Aqueous
Systems and
Solutions
Newport High School
General Chemistry
Mrs. Teates
Lesson 1
Water and it’s Properties

Essential Questions:
–
–
How can you account for the high surface
tension and the low vapor pressure of water?
How would you describe the structure of ice?
•70% of the Earth’s surface is covered in water
Water Fast Facts
Water is found as a vapor, liquid, and solid
(ice).
 Your drinking water comes from either
ground water or surface water.
 Pure water is clear, odorless, and tasteless.
– The taste and odor of water from your tap
comes from substances dissolved in
water.
 Water is a simple triatomic polar molecule.

The Water Molecule
δ is the lowercase Greek symbol delta
δ+water
means
a a
Thus,
has
δ- means a
partial
partial
negative end
partial
positive
(0xygen)
and a
negative
charge
partial
positive end
δcharge
(Hydrogen) – and it
O
is called “polar”
H
H
because of these
δ+
areas of difference δ+
The Water Molecule
Properties of Water
 Water’s
bent shape and ability to
hydrogen bond gives it many
special properties!
–High surface tension
–Low vapor pressure
 Water molecules are attracted to one
another by dipole interactions.
High Surface Tension



Liquid water acts like it
has a “skin.”
– Glass of water
bulges over the top
Water forms round
drops
– Spray water on
greasy surface, what
do you see?
All because water
hydrogen bonds.
Surface Tension
One water molecule
can hydrogen bond to
another because of
this electrostatic
attraction.
 Also, hydrogen
bonding occurs with
other molecules
surrounding them on
all sides.
d-

H
d+
d+
d-
H
d+
d+
Surface Tension
Water
molecule at the surface
is only pulled down and to the
sides.
Holds
the molecules at the
surface together tightly.
This
causes surface tension.

A water molecule in the
middle of a solution is
pulled in all directions.
Surface Tension
 Water
drops are
rounded,
because all
molecules on
the edge are
pulled to the
middle- not
outward to the
air!
Meniscus





Glass has polar molecules, which also
means it can hydrogen bond.
This attracts water molecules and pulls
some of them up the sides.
Water curves up along the side of glass.
This makes the meniscus, as in a
graduated cylinder
Plastics are non-wetting; no attraction
Water
Plastic
Surface tension
 All
liquids have surface tension
–water is just higher than most others
 How can we decrease surface tension?
–Use a surfactant - surface active
agent
• Also called a wetting agent, like detergent or soap
• Interferes with hydrogen bonding
Low vapor pressure
• Hydrogen bonding also explains water’s
unusually low vapor pressure.
–Holds water molecules together, so
they do not escape easily
–This is a good thing, because lakes
and oceans would evaporate very
quickly due to their large surface
area!
Quick Lab
•In this lab you will investigate the properties
of surfactants and surface tension.
Ice

Most liquids contract (get smaller) as they are
cooled.
– They get more dense.
– Solid metals sink in their own liquid metal.
– But, ice floats in water.

Water becomes more dense as it cools, until it
reaches about 4ºC.
– Then it becomes less dense by starting to expand (Want your
water pipes to freeze in the winter?)
Liquid – random shaped
arrangement
Solid – honeycomb
shaped arrangement
O
Ice

Water freezes from the top
down.
– The layer of ice on a pond acts as
an insulator for water below.

A considerable amount of
energy is required to return
water in the solid state to the
liquid
– The heat absorbed when 1 g of
water changes from solid to liquid
is 334 J.
– This is the same amount of energy
needed to raise the temperature of
1 g of liquid water from 0 oC to 80
oC!
Lesson 2 – Aqueous Solutions
 Essential
Questions:
– How do solutes and solvents behave
in solution?
– How does the presence of
electrolytes change a solution?
– What is the difference between a
suspension, a solution, and a colloid?
Solvents and Solutes
Definitions
 Solution
- a homogenous mixture, that is
mixed molecule by molecule.
 Solvent
- the dissolving medium
 Solute
- the dissolved particles
 Aqueous solution - a solution with water
as the solvent.
Parts of a Solution:
1. Solute
A solute is the dissolved substance in a
solution.
Salt in salt water
Sugar in soda drinks
Carbon dioxide in soda drinks
2. Solvent
A solvent is the dissolving medium in a
solution.
Water in salt water
Water in soda
Concentrated vs. Dilute
Aqueous Solutions
Water dissolves ionic compounds and
polar covalent molecules best.
 The rule is: “like dissolves like”
 Polar dissolves polar.
 Nonpolar dissolves nonpolar.
 Oil is nonpolar.
– Oil and water don’t mix.
 Salt is ionic- makes salt water.

