 Write chemical equations to describe chemical reactions
 Balance chemical equations
 Classify and identify chemical reactions
 Predict products from chemical reactions

 YouTube - ammonium dichromate volcano
 YouTube - Nitrogen Triiodide Detonation
 YouTube - Sodium and Water
 YouTube - Reaction of Sodium & Chlorine (with subtitles)

 Evidence of a chemical reaction
 Temperature change
 Change in color

 Evidence of chemical change
 Gas production (bubbles, fizzing)
 Appearance of a solid (precipitate)

 Representing chemical reactions:
 Reactants: starting substances (written on the left side)
 Products: substances that result from the reaction
(written on the right side)

 Symbols used in chemical equations
Symbol Meaning
 Yield (placed between reactants and products)
+
(s)
Separate two or more reactants or products
Substance is in a solid state
(l)
(g)
(aq)

Pt
Substance is in a liquid state
Substance is in a gaseous state
Substance is in an aqueous (water) solution
Heat is applied
A substance written above an arrow indicates it is a catalyst needed for the reaction

 Word equations: indicates the reactants and products in a chemical reaction iron(s) + chlorine (g)
 iron (III) chloride (s)
“iron and chlorine react to produce iron(III) chloride”
 Word equations lack important information
 Skeleton equations
 Uses chemical formulas to represent reactants and products
Fe (s) + Cl
2
(g)

FeCl
3
(s)


1.
Write the skeleton equations for the following:
Hydrogen (g) + Bromine (l)
 hydrogen bromide (g)
2.
Carbon monoxide (g) + oxygen (g)
 carbon dioxide (g)


1.
Write the skeleton equations for the following:
H
2
Hydrogen (g) + Bromine (l)
 hydrogen bromide (g)
(g) + Br
2
(l)

HBr (g)
2.
Carbon monoxide (g) + oxygen (g)
 carbon dioxide (g)
CO (g) + O
2
(g)

CO
2
(g)

 Chemical equations:
 Must obey “law of conservation of matter”
 Must show that the number of atoms of each substance is the same before and after the reaction.
 A chemical equation has to be BALANCED
 To balance chemical equations, COEFFICIENTS (whole number)are written in front of a reactant or product.
 If coefficient is 1, it is not written

 Steps for balancing equations
1.
Write the skeleton equation for the reaction. Ex.
Hydrogen gas reacts with chlorine gas and yields gaseous hydrogen chloride.
H
2
(g) + Cl
2
(g)

HCl(g)
2.
Count the atoms of each substance for the reactants and products.
REACTANTS
H :
Cl :
PRODUCTS
H :
Cl :

3.
Place coefficients (ONLY IN FRONT OF A
REACTANT OR PRODUCT) to make number of atoms of each element equal on both sides of the equation. (#atoms= coefficient x subscript)
H
2
(g) + Cl
2
(g)

HCl(g)
REACTANTS
H :
Cl :
PRODUCTS
H :
Cl :

4.
Write coefficients in lowest ratio possible
H
2
(g) + Cl
2
(g)

HCl(g)
5.
Check your answer.
REACTANTS
H :
Cl :
PRODUCTS
H :
Cl :

1. Write a balanced chemical equation if magnesium bromide reacts with chlorine and yield magnesium chloride and bromine.

2.
Write a balanced chemical equation for:
Potassium nitrate
 potassium nitrite + oxygen

3.
Balance the following reaction
CaO + H
2
O

Ca(OH)
2

4.
Reactions for gummy bear sacrifice
KClO
3

KCl + O
2
C
12
H
22
O
11
+ O
2

C + CO
2
+ H
2
O