Carbon reacts with gaseous oxygen to form gaseous carbon dioxide.
Solid Mercury (II) oxide decomposes to produce elemental mercury metal and gaseous oxygen.
Solid zinc is added to an aqueous solution of hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water.

21. To learn to write a balanced equation for a chemical reaction
Objectives Review
To learn to write a balanced equation for a chemical reaction
Work Session:
page 234: 31, 32, 33, 34, 35, 36
Page 237: 1-8

22. This is the end of the required material for this chapter.

23. Example: 
Hydrogen gas and oxygen gas combine to form liquid water.
Balance by trial and error starting with the most complicated molecule(s).

24. Example: 
Hydrogen gas and oxygen gas combine to form liquid water.
At the end check to be sure the equation is balanced (same numbers of all types of atoms on the reactant and product sides). 2H2(g) + O2(g)  2H2O(l)

25. Balancing a Chemical Equation
Unbalanced equation
Balancing the equation
The balanced equation CH O2  CO H2O