The Solution Process



Called “solvation”.
Water breaks the + and charged pieces apart and
surrounds them.
In some ionic compounds,
the attraction between
ions is greater than the
attraction exerted by
water
How Ionic solids dissolve in water
These ions have been pulled away from the
main crystal structure by water’s polarity.
H
H
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/thermochem/sol
utionSalt.html
H
H
H
These ions have been
surrounded by water,
and are now dissolved!
Solids will dissolve if the attractive force
of the water molecules is stronger than
the attractive force of the crystal.
 If not, the solids are insoluble.
 Water doesn’t dissolve nonpolar
molecules (like oil) because the water
molecules can’t hold onto them.
 The water molecules hold onto other
water molecules, and separate from the
nonpolar molecules.
 Nonpolars? No repulsion between them

Electrolyte vs. Nonelectrolyte

Electrolyte – substance that
dissolves in water to give a
solution that conducts electricity
– All ionic compounds
– substance
that dissolves in water to give a
solution that does not conduct
electricity
Nonelectrolyte
Electrolyte vs. Nonelectrolyte
-
-
+
sugar
-
+
acetic acid
NonElectrolyte
Weak
Electrolyte
Solute exists as
molecules only
(Molecular
compounds)
Solute exists as
ions and
molecules
(Ionic compounds
and molecular
compounds)
View animation online.
+
salt
Strong
Electrolyte
Solute exists as
ions only
(Ionic compounds
only)
Electrolyte Summary


Electrolyte
– Substances that conduct electricity when dissolved in
water, or molten.
– Ionic compounds break into charged ions:
NaCl Na1+ and Cl1– These ions can conduct electricity.
– Weak electrolytes don’t fall completely apart into
ions.
– Strong electrolytes do ionize completely.
Nonelectrolyte
– Do not conduct electricity when dissolved in water
– Polar covalent molecules such as methanol (CH3OH)
Mixtures that are NOT Solutions
Suspensions: mixtures that slowly settle
upon standing.
– Particles of a suspension are greater in
diameter than 1000 nm.
– Can be separated by filtering (p.459)
 Colloids: heterogeneous mixtures with
particles between the size of suspensions
and true solutions (1-1000 nm)

Types of Mixtures
Solutions
Colloids
Suspensions
Homogeneous
Heterogeneous
Heterogeneous
Do not separate on
standing
Do not separate on
standing
Particles settle out
Cannot be separated by
filtration
Cannot be separated by
filtration
Can be separated by
filtration
Do not scatter light
Scatter light (Tyndall
Effect)
May scatter light, but are
transparent
Examples: (can be solid,
liquid, or gas) oxygen in
nitrogen, carbon dioxide in
water, sugar in water,
copper in nickel
Examples: mayonnaise,
milk, fog, mist, cheese,
butter, gelatin, shaving
cream, smoke, airborne
particulate matter, glue
Examples: muddy water,
clay in water
Colloids and
suspensions scatter
light, making a beam
visible, due to their
large particle size.
Solutions do not
scatter light, because
of their small particle
size.
The Tyndall Effect
colloid
solution
Example: Headlights Which glass contains a colloid?
on a foggy night.
- Page 461
Note that you can easily see the “sunbeam”, probably due
to the presence of fog in the forest
Mixtures that are NOT Solutions
 Brownian
Motion
–Flashes of light are seen when
colloids are studied under a
microscope
–To describe the chaotic movement of
the particles.
–Observed by Robert Brown.
Mixtures that are NOT Solutions
Emulsions- dispersions of liquid in liquid (2
immiscible liquids + an emulsifier)
– an emulsifying agent is essential for
maintaining stability; it has one polar end,
and the other end is nonpolar
– oil and water not soluble; but with soap or
detergent added, they will be.
 Oil + vinegar in dressing – are they soluble?
– What makes up Mayonnaise? Margarine?

