Today’s Catalyst 9/6/2012
Classify the following as either chemical or
physical properties of matter:
1. reactivity chemical
2. pH chemical
3. solubility Physical
4. heat of combustion
Physical
5. color
6. texture Physical
7. density Physical
chemical
Today’s Catalyst 9/6/2012
Classify the following as either physical or chemical changes:
8. Potatoes rot
9. A nail rusts
Chemical
Chemical
10. A piece of sulfur is burned
11. Ice Melts
Chemical
Physical
12. Tearing tin foil
13. Melting an iron bar
Physical
Physical
Unit 2 Exam Reflection
What was YOUR overall score on the
quiz?
What was your best topic? What was your
worst topic?
How much time did you spend preparing
for the quiz? What did you do to prepare?
Do you feel your score is connected to
your preparation?
What is one thing YOU can do to achieve
your quiz/class goal?
What is one thing Mrs. Lewis can do to
help you achieve your goal?
Modern Atomic
Theory
{ 4 Dead Guys
The Competition to End
All Competitions
Your job, guess how many times I can cut
the paper in half!!

Cut your sheet of paper in half.
Continue this procedure with
one of the halves until you can
no longer continue to cut the
piece of paper. Keep a tally of
the number of cuts I make.
Call yourself Democritus…
Democritus suggested that if
you kept splitting an object in
half, you would eventually get
to a tiny, fundamental piece that
can’t be broken down any
further.
By the end of class today I
will be able to…
Understand Dalton’s 5 postulates.
• State which of Dalton’s postulates
have remained unchanged and
which postulates have been
modified to create the Modern
Atomic Theory.
•
Atom
The smallest particle of
an element that has the
chemical properties of
that element
Key Players in Modern
Atomic Theory
John Dalton
•
•
English school
teacher turned
Chemist
Proposed his atomic
theory in 1808
All matter is
composed of tiny
particles called
atoms
Postulate 1
Atoms of a given
element are identical
Postulate 2
Atoms of a given
element are
different from those
of any other element
Postulate 3
Atoms of different
elements combine in
simple whole-number
ratios to form chemical
compounds
Postulate 4
Examples:
CO2
Cu(NO3)2
Hold up a card to
indicate how many
atoms of the element
in RED exist in the
compound

H2O
H2O
2 Hydrogen
1 Oxygen
Na2SO4
Na2SO4
2 Sodium
1 Sulfur
4 Oxygen
Fe(NO3)2
Fe(NO3)2
1 Iron
2 Nitrogen
6 Oxygen
(NH4)3PO4
(NH4)3PO4
3 Nitrogen
12 Hydrogen
1 Phosphorus
4 Oxygen
Let’s Finish That Last
Postulate….
• Take out your notes
Atoms cannot be created
or destroyed. In
chemical reactions,
atoms are combined,
separated, or rearranged
Postulate 5
WHATEVER you START with in a
chemical reaction or equation…you
MUST also END with…
 This is the LAW of Conservation of
Matter (or Mass)


Specifically it states Matter CANNOT
be created OR destroyed in a chemical
reaction…
What this means…
Where Dalton was Wrong!
***All atoms of a given
element are NOT identical
Postulate should read: all
atoms of a given element
have the same # of protons
Group Practice
I will display a slide. Hold up
the card (1-5) of the postulate
that is described by the
statement or scenario
All matter is
composed of
extremely small
particles called atoms
(Postulate 1)
Atoms of different
elements combine in
simple whole-number
ratios to form chemical
compounds
(Postulate 4)
#3:
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3 (aq)
Atoms cannot be created or
destroyed. In chemical reactions,
atoms are combined, separated,
or rearranged.
(Postulate 5)
Independent Practice
(homework if not finished
in class)