1. Unit: Chemical Reactions
Day 1 - Notes
Unit: Chemical Reactions
Diatomic elements, Writing formula equations from word equations
Upper left: Thermite reaction, Fe2O3 + Al => 2Fe +2Al2O3 + HEAT!!!
Upper right: potassium in water, K + H2O => KOH + H2 + HEAT
Bottom right: potassium chlorate and sugar, C12H22O11 + 8KClO3 => 12CO2 + 11H2O + 8KCl + HEAT!!!
Bottom left: magnesium reacting with oxygen, Mg + O2 => MgO

2. After today you will be able to…
Name the diatomic elements
Write formula equations given the word equation for a chemical reaction
Balance the chemical equations
Explain law of conservation of mass

3. STANDARD
CLE Explore the mathematics of chemical formulas and equations. Use word problems to translate the names of chemical compounds and elements to chemical equations and balance the equations.

4. ESSENTIAL QUESTION
How do mathematical relationships and experimental data relate to chemical formulas?

5. OBJECTIVE
About 90% students can name the diatomic elements and write formula equations given the word equation for a chemical reaction

6. Complete the practice questions
TASK
Complete the practice questions

7. A chemical equation represents a chemical reaction.
Reactants  Products
“Yield”
Reactants and products are separated from each other with a plus (+) sign.

8. Common forms of chemical reactions…
A + B  C
A  B + C
A + B  C + D

9. Chemical equations can be written as word equations or formula equations. Formula/Skeletal equations can be balanced or unbalanced.

10. Word Equation: Iron + Oxygen  Iron (III) Oxide Formula Equation: 4Fe(s) + 3O2(g) 2Fe2O3(s)
Balanced!

11. Symbols in Chemical Equations
Meaning
(s)
Solid
(l)
Liquid
(g)
Gas
(aq)
Aqueous (dissolved in H2O) 
Reversible reaction
 or 
Heat is added 
Catalyst is added (A substance that speeds up a reaction.)
heat Pt

12. To change word equations into formula equations follow the flow chart…

13. ELEMENT? Monatomic Diatomic
Is the substance an…
ELEMENT?
Monatomic
Diatomic
Just write the symbol
Example:
“Sodium”=Na
Br2 I2 N2 Cl2 H2 O2 F2
Have the subscript “2”
Examples:
“Bromine”=Br2
“Hydrogen” = H2

14. Is the substance a… COMPOUND? CaCl2 N2O4 Ionic Molecular (M +nM)
(nM +nM)
Balance charges!!!
Example: “calcium chloride”
Ca+2 Cl-1
Cl-1
Prefixes for subscripts
Examples:
“dinitrogen tetroxide”
CaCl2
N2O4

15. Law of Conservation of Atoms: There must be the same number of each type of atom before the reaction as after the reaction.

16. Coefficients: Are numbers that go in front of each substance to indicate the number of atoms or molecules that are reacting or being produced.

17. Let’s try some examples! 

18. Helpful tip: Keep all substances and + signs in
Examples: Convert into formula equations…
1. sodium chloride + fluorine  sodium fluoride + chlorine
2. aluminum + sulfur  aluminum sulfide
Helpful tip: Keep all substances and + signs in
line with each other!
Na Cl-1
Na F-1
NaCl + F2 
NaF +
Cl2
Al S-2 Al + S 
Al2S3

19. + Mg3(AsO4)2 ZnS  Zn3(AsO4)2 + MgS
3. zinc magnesium  zinc magnesium
Zn+2 S-2
Mg+2 (AsO4)-3
Zn+2 (AsO4)-3
Mg+2 S-2
sulfide arsenate arsenate sulfide +
Mg3(AsO4)2
ZnS 
Zn3(AsO4)2 +
MgS

20. If the numbers match on either side… You’re balanced!
Examples: Balance the following equation:
___ Al + ___S  ___Al2S3 2 3 2 1 Al 2 3 1 S 3
If the numbers match on either side… You’re balanced!

21. ___ Li + ___O2  ___Li2O Examples: Balance the following equation: 4 21 Li 2 4 2 O 1 2

22. Do not separate polyatomic ions!
Examples: Balance the following equation:
___Fe2(SO4)3 + ___Na3(PO4)  ___Fe(PO4) + ___Na2(SO4) 2 3
Helpful tip:
Do not separate polyatomic ions! 2 2 Fe 1 2 3
(SO4) 1 3 6 3 Na 2 6 1
(PO4) 2 1 2
YES!!!!
Are we balanced?

23. Do now: practice questions
Then: Begin WS 1