Lesson 3 – Properties of
Solutions
 Essential
Questions:
– How are solutions
formed?
– What factors
determine
solubility?
Solution formation


The “nature” (polarity or composition) of
the solute and the solvent will
determine…
1. Whether a substance will dissolve
2. How much will dissolve
Factors determining rate of solution...
1. Stirring (agitation)
2. Surface area the dissolving particles
3. Temperature
Making solutions
In order to dissolve, the solvent molecules
must come in contact with the solute.
1. Stirring moves fresh solvent into contact
with the solute.
2. Smaller pieces increase the amount of
surface area of the solute.
- Think of how fast a breath mint
dissolves when you chew it.
Temperature and Solutions
3. Higher temperature
makes the
molecules of the
solvent move
around faster and
contact the solute
harder and more
often.
–
–
Speeds up dissolving.
Usually increases
amount that will
dissolve.
How Much?
 Solubility-
is the maximum amount of substance
that will dissolve at a specific temperature (the
units for solubility are: g solute/100 g solvent)
 Unsaturated solution- Can still dissolve more
solute (for example 28.0 g NaCl/100 mL)
 Saturated solution- Contains the maximum
amount of solute dissolved.
NaCl = 36.0 g/100 mL water
 Supersaturated- solution that is holding more
than it theoretically can
Solubility
UNSATURATED
SOLUTION
more solute
dissolves
SATURATED
SUPERSATURATED
SOLUTION
SOLUTION
no more solute becomes unstable,
dissolves
crystals form
concentration
Saturation and Equilibrium
Solute is More solute is dissolving, Saturation
dissolving but some is crystallizing equilibrium
established
Supersaturated Example




Ever heard of “seeding” the clouds to make them
produce rain?
Clouds - mass of air supersaturated with water
vapor
Silver Iodide (AgI) crystals are dusted into the
cloud as a “seed”
The AgI attracts the water, forming droplets that
attract others
Liquids
 Miscible
means that two liquids can
dissolve in each other
–water and antifreeze
–water and ethanol
 Partially miscible- slightly
–water and ether
 Immiscible means they can’t
–oil and vinegar
Solubility?
 For
solids in liquids, as the temperature
goes up-the solubility usually goes up
 For gases in a liquid, the effect is the
opposite of solids in liquids
–As the temperature goes up, gas solubility
goes down
–Think of boiling water bubbling?
–Thermal pollution may result from industry
using water for cooling
Gases in liquids...
 Henry’s
Law - says the solubility of a gas
in a liquid is directly proportional to the
pressure of the gas above the liquid
–think of a bottle of soda, removing the
lid releases pressure
 Equation:
S1
S2
=
P1
P2
Sample 16.1, page 477
Lesson 4 – Concentrations of
Solutions

Essential Questions:
– What is molarity?
– What effect does dilution have on the
molarity of the solution?
Concentration is...
a
measure of the amount of solute
dissolved in a given quantity of solvent
 A concentrated solution has a large
amount of solute
 A dilute solution has a small amount of
solute
–These are qualitative descriptions
 But, there are ways to express solution
concentration quantitatively
Concentrated vs. Dilute
Molarity
Molarity
= moles of solute
liters of solution
• Abbreviated with a capital M,
such as 6.0 M
• This is the most widely used
concentration unit used in
chemistry.
- Page 481
Making solutions
1) Pour in a small amount of the
solvent, maybe about one-half
2) Then add the pre-massed solute
(and mix by swirling to dissolve it)
3) Carefully fill to final volume.
– Fig. 16.8, page 481
 Can also solve: moles = M x L
 Sample Problem 16.3, page 482
Dilution
• Adding water to a solution will reduce the
number of moles of solute per unit volume
• but the overall number of moles remains
the same!
• Think of taking an aspirin with a small glass
of water vs. a large glass of water
• You still have one aspirin in your body,
regardless of the amount of water you
drank, but a larger amount of water
makes it more diluted.
Dilution
 The
number of moles of solute in solution
doesn’t change if you add more solvent!
 The # moles before = the # moles after
 Formula for dilution: M1 x V1 = M2 x V2
 M1 and V1 are the starting concentration
and volume; M2 and V2 are the final
concentration and volume.
 Stock solutions are pre-made solutions to
known Molarity. Sample 16.4, p.484
Percent solutions can be expressed
by a) volume or b) mass
 Percent
means parts per 100, so
 Percent by volume:
= Volume of solute x 100%
Volume of solution
 indicated %(v/v)
Sample
Problem 16.5, page 485
 Percent
Percent solutions
by mass:
= Mass of solute(g)
x 100%
Volume of solution (mL)
 Indicated %(m/v)
 More commonly used
 4.8 g of NaCl are dissolved in 82 mL of
solution. What is the percent of the
solution?
 How many grams of salt are there in 52
mL of a 6.3 % solution?
Lesson 5 – Colligative
Properties

