1. Chemical formulae and chemical equations

2. Review of Prior knowledge
Can you write the chemical formula of the following substances?
Magnesium chloride
Carbon dioxide
Methane
Aluminium Sulfate

3. Welcome to the 101th CVSS chemistry awards.
To find out if you have been nominated for most outstanding chemistry award please check under your desk.

4. Objectives for the day…
Construct chemical equations, with state symbols, including ionic equations.
Interpret chemical equations with state symbols.
Construct ionic chemical equations.

5. sodium + chlorine  sodium chloride
Objective 1: Constructing chemical equations, with state symbols, including ionic equations
An equation can be written in words – a word equation.
sodium + chlorine  sodium chloride
An equation can also be written with symbols and formulae instead of words – a chemical equation.
2Na + Cl2  2NaCl

6. In a Chemical Reaction:
A process in which at least one new substance is produced as a result of chemical change
Reactants used.
Products formed.
Reactants
Products
Qs that can be asked:
A. How does an equation indicate a change in
the identity of the reacting substances?
The formulas of the reactants are different than the formulas of the products.
B. How did the pink and blue reactants
combine?
1 pink combined with 1 blue
C. Did all the reactants form product? Why or
why not?
No. There were more pink than blue.

7. Analogy Ingredients: 12 oz of dough 4 oz mushroom 12 slices pepperoni
8 oz cheese
5 oz tomato sauce
These ingredients are used to make a pizza.
How would you write the recipe in word equation for putting together a pizza?
12 oz dough + 4 oz mushroom + 12 slices pepperoni + 8 oz cheese + 5 oz tomato sauce  1 pizza

8. Constructing Chemical Equations
What Chemical Equations Show
The reactants used.
The products formed.
The states of the reactants and products.
The arrow means ‘react to form’ and reaction proceeds from left to right).
Reactants
Products
Eg:
2Mg (s) + O2(g) MgO (s)
State symbols

9. Constructing Chemical Equations
The Reaction Between Hydrogen and Oxygen
Word equation:
Chemical equation:
hydrogen + oxygen water
State symbol
2H2(g) + O2(g) H2O(l)
Ask student to state the formula of the compound for the chemical equation.

10. Constructing Chemical Equations
Balancing Equations
All chemical equations (with state symbols) must be balanced.
A balanced equation:
shows the formulae of all the reactants and all the products in a reaction.
has the same number of atoms of each element on both sides of the equation.

11. Law of Conservation

12. Balancing equation Step 1
Write down the formula of the reactant and products. 2
Check the number of atoms of each element on both sides of the equation. If the equation is not balanced, proceed to step 3. 3
Balance the equation by placing numbers in front of the formulae of the substances in the equation. The number ‘1’ is not written. 4
Includes the state symbols in the equation.

13. Methane + oxygen  carbon dioxide + water
Balancing equation
Step 1
Write down the formula of the reactant and products.
Methane + oxygen  carbon dioxide + water
CH4 + O2  CO2 + H2O 13

14. Not Balanced Balancing equation Step 2
Check the number of atoms of each element on both sides of the equation.
If the equation is not balanced, proceed to step 3.
CH4 + O2  CO2 + H2O
C atom = 1
H atoms = 4
O atoms = 2
C atom = 1
H atoms = 2
O atoms = = 3
Not Balanced 14

15. Balanced Balancing equation Step 3
Balance the equation by placing numbers in front of the formulae of the substances in the equation. The number ‘1’ is not written.
CH4 + O2  CO2 + H2O 2 2
C atom = 1
H atoms = 4
O atoms = 4
C atom = 1
H atoms = 4
O atoms = 4
Balanced 15

16. CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (g)
Balancing equation
Step 4
Includes the state symbols in the equation.
CH4 (g) + 2O2 (g)  CO2 (g) + 2H2O (g) 16

17. Learning Check for Balancing Equation
Step 1
Write down the formula of the reactant and products.
aluminium + chlorine gas  aluminium chloride
Al + Cl2  AlCl3 17

18. Not Balanced Balancing equation Step 2
Check the number of atoms of each element on both sides of the equation.
If the equation is not balanced, proceed to step 3.
Al + Cl2  AlCl3
Al atom = 1
Cl atoms = 2
Al atom = 1
Cl atoms = 3
Not Balanced 18

19. Balanced Balancing equation Step 3
Balance the equation by placing numbers in front of the formulae of the substances in the equation. The number ‘1’ is not written.
Al + Cl2  AlCl3 2 3 2
Al atom = 2
Cl atoms = 6
Al atom = 2
Cl atoms = 6
Balanced

20. Balancing equation Step 4 Includes the state symbols in the equation.
2Al (s) + 3Cl2 (g)  2AlCl3 (s)

21. Learning check for Balancing equation
Write the balanced chemical equation with state symbol. Iron + oxygen gas  Iron(III) oxide 4Fe (s) + 3O2 (g)  2Fe2O3 (s) Sodium + bromine  sodium bromide 2Na (s) + Br2 (l)  2NaBr (s)
Ask someone to do on the big whiteboard

22. Learning Objective 2: Interpret chemical equations with state symbols
2Na + Cl2  2NaCl
Two atoms of Na react with one molecule of Cl2to produce 2 unit of NaCl.

23. What did we learn this lesson…
What is a word equation.
What is a chemical equation.
What is a reaction (reactants and products).
What is law of conservation.
How to write a balanced equation with state symbols.
How to deduce a chemical equation.