1. Properties of Matter
You have already looked at the difference between physical changes and chemical changes.
Remember:
A chemical change occurs when a substance changes into a new substance with different chemical properties e.g. iron rusting or burning charcoal.

2. Equations
Chemical reactions involve many chemicals, as in explosions of dynamite, bathroom cleaners working on a stain or as in the growth of your body.
Chemists use a word equation to represent these types of reactions…it tells us what reacts and what is produced.

3. The starting materials in a chemical change are called reactants and the new materials made are called products.
Iron oxygen makes rust or iron (III) oxide
Fe O makes Fe2O3
Reactants Products

4. Equation format: Reactants and products can be separated by a (+) sign
Equation format:
Reactants and products can be separated by a (+) sign
All the reactants All the products
Reactant Reactant Product 1 + Product 2
Example:
hydrogen + oxygen water

5. Conserving Mass
The Law of Conservation of Mass states that in a chemical reaction, the total mass of the reactants is always equal to the total mass of the products.
This is because during the chemical reaction the individual atoms that make up the reactants are simply rearranged into new patterns or products, no matter is lost or added during the process.
25 g g ?g
hydrogen + oxygen water

6. methane + oxygen carbon dioxide + water
Skeleton Equations
A skeleton equation is representation of a chemical reaction in which the formulas of the reactants are connected to the formulas of the products by an arrow.
e.g.
methane + oxygen carbon dioxide + water
(word equation)
CH O CO H20
(skeleton equation)

7. Skeleton Equations- Homework
Worksheet
Skeleton Equations- Homework

8. 48g 62g (mass is not the same)
The problem with a skeleton equation is that it does not follow the Law of Conservation of Mass. By looking at the # of atoms on each side of the above equation we can see that they are not the same on both sides of the equation.
CH O CO H20 (skeleton equation)
1 C O 1 C + 2 H
4 H 2O 1 O
16g 32g 44g 18g
48g 62g (mass is not the same)

9. To make the equation follow the Law of Conservation of Mass we must rewrite it as a balanced equation.
To do this we will use multipliers at the front of each chemical formula . These multipliers are called coefficients. These allow us to get the same number of atoms on each side of the equation.
CH O CO H20
1 C O 1 C H
4 H 2O 2 O
16g 64g 44g 36g
80g = 80g (mass is now the same)

10. Balancing Equations Activity

11. Wednesday, March 10, 2010

12. Settle down
Read between the lines
Merry go round
Strawberry shortcake
Square dance

13. Homework Check/Review
2 questions from balancing equations

14. Finish balancing equations sheet from yesterday

15. How to balance an Equation
1)      write the word equation for the reaction
2)     Write the skeleton equation by replacing each name with the correct formula
Lead (II) Nitrate + Potassium Iodide Lead(II) Iodide Potassium Nitrate
Pb(NO3) KI PbI KNO3

16. 3)     Count the # of atoms of each type in the reactants and products
Pb(NO3) KI PbI KNO3
Pb: 1
N: 2
K: 1
I: 1
O: 6
*** Use the ECHO rule : Count and balance the atoms in this order Element (all) then Carbon Hydrogen and finally Oxygen
Pb: 1
N: 1
K: 1
I: 2
O: 3

17. 2 2 Pb: 1 N: 2 K: 1 I: 1 O: 6 Pb: 1 N: 1 K: 1 I: 2 O: 3 2 2 2 2 6
4)    multiply each of the formulas by the appropriate coefficients to balance the number of atoms
Pb(NO3) KI PbI KNO3 2 2
Pb: 1
N: 2
K: 1
I: 1
O: 6
Pb: 1
N: 1
K: 1
I: 2
O: 3 2 2 2 2 6
We now have the same number of each element on both sides so the equation is balanced.

18. Worksheet
Balancing Equations

19. Balancing Equations Worksheet
Homework Check
Balancing Equations Worksheet

20. Beginning of the end
Better safe than sorry
No where in sight
All hands on deck
Growing old

21. Finish Balancing Equations Sheet (from yesterday)
Worksheet
Finish Balancing Equations Sheet (from yesterday)

22. New Balancing Equations Sheet
Worksheet
New Balancing Equations Sheet

23.                                                
Waterfall
Partly cloudy
Vitamin A deficiency
No two ways about it
Pour down
Open & closed case

24. Balancing Equations- Review
Balance each of the following equations:
Al + O2  Al2O3
NaOH + HBr  NaBr + H2O
Mg + N2  Mg3N2
Co + Cl2  CoCl
Ca + OH  Ca(OH)2