Do Now:
Explain this joke.
The last 2 weeks we have…
investigated how evidence of chemical
reactions indicates that new substances with
different properties are formed.
Evidence of a chemical reaction:
(chemical change)
•
•
•
•
Production of a gas (bubbling, fizzing or foaming)
A change in temperature or light (an energy change)
Appearance of a precipitate (solid material)
A change in color
Chemical Reaction Dehydration of sugar…
Reactants
Physical
properties
White crystal
Chemical
equation
C12H22O11
products
To
yield
Black crystal/powder and white gas

12 C + 11 H2O (vapor)

Visual
model
+
Number
of atoms

12 carbons 22 Hydrogen 11 oxygen
12 carbons 22 hydrogens 11 oxygens
Let’s make some visual models with
SKITTLES
You will be able to…
8.5(D) recognize that chemical formulas are used to identify substances and determine the number
of atoms of each element in chemical formulas containing subscripts;
8.5(F) recognize whether a chemical equation containing coefficients is balanced or not and how
that relates to the law of conservation of mass.
Key
Red-Chlorine
Orange-Sodium
Yellow-Oxygen
Green-Hydrogen
Purple- Carbon
Review: How to make a molecule…
Formula
H2O
Subscript
No Subscript,
There is only 1
atom of oxygen in
the molecule
Visual model
Review: How to make a molecule…
Formula
H2O
Subscript
No Subscript,
There is only 1
atom of oxygen in
the molecule
H2O2
Visual model
Review: How to make a molecule…
Formula
6 H2O
Coefficient- How many
molecules you have.
Visual model
H2O
1 molecule of H2O
3 H2 O
3 molecules of H2O
Let’s now model another chemical equation
with our SKITTLES…
Reactants
Chemical
equation
products

C + O2
CO2

Visual
model
+
Word
equation
1 atom carbon reacts with
1 molecule of oxygen
Number
of atoms
1 carbon
2 oxygen
To
yield

1 molecule of CO2
1 carbon
2 oxygen
Is it a balanced equation? How do we know?
Reactants
Chemical
equation
products

C + O2
CO2

Visual
model
+
Word
equation
Number
of atoms

1 atom carbon + 1 molecule oxygen
1 carbon
2 oxygen
1 molecule CO2
1 carbon
2 oxygen
Law of Conservation of Mass
Matter is not created or destroyed, it just
changes forms.
In a chemical reaction…
More practice…
Reactants
Chemical
equation
products

2C + 2O2
3CO2

Visual
model
+
Word
equation
Number
of atoms
To
2 atoms carbon react with 2 molecule yield
oxygen
2 carbons
4 oxygen
3 molecules CO2
3 carbons
6 oxygens
Is it balanced?
The model above is best represented by:
a. H2O
b. 2OH
c. HOOH
d. H2O2
The above model shows:
a. 10 atoms
b. 2 molecules
c. 2CH3Cl
d. All of the above
6CO2+ 6H20+ Sun’s light C6H12O6+6O2
The above reaction…
a. is photosynthesis
b. Is respiration
c. Transforms radiant energy into chemical
energy
d. Both a and c.
Organic Molecules all contain…
a.
b.
c.
d.
Sulfur
Carbon
Oxygen
nitrogen
All of the following are organic molecules
except…
a.
b.
c.
d.
C6H12O6
CH4
C6H6O
H20