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< 1 nm
solutions
transparent
(clear)
molecular motion
never settle
> 100 nm
colloids
transparent with
Tyndall effect
(scattering of light)
coagulation – can settle
suspensions
translucent
(cloudy)
movement by
gravity
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Tyndall Effect?
< 1 nm
solutions
Absorption
Passage of of
light
light
> 100 nm
colloids
Scattering in beam
suspensions
Scattering in
all directions
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Does a chemical reaction take place
when one substance dissolves in
another?
No, dissolving is a physical
change because no new
substances are formed.
When one substance
dissolves in another,
the resulting mixture is
called a solution.
4
Solutions
Does a chemical reaction
take place when one
substance dissolves in
another?
No, dissolving is a
physical
change because no
new
substances are
formed.
When one substance
dissolves in another,
the resulting mixture is
called a solution.
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Some Definitions
A solution is a
HOMOGENEOUS
_______________
mixture of 2 or more
substances in a
single phase.
One constituent is
usually regarded as
the SOLVENT and
the others as
SOLUTES.
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Parts of a Solution
Solute
• The substance
that is dissolved
• The substance
present in a
smaller amount
Solvent
• The substance that
dissolves the solute
• The substance that is
present in the greater
amount
• The solvent
determines the state of
the solution
Solute + Solvent = Solution
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8
“Like dissolves like”
–Polar dissolves in polar and ionic
Ex. Sugar and Water
–Non-polar dissolves in non-polar
Ex. oil and soap
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The solute breaks up into tiny particles that spread
evenly throughout the solvent. In a solution of sugar
water, sugar is the solute, and water is the solvent.
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Are all solutions liquids?
• No! Many types of solutions are possible.
Let’s talk about a few examples.
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Alloy- a mixture done by the melting of two or more metals
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How do I get
solutes to dissolve
faster in
solvents? Ex.
Sugar in iced tea?
Stir, and stir, and stir
Fresh solvent contact and interaction with solute
Add temperature
Faster rate of dissolution at higher temperature
Grind the solute to make it smaller
Greater surface area, more solute-solvent interaction
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SOLUBILITY
• Definition: The maximum amount of solute
that will dissolve in a given amount of solvent
at a specified temperature and pressure.
• Soluble- the solute can be completely
dissolved in the solvent
• Insoluble- the solute cannot be dissolved in
the solvent. In fact, it separates completely.
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Miscible vs. Immiscible
• When two liquids
totally mix they are
said to be
miscible.
• When two liquids
do not mix they are
said to be
immiscible.
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Dissolving process in water
When particles of the solute are completely dispersed and
surrounded by particles of the solvent, this process is
called SOLVATION.
Na+
Cl-
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The separation of the ions in an ionic compound (usually by
dissolving water) is called DISSOCIATION
For water: POLAR-POLAR
For hydrated ion:
Ion-polar
Na+
ClFor NaCl (s): ion-ion
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IONIZATION
• The physical process of converting an atom
or a compound into ions by adding or
removing electrons. Usually done by a
solvent in a solution.
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Definitions
Solutions can be classified as
saturated or unsaturated.
A saturated solution-Contains
the maximum quantity of
solute that dissolves at that
temperature.
An unsaturated solutionContains less than the
maximum amount of solute
that can dissolve at a
particular temperature
Definitions
SUPERSATURATED SOLUTIONS
contain more solute than is
possible to be dissolved
Supersaturated solutions are
unstable. The supersaturation is
only temporary, and usually
accomplished in one of two ways:
1. Warm the solvent then cool the
solution
2. Evaporate some of the solvent.
http://www.youtube.com/watch?v=XSGvy2FP
fCw
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Supersaturated
Sodium Acetate
• One application
of a
supersaturated
solution is the
sodium acetate
“heat pack.”
Aqueous Solutions
(water is the solvent)
How do we know ions are present in
aqueous solutions?
If the solution
conducts electricity
it is called an ELECTROLYTE
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22
Types of solutes
high conductivity
Strong Electrolyte 100% dissociation,
all ions in solution
Na+
Cl-
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Types of solutes
slight conductivity
Weak Electrolyte partial dissociation,
molecules and ions in
solution
CH3COOH
H+
CH3COO-
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Aqueous Solutions
Some compounds dissolve in water but
do not conduct electricity. They are
called NONELECTROLYTES.
Examples include:
sugar
ethanol
ethylene glycol
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Types of solutes
no conductivity
Non-electrolyte No dissociation,
all molecules in
solution
sugar
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Electrolytes in the Body
 Carry messages to
and from the brain
as electrical signals
 Maintain cellular
function with the
correct
concentrations
electrolytes
Make your own
50-70 g sugar
One liter of warm water
Pinch of salt
200ml of sugar free fruit
squash
Mix, cool and drink
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Concentration
• The measure of how much solute is dissolved
in a specific amount of solvent or solution.
• Concentrated large amount of solute high
Molarity
• Diluted small amount of solute low
Molarity
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Percent by Mass
• The ratio of the solute’s mass to the
solution’s mass expressed as a percent.
Percent by Mass = mass of solute
X 100
mass of solution
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Calculating Percent by mass
• What is the percent by mass of NaHCO3 in a
solution containing 20 g NaHCO3 dissolved in
600 ml of H2O?
Unknown
% mass NaHCO3
% mass = mass solute X 100
Formula
mass solution
Given 20 g NaHCO3  solute
600 ml H2O  solvent
Implied 1 ml H2O = 1 g H O  600 g H O
2
2
% mass = 20g NaHCO3 X 100
620 g H2O
= 3%
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Your turn
• You have been given 3.6 g NaCl that you then
dissolve in 525 g of water. What would be the
percentage by mass of NaCl?
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Molarity
• The number of moles of solute dissolved in
per liter of a solution.
moles
solute
Molarity(M) = liters of solution
Molarity = moles of solute = mol
liters of solution
L
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Calculating Molarity
• What is the molarity of an aqueous solution
containing 40.0 g of glucose (C6H12O6) in a
1500 ml solution?
• If given 340 g of CuCl2, what would be the
molarity of the solution if it was dissolved in
6425 cm3 of water? Note: (1 cm3 = 1 ml)
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molality
• Since the volume of a solution changes as
temperature changes, the Molarity of the
solution changes as well. Therefore,
sometimes it is more useful to use molality.
mol solute
Molality (m) =
kilograms solvent
Note 1 Kg= 1000 g
• Why? Because masses do not change with
temperature!
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Calculating molality
• What is the molality of a solution containing
10.0 g Na2SO4 dissolved in 1000.0 g of water?
• What is the molality of a solution containing
30.0 g of naphthalene (C10H8) dissolved in
500.0 g of toluene?
Practice Problems
• Calculate the percent by mass of 3.55 g
NaCl dissolved in 88 g water.
• Calculate the percent by mass of
benzene in a solution containing 14.2 g
of benzene in 28.0 g of carbon
tetrachloride.
• What is the molarity of the following
solutions?
– 15.25 g MgCl2 in 500 mL of solution
– 2.48 g CaF2 in 375 cm3 of solution
• Calculate the molality of the following
solutions:
– 20.0 g CaCl2 in 700.0 g H2O
– 3.76 g NaOH in 0.850 L H2O
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