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Chemistry is the study of matter, its properties and its changes or
transformations.
Matter
Pure
Substances
Mixtures
Solutions
Compounds
Mechanical
Mixtures
Elements
Matter is something that has mass and occupies space (has
volume).
A pure substance is a kind of matter that cannot be separated into
other kinds of matter by any physical process.
A mixture is a composition of two or more pure substances (not
chemically bonded) with each other and are capable of being
separated.
An element is a substance (homogenous) made up of one type of
atom.
A compound is a substance (homogenous) made up of one type
of molecule or formula unit.
A solution (homogenous mixture) is a mixture that displays one
phase.
A mechanical mixture (heterogeneous mixture) is a mixture that’s
displays two or more phases.
Examples
Elements:
Compounds:
Solutions:
Mechanical Mixtures:
Solutions and Mechanical Mixtures can be hard to distinguish.
Liquid or gaseous solutions are transparent while mechanical
mixtures are not (display the Tyndall effect).
(air, pop, hydrogen in Pt, sea water, gasoline, dental amalgams (Hg in Ag), Brass (Cu, Zn), Bronze (Cu, Sn), solder (Sn, Pb))
(Suspensions: penicillin, Peptobismol, Milk of Magnesia, salad dressing, milk, paint
colloids: whipped cream, shaving cream, )
Solutions are made up of a solvent which is the substance that
dissolves one or more solutes. A solution retains properties from
the solute and the solvent.
Mechanical mixtures are heterogeneous which means that you
can see the different particles in them (two or more phases). Two
types of these mixtures seem homogenous but upon closer
inspection are not. In a suspension the particles may be seen with
the unaided eye or through a microscope. Over time gravity will
cause the suspended particles to separate. If the suspended
particles are small enough gravity will not cause the particles to
separate. This type of mixture is a colloid.
Mixtures are separated by physical means such as evaporation,
distillation, freezing, filtration, flotation). Elements can only be
broken down by nuclear reactions while compounds can only be
broken down by chemical reactions)
States of Matter
There are three states of matter: solid, liquid and gas.
Please sketch 20 water molecules in the ice form in a beaker.
Next sketch 20 water molecules in the liquid form in a
different beaker. Finally repeat this sketch for 20 molecules of
water in the steam form.
Matter Drawings
Sketch 20 solid iron atoms. Sketch a solution of 20 water
molecules and 10 sugar molecules. Sketch a mechanical
mixture of 20 water molecules and 20 oil molecules before
and after shaking.
Physical Properties
A property is a quality or characteristic.
- a diamond is hard
- iron rusts
The physical properties of a substance are those properties
which can be determined without changing its composition or
make-up. Physical properties include colour, odour, length,
area, volume, mass, hardness, melting and boiling point,
conductivity, solubility, and density.
Mercury is an odourless liquid with a silvery shine. It does not
dissolve in water. It is an excellent conductor of electricity. It
freezes at -39o C and boils at 357o C.
Chemical Properties
The chemical properties of a substance are those properties which can be
determined only when a substance undergoes a change in composition
(chemical reaction).
Gold is difficult to distinguish from fool’s gold. Fool’s gold reacts with nitric
acid while gold does not. Carbon burns in air to produce carbon monoxide
and carbon dioxide. Carbonic acid decomposes into water and carbon
dioxide.
A substances reactivity can be broken down into a few areas. Reactivity
with other substances, combustibility, stability and toxicity are some of
these areas.
Quantitative and Qualitative Properties
A quantitative property is one that can be measured. Numbers will be
used in expressing a quantitative property.
Qualitative properties are those which cannot be expressed numerically.
Examples include appearance and odour.
Physical Change
A physical change is a change which alters one or more
properties of the substance with no change in its composition
or identity.
-freezing, melting, boiling, condensing, evaporation,
sublimation, breaking, tearing, bending, flattening
What properties of the substance change in the following
physical changes: melting, boiling, breaking, bending?
Chemical Change
A chemical change is a change in a substance which
converts it into a different kind (or different kinds) of matter
(each with a different composition and new properties).