Essential Question:
– What are the colligative properties of
a solution?
Colligative Properties
-Depend only on the number of
dissolved particles
-Not on what kind of particle
-Three important colligative
properties are:
1) Vapor pressure lowering
2) Boiling point elevation
3) Freezing point lowered
- Page 488
Colligative Properties
CaCl2 will have
three particles in
Glucose will only
NaCl will have two
have one particle in particles in solution solution for each
solution for each one for each one particle one particle it
starts with.
particle it starts with. it starts with.
Vapor Pressure is lowered
 The
bonds between molecules keep
molecules from escaping.
 In a solution, some of the solvent is busy
keeping the solute dissolved.
 Lowers the vapor pressure
 Electrolytes form ions when they are
dissolved, making more pieces.
 NaCl  Na+ + Cl- (= 2 pieces)
 More pieces = bigger effect
Boiling Point is Elevated
 The
vapor pressure determines the
boiling point.
 Lower vapor pressure means you need a
higher temperature to get it to equal
atmospheric pressure
 Salt water boils above 100ºC
 The number of dissolved particles
determines how much, as well as the
solvent itself.

Boiling Point Elevation Simulation
Boiling Point Elevation
Solute particles weaken IMF in the solvent.
Freezing Point is Lowered
 Solids
form when molecules make
an orderly pattern - crystals
 The solute molecules break up the
orderly pattern.
–Makes the freezing point lower.
–Salt water freezes below 0ºC
 How much lower depends on the
amount of solute dissolved.
Freezing Point Depression
View Flash animation.
- Page 494
The addition of a solute would allow a larger temperature
range, since freezing point is lowered and boiling point is
elevated.
Lesson 6 – The Riverwood
Fish Kill

Essential Questions:
– What are the possible sources for the
fish kill?
– What should be done to correct this
problem?
Class Activity
Each group will become an expert on a
certain section in the packet and will be
responsible for teaching others in the
class about your particular section.
 In class you will be creating a poster
with the necessary notes that everyone
in the class should know about your
topic.
– Be sure to include pictures as well.
 You will have this class period to gather
your notes and prepare your poster.

Group Topics
Inappropriate Heavy-Metal Ion
Concentrations
 Inappropriate pH levels
 Inappropriate Molecular-Substance
Concentrations
 Inappropriate Dissolved Oxygen Levels
 Temperature, Dissolved Oxygen, and
Life

 What
caused the fish kill?
 Was a single factor
responsible?
 Are patterns are present in
data?
 What limits are exceeded or
approached?
Possible Causes of Fish Kill
 Water
 Dissolved
temperature
 Dissolved
oxygen
 Rainfall
 Water flow
molecular
substances
 pH
 Nitrate and
phosphate levels
 Organic carbons
 Heavy metals
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Data Graphs – Water Flow
Snake River Water Flow(cubic feet per sec)
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
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Water Temperature
Water Temperature(C)
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
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Dissolved Oxygen
Dissolved Oxygen(ppm)
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
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Rainfall
Rainfall (mm)
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
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pH Levels
pH of Snake River
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
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Organic Carbon
Organic Carbon (ug/L)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
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Lead
Lead (ug/L)
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
3.0
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Heavy Metals
Heavy Metals
3.5
Cadmium (ug/L)
Mercury (ug/L)
Arsenic (ug/L)
2.5
2.0
1.5
1.0
0.5
0.0
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Se ugu
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em
b
O er
ct
ob
er
ay
Ju
ne
M
Nitrate
Nitrate (ppm)
0.250
0.200
0.150
0.100
0.050
0.000
Ju
Au l y
S e gu
pt st
em
b
O er
ct
N ob
ov e
e r
D mb
ec e
em r
b
J a er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
Au l y
Se g
pt ust
em
b
O er
ct
N ob
ov e
e r
D mb
ec e
em r
b
J a er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
Au l y
Se g
pt ust
em
b
O er
ct
ob
er
ay
Ju
ne
M
Phosphate
Phosphate (mg/L)
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
0.25
Ju
Au ly
Se g u
pt st
em
b
O er
ct
N ob
ov er
e
D mb
ec er
em
b
Ja er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
A ly
Se ugu
pt st
em
b
O er
ct
N ob
ov er
e
D mb
ec er
em
b
Ja er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
Au ly
Se g u
pt st
em
b
O er
ct
ob
er
ay
Ju
ne
M
Pesticides and PCBs
Pesticides and PCB's
0.5
0.45
0.4
0.35
0.3
Pesticide (mg/L)
PCB's(ug/L)
0.2
0.15
0.1
0.05
0
4.0
Ju
Au l y
S e gu
pt st
em
b
O er
ct
N ob
ov e
e r
D mb
ec er
em
b
J a er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
Au l y
S e gu
pt st
em
b
O er
ct
N ob
ov e
e r
D mb
ec er
em
b
J a er
nu
Fe ary
br
ua
r
M y
ar
ch
Ap
ril
M
ay
Ju
ne
Ju
Au l y
S e gu
pt st
em
b
O er
ct
ob
er
ay
Ju
ne
M
Dissolve Oxygen - Temperature
DO vs Temperature
16.0
14.0
12.0
10.0
8.0
6.0
Water Temperature(C)
Dissolved Oxygen(ppm)
2.0
0.0
Lesson 7 – Water Purification
& Treatment

