Unit 2 – Section A
Why we Use What We Do
HW 1
Read & take notes on sections A.1
(pg . 110) & A.2 (pg. 111) , being
certain to address all the examples in
section A.2
A.1 – Properties Make the Difference
Physical properties:
» Color
» Density
» Odor
May be determined without altering chemical
make-up
Ex.
8.96 g/cm3
2.06 g/cm3
A.1 – Properties Make the Difference
(continued)
Physical change:
» Melting
» Boiling
» Bending
An actual physical change, material unaltered
Ex.
A.1 – Properties Make the Difference
(continued)
Chemical change is when a material changes
into one or more new substances.
A.1 – Properties Make the Difference
(continued)
Chemical properties determine a chemical’s
usefulness.
A.2 – Physical & Chemical Properties
S.P. 1: Copper compounds
are often blue in color
PHYSICAL PROPERTY
S.P. 2: Oxygen gas supports
the burning of wood
CHEMICAL PROPERTY
A.2 – Physical & Chemical Properties
(continued)
1: Pure metals have a
high luster (shiny)
PHYSICAL PROPERTY
2: The surface of some
metals become dull
when exposed to air
CHEMICAL PROPERTY
A.2 – Physical & Chemical Properties
(continued)
3. N2 which is a relatively
nonreactive element at
room temp. , can form NO2
at high temperatures of an
auto engine.
CHEMICAL PROPERTY
4. Milk turns sour if
left too long at room
temperature
CHEMICAL PROPERTY
A.2 – Physical & Chemical Properties
(continued)
5. Diamonds are hard
enough to be used as
coating for drill bits.
PHYSICAL PROPERTY
6. Metals are
typically ductile (can
be drawn into wires)
PHYSICAL PROPERTY
A.2 – Physical & Chemical Properties
(continued)
7. Leavened bread dough
increases in volume if it
is allowed to rise before
baking.
CHEMICAL PROPERTY
8. Unreactive argon
gas, rather than air,
is used to fill many
light bulbs to prevent
the metal filament
wire inside the bulb
from being destroyed
through oxidation.
CHEMICAL PROPERTY
A.2 – Physical & Chemical Properties
(continued)
9. Generally, metals
are better conductors
of heat and
electricity than are
nonmetals.
CHEMICAL PROPERTY
HW 2
Read & take notes on sections A.3 & A.4.
And complete the following
Element Cards
A.3 – Properties Matter: Designing the new coin…
Every element has its own physical & chemical
properties.
When deciding what to use how do we decide
the best substance for our needs?
1.
2.
3.
4.
5.
6.
7.
8.
9.
A.4 – The Chemical Elements
How are chemical elements placed on the
periodic chart of elements?
A.4 – The Chemical Elements
(continued)
Two major classes of elements are metals
and nonmetals. Several elements have
properties of both and are called metalloids.
HW 3
Pre-read section A.5
A.5 – Metal or Nonmetal?
See pgs 115 – 117
By the end of class – answer how you did on the
predictions AND questions 1-4 on pg 117.
A.5 – Metal or Nonmetal? (Lab follow up)
Common lab issues:
1) Make certain you answer the question being
asked.
2) Restate the question in the form of a
statement and ADD your information.
3) Make it a goal to show me that you have
actually thought about the question, rather
than prove you never even considered it.
(example next slide)
No shoveling please . . .
Q – How did you do on your predictions? (tell
me below)
Student answer:
“On my predictions I made the common sense
answer but there was a few more per question
and a few surprising ones but relatively well.”
As apposed to the following
Q – How did you do on your predictions? (tell
me below)
Student answer:
“Malleable * I got 2/4 correct. Me – Mg & Zn,
results Al, Cu , Mg ,Zn
HW 4
Pre-read and take notes on A.6
And make certain you have your element
cards with you when you come to class
next day.
A.6 – The Periodic Table
(A Brief History)
By mid-1800s, chemists identified ~60
elements. Five were nonmetals, gasses at room
temperature.
hydrogen (H)
oxygen (O)
nitrogen (N)
fluorine (F)
chlorine (Cl)
Two liquids were also known.
Metal : mercury (Hg)
Nonmetal : bromine (Br)
Scientist tried to place elements near one
another based on similar properties.
A.6 – The Periodic Table
(A Brief History)
Dimitri Mendeleev, a Russian chemist
published one of the first such tables in
1869.
A.6 – The Periodic Table
(continued)
An offshoot is still used today based on two
characteristics:
1) atomic masses and
2) combining capacity.
