Arnoldi / Lazaar
Chem Com
Unit One Section C Part Two
Reading Activity
The purpose of this unit is to identify what caused the fish kill in
Riverwood’s Snake River. Often when fish die, it is a result of something being
dissolved in the water. Because water is the
universal
solvent, it can dissolve
many compounds.
Section C.8
p. 65 – 67
Inappropriate Heavy Metal Ion Concentrations
1. What is a “heavy” metal?
A Heavy Metal is an atom that has a greater
mass
than essential metal
elements. Essential elements are those elements that must be ingested, (eaten),
because our body cannot manufacture them. Examples of essential metals include
Iron, potassium, calcium and magnesium.
2. Common Heavy Metals
The two most common heavy metals in our environment are
mercury.
They are the most dangerous to us because they are widely
used
dispersed
and
because they bind to
in our environment.
lead
and
Heavy metals are toxic to humans
proteins in biological systems and then the proteins cannot
function properly. The easiest way to prevent heavy metal poisoning is to not let
them in the water to begin with – once they are in the water it is difficult to get
them out. The food chain exacerbates (makes a lot worse) heavy metal problems
because they cannot be excreted as waste, so they get more
you move up the food chain.
concentrated
as
3. Specific Heavy Metal Problems
One of the two biggest heavy metal problem elements is lead. Products that
have contained lead in the past include paint, pottery, batteries, pesticides.
A second heavy metal problem element is mercury.
mercury include
Products that contained
silent lights switches, thermometers, antiseptic,
fungicides, street lamps.
Mercury enters the body through the
include
skin.
Symptoms of mercury poisoning
numbness, staggering, tunnel vision and brain damage.
Section C.9
p. 68 – 70
Inappropriate pH Levels
1. What is the pH scale?
The pH Scale is a method to report the acidity, basicity,
or
neutral
character of a solution. In other words, the pH scale tells us if a
solution is an acid, a base or is neutral.
2. What are the pH Ranges?
Nearly the entire pH scale is within the range of 0 to 14, although there can
be extreme solutions that do not occur in this range.
anything with a pH of < 7.0 is considered to be a(n)
of > 7.0 is considered to be a(n)
be chemically neutral.
base.
acid.
At room temperature,
Anything with a pH
Anything with a pH = 7.0 is considered to
3. Acid and Base Characteristics
The element found at the beginning of most acids is
polyatomic ion found at the end of most bases is
hydrogen.
hydroxide.
The
Both acids and
bases will conduct electricity when dissolved in water.
4. pH and Fish
Fish can tolerate a pH range from
pH to be <7, which is
Specifically, fish -
acidic.
five to nine.
If pH drops too low,
It is more common for the
reproduction
is impaired.
egg development is impaired.
5. pH and Metal Ion Concentration
If the pH of a water sample drops too low, the metal ion concentration will
increase.
This means more metal ions are dissolved in the water. A special word
for this is leaching, which means they have dissolved more readily.
concentration is a measure of the amount of
Remember,
solute dissolved in a specific amount
of solvent.
6. pH and Drinking Water
The EPA suggests a pH range between
water.
6.5 and 8.5 to ensure safe drinking
Section C.10
pp. 65 – 67 and Solvents Laboratory
Inappropriate Molecular Substance Concentrations
1. What is a molecular substance?
water,
but doesn’t
break up as ions when dissolved in water like ionic substances do.
Molecular
A Molecular Substance is a substance that dissolves in
substances are substances that do not contain ionic bonds, they are covalently
bonded.
In the Solvents Laboratory (Likes Dissolve Likes) we learned that in
covalent bonds electrons are
shared.
This may be uneven sharing, which is a
polar covalent bond, or even sharing, which is a nonpolar covalent bond.
2.
In terms of phases, while ionic compounds are almost always solid at room
temperature, molecular substances are found as
or
solids, liquids,
gases at room temperature.
3. Likes dissolve Likes – an old concept, think about the lab
“Likes Dissolve Likes” is the concept that predicts what substances will
dissolve in each other.
distribution.
EX:
How are substances alike?
It is about
Ionic substances have sides with complete
+ and - charges.
Na+1 and Cl-1  NaCl
In NaCl, the
and the
electron
sodium ion is completely positive,
chloride ion is completely negative.
Polar substances are substances with
shared
partial
charges.
The electrons are
unevenly, so they drift closer to one side or the other.
partially
positive side
This results in a
side (electrons are further away from this atom) and a
partially negative side (electrons drift towards this atom).
EX:
In
water,
the
electrons
partially
negative,
partially
positive
drift
closer
to
making
it
and away from each hydrogen, making them
Nonpolar substances are substances with no charges.
shared
oxygen
The electrons are
evenly, so the charges are perfectly distributed around the molecule, and
no side becomes charged – not even partially.
EX:
In Carbon Dioxide, the electrons are evenly distributed (symmetrical)
around the central atom (C), so this is a nonpolar substance.
EX:
Why does oil, which is nonpolar, not dissolve in water, but it will
dissolve in toluene, which is also nonpolar? Substances want to dissolve in
things that are like them in terms of
e- distribution.
nonpolar, wants to dissolve in a solvent that has no charges
Oil, which is
(water
partial charges - it is polar). So, it won’t dissolve in water. It will
has
dissolve
in toluene which is also nonpolar, and also does not have charges.
So, in summary what do we know? Polar Solutes dissolve in
Nonpolar Solutes dissolve in
nonpolar
polar
solvents.
solvents. Ionic Solutes dissolve in
solvents since ionic solvents do not exist.
charges, but they do have partial charges).
polar
(The polar solvents don’t have total
Section C.12
pp 75 – 79
Inappropriate Levels of Dissolved Oxygen
1. Preview Information
Dissolved oxygen is a molecule of oxygen, O2, in the gas phase.
2. Review Information
(you will need to do Section C Part One before completing this section)
Remember, solubility is the ability of a solute to
dissolve
in a solvent.
Three factors that determine how much of a gas solute can dissolve in the solvent
are:
temperature, pressure,
and the nature of the solvent (this is where
Likes Dissolve Likes comes into play). As temperature rises, gas solubility will go
down, which means less gas will be dissolved.
go
up,
which means
more
As pressure rises, gas solubility will
gas will be dissolved. Ionic compounds dissolve more
readily in water than gases do (gases are covalent compounds).
EX: Why do we keep soda bottles tightly closed? When a soda bottle is
opened, pressure goes
down
which means that
less
gas can stay
dissolved, so the gas (CO2) gets out and the soda goes flat.
3. Temperature, dissolved Oxygen and Life
What is dissolved oxygen?
dissolved in the
water
Dissolved oxygen is the amount of Oxygen
(like Snake River in Riverwood). As temperature increases,
dissolved oxygen levels will go
down.
(It is a gas, as temperature goes up,
solubility goes down. As temperature rises, fish will therefore have
oxygen available and they may suffocate. In addition,
increase as temperature rises.
less dissolved
their
When the metabolism increases,
metabolism
more
oxygen is needed (but it is not there), which makes the problem worse.
dissolved
4. Another organism whose metabolism is affected by increased temperature is
aerobic bacteria, (aerobic = uses oxygen).
This is a problem for fish because if
O2 levels go down, the aerobic bacteria are competing for the
oxygen
fish. Now, there is even less oxygen available in the water for the fish.
with the