Essential Questions:
– What is water purification important?
– What are the different methods of
water purification?
Two
Main Treatments
–Hydrological Cycle
Purification
–Municipal Water Treatment
Hydrologic Cycle
Hydrologic Cycle

Purification Steps
– Evaporation and
Condensation
• Removes nearly all
dissolved
substances
– Bacterial Action
• Converts nearly all
organics
– Filtration
• Removes suspended
matter

Problems
– Easy to overload
system
– Needs long “hold
up” time to be
effective
– Acid water
• dissolves minerals
magnesium,
calcium
Municipal Water Treatment
Created to treat water supplies for a
community, not individual wells.
 Ground and surface water have
different types of contamination.
 Laws have been created to monitor this.
– Clean Water Act
– DEP drinking water
– EPA drinking water

Water Sources

Surface Water
– Lakes
– Run-off from
melting snow
– Springs

Ground Water
– Aquifers
– Well water
Ground Water
Surface Water
Surface Water

Treatment conditions – primarily directed
towards microbial concerns
– Use of chlorination has been the preferred
method since 1914 because it kills bacteria.

Byproducts – produced by the standard
chlorine disinfection's processes
– THMs (Trihalomethanes are suspected
carcinogens)
• Ways to reduce include activated charcoal filters, using
ozone of ultraviolet light (not approved for municipal
supplies), or eliminate prechlorination of the water.




Ground Water
Most resides in spaces of soils and geologic
formations.
– Some of the water is in soils that contain air and
gas, and cannot be pumped.
Supplies ~50% of California’s water.
Treatment – traditionally directed towards naturally
occurring contaminants leached from the earth
(radon, boron, arsenic, and recently viruses and
bacteria)
Modern problems – greater problems due to
pesticides, herbicides, fertilizers, cleaning solvents,
fuel ingredients)
Ground Water





Contaminants are now starting to appear.
VOC (volatile organic chemicals) include solutions
used in dry cleaning, degreasing machinery.
Pesticides (dibromochloropropane)
Arsenic is a semi-metallic element used in wood
preservatives, herbicides and pesticides.
– Ingestion of 100 mg results in severe poisoning.
Nitrate fertilizers, and livestock wastes contaminate
groundwater.
– Nitrate is essential for protein production in plants.
– High levels in water can cause serious health
problems in infants can be fatal.
– Pro-con: food production -v- environmental.
Bottled vs. Tap Water

Is bottled water really better than tap
water?
– Expense
– Some bottled water comes from
municipal supplies.
– Well water vs. spring water
– Can you tell the difference?
Water Softening

Water containing an excess of hard minerals
(calcium, magnesium, iron, etc.) needs to be
softened.
Water Softener

Softeners are often
in individual homes
and can make the
water taste better,
keep clothes from
turning brown, and
extend the life of
faucets and other
plumbing fixtures.
Effects of Hard Water
One Last Note
Water treatment and purification can
remove many substances, but not all.
 Many pharmaceuticals have been found
in the drinking water lately.
– Drugs in the Drinking Water
 What are the side effects of these
pharmaceuticals that cannot be
removed from the water?

Water Treatment Lab
In this lab you will be creating your own
drinking water treatment plant.
 You will be analyzing the ions and other
substances in the solution as the
treatment proceeds.

Works Cited
Prentice Hall Chemistry Textbook
 Chemistry in the Community Textbook
 www.nclark.net
 http://mrsj.exofire.net/chem/
 http://cottonchemistry.bizland.com/chem
/chemnotes1.htm
 http://www.unit5.org/chemistry/