A.7 – Grouping the Elements
See page 119
HW 5
Read & take notes on sections A.8
A.8 – The Pattern of Atomic Elements
Refresher : Atoms consist of sub-atomic particles
Protons , small positively charged
particles and neutrons, particles
with no charge make up the
nucleus of an atom.
Electrons are a negatively charges
particles found in varying energy
levels surrounding the nucleus.
A.8 – The Pattern of Atomic Elements
(continued)
The number of protons in an atom
is called the atomic number. For
the example to the right the value
would be _____
Mass number is the total number
of protons and neutrons in the
nucleus of an atom. Example to the
right the value would be ____
A.8 – The Pattern of Atomic Elements
(continued)
While all atoms of particular
elements have the same number of
protons, they contain different
number of neutrons.
Example (from book) , carbon (C)
always has 6 protons, but may
contain 6,7, or 8 neutrons – these
are called isotopes.
A.8 – The Pattern of Atomic Elements
(continued)
So why are the atomic masses we
see on the periodic table not
integers (whole numbers)?
They take into account the
weighted average of the atomic
masses of the naturally occurring
isotopes.
Candium
Isotopes
HW 6
Pre-read section A.9
A.9 – Periodic Variation in Properties
See pgs 122-123 Graphing lab we’ll do together.
After graphing the data , please answer
questions 1,3 & 4 on pg 123
HW 7
Read & take notes on sections A.10 and
answer A.11
A.10 – Organization of the Periodic Table
The table forms horizontal rows called periods.
Their periodic relationship is seen in the modern table
shown below.
A.10 – Organization of the Periodic Table
(continued)
Each of the columns is called a group or family, due to
their similar properties
A.10 – Organization of the Periodic Table
(continued)
The alkali metal family is the six (6) elements in the
first column starting with Lithium
A.10 – Organization of the Periodic Table
(continued)
The noble gas family is the six (6) elements in the
rightmost column which are unreactive, chemically inert
elements.
A.10 – Organization of the Periodic Table
(continued)
The halogen family is the five (5) elements immediately
to the left of the nobles that readily form ions.
A.11 – Predicting Properties
Using the periodic chart we can
predict properties of the various
elements.
A.11 – Predicting Properties
(continued)
1) Given, the b.p. of argon (Ar) is -186°C and of
xenon (Xe) is -112°C. Estimate the b.p. of
krypton (Kr).
Krypton should
have a boiling
point between
argon 87 K and
xenon 161 K of
about 124 K –
actual = 120 K.
A.11 – Predicting Properties
(continued)
2a) Given, the m.p. of potassium (K) is 337°K and
of cesium (Cs) is 302°K. Estimate the m.p. of
rubidium (Rb).
Actual = 312 K
2b) Would the
m.p. of sodium
(Na) be higher
or lower than
(Rb) , explain.
A.11 – Predicting Properties
(continued)
3) Known, silicon tetrachloride exists (SiCl4)
Predict the formula for Ge and Cl.
GeCl4
A.11 – Predicting Properties
(continued)
4) Known, the following exist : NaI, MgCl2, CaO,
Al2O3, and CCl4
Predict the combination
a) C and F
CF4
A.11 – Predicting Properties
(continued)
4) Known, the following exist : NaI, MgCl2, CaO,
Al2O3, and CCl4
Predict the combination
b) Al and S
Al2S3
A.11 – Predicting Properties
(continued)
4) Known, the following exist : NaI, MgCl2, CaO,
Al2O3, and CCl4
Predict the combination
c) K and Cl
KCl
A.11 – Predicting Properties
(continued)
4) Known, the following exist : NaI, MgCl2, CaO,
Al2O3, and CCl4
Predict the combination
d) Ca and Br
CaBr2
A.11 – Predicting Properties
(continued)
4) Known, the following exist : NaI, MgCl2, CaO,
Al2O3, and CCl4
Predict the combination
e) Sr and O
SrO
HW 8
Read & take notes on sections A.12
A.12 – What Determines Properties?
Major difference between metals
and nonmetals is that metal
atoms lose electrons more
easily.
A.12 – What Determines Properties?
(continued)
Some physical properties of metals
depend on attractions among their
atoms. Stronger attractions =
higher melting points
m.p. of Mg is 650°C
m.p. of Na is 98°C
A.12 – What Determines Properties?
(continued)
Understanding properties of the chart
is the key to predicting – this allows
chemists to create new chemical
compounds to meet specific needs.
Predicting Properties
Periodic Chart of Elements Online
Link http://www.ptable.com/
HW 9
See the next slide
A.13 – It’s Only Money
Address questions 1-6 on pg 127.