PENPEN
proton
electron
neutron
location
nucleus
orbit
nucleus
charge
+1
-1
0
mass
1u
0u
1u
an electron actually weight 1/1876 u but we treat this as 0 u for our purposes
A
Z
X is the element symbol
A is the atomic mass in atomic mass units (u)
Z is the atomic number (number of protons)
b is the electric charge
c is the number of atoms
Remember these simple rules for analyzing elements.
#p+
+
#p+ +
#e-
= b
#no = A
X
b
c
11
B
5
19
9
1
1
F
H
28
14 Si
238
92U
2
1
3
1
H
Hydrogen deuterium
H
tritium
-only hydrogen has names for its isotopes
24
12
Mg
12
6
+
2
C
6 p , 4e-, 6no
25
12
Mg
37
3
17 Cl
26
12
Mg
197

Au
79
+
o
17 p+, 20e- , 20no79 p , 78e , 118n
-try the PEN sheet
-the # of p+ determines which element it is
Average Atomic Mass
Naturally occurring elements are made up of different isotopes.
The mass of an element found on a periodic table is the average
atomic mass. It can be calculated by a weighted average of the
isotope masses and their percentage natural occurrence.
24
12
Mg
78.7%
25
12
Mg
10.13%
26
12
Mg
11.17%
Average  24(0.787)  25(0.1013)  26(0.1117)
Average  24.32 u
These calculations may not agree exactly with the average atomic mass on the periodic
table because the isotope masses above are not exact. When making an atom from
protons and neutrons mass is lost in the fusion or fission reaction.
The Periodic Table
The Periodic Table has gone through many forms to its present
day arrangement. Today the only changes that are possible for the
future are the addition of more elements.
There are various levels of organization in the Periodic Table of
your textbook. Try and answer these questions to discern this
organization.
How are gaseous, liquid and solid elements displayed?
How are metals, non-metals and metalloids displayed.
The highlight of the Periodic Table is the organization of elements
in families or groups (vertical columns). These families have
similar Lewis Dot diagrams and display similar chemical
properties.
Lewis Dot Diagrams
In some ways chemistry can be thought of as how atoms interact
with other atoms. The outer shell electrons or valence electrons
are the most important part of this interaction. Lewis Dot Diagrams
show the valence electrons of an atom. The pattern of valence
electrons is the fundamental pattern that determines chemical
reactivity.
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
The fourth period is 18 elements wide however the patterns set up
in the second and third rows continue for the rest of the periodic
table. The transition metal electrons do enter the outer shell but
drop down a level upon leaving the transition metal area. The loss
of these ten electrons means that once again the inert gases need
eight electrons in their outer shell. Lewis Dot Diagrams are not
drawn for transition metal elements.
K
Ca
Rb Sr
Ga
Ge
As
Se
Br
Kr
In
Sn
Sb
Te
I
Xe
Ions
An ion is an electrically charged atom or group of atoms. Atoms
lose or gain electrons to have a full outer shell. They become
isoelectronic with the nearest Noble gas. This full outer shell is a
more stable arrangement than the neutral atom. Noble gases do
not form ions because they are already quite stable with a full
outer shell.
Every atom has two choices (full or empty) but the choice which
involves gaining or losing the least electrons forms the preferred
ion.
Hydrogen can lose or gain one electron to become stable (H+ or
H-) however the positive hydrogen ion (p+ or H+) is much more
common.
Carbon and all other members in its group can lose or gain four
electrons to become stable, however since this involves so many
electrons neither positive or negative ion is common.
Li+ Na+
Be+2 Mg+2
K+
Rb+
Ca+2 Sr+2
Cs+
Ba+2
B+3
Al+3
Ga+3 In+3
Tl+3
F-
Cl-
Br-
I-
At-
O-2
S-2
Se-2
Te-2
Po-2
N-3
P-3
As-3
Sb-3
Bi-3
Separating mixtures, conservation of mass, constant
composition, evidence of chemical change