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Solutions
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E.Q.: WHAT IS A SOLUTION?
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 substances
in one phase
- Composed of a solvent
and solute (can be more
than one)
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Parts of a Solution
Solute
Solvent
• Dissolves the solute
• Substance
dissolved
• Present in greater
• Present in smaller amount
amount
• Determines the state of
the solution (solid,
liquid, or gas)
Solute + Solvent = Solution
(Homogeneous mixture)
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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….
With your shoulder partner, think of solutions
that are not liquids and be ready to share with
the class your 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?
With your shoulder partner answer the
question and be ready to share with the
class…..
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How do I get
solutes to dissolve
faster in
solvents? Ex.
Sugar in iced tea?
Stirring
Fresh solvent contact and interaction with solute
Increase temperature of solvent
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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The Water Molecule
“The Universal Solvent”
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The Polarity of Water
Water has a simple
molecular structure.
Composed of one
oxygen atom and two
hydrogen atoms.
Each hydrogen atom is
covalently bonded to
the oxygen via a
shared pair of
electrons.
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Electronegativity
• Ability of an atom to attract electrons to itself
while bonding to another atom
• Looking at water, which element has a higher
electronegativity?
OXYGEN
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Since oxygen has a higher electronegativity
than hydrogen:
• Electrons in molecule get closer to oxygen
than with hydrogen
• The oxygen side has a slight or partial
negative charge
• The hydrogen side has a slight or partial
positive charge.
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What does this do to the water molecule????
• The partial positive and negative ends of the
molecule make it a “polar” molecule
• There is an uneven distribution of electron
density in the molecule
Hydrogen bond:
•Electrostatic attraction
between partial positive charge
near hydrogen atoms and
partial negative charge near
oxygen atom
•Weak bonds
•Non-covalent bonds
•Effective solvent
https://www.youtube.com/watch?v=PVL24HAesnc
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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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“Like dissolves like”
–Polar dissolves in polar and ionic
Ex. Salt and Water, sugar and water
–Non-polar dissolves in non-polar
Ex. oil and soap
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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
• When two liquids
completely mix they
do not mix they are
are said to be
said to be
miscible.
immiscible.
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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.
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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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
(acetic acid /
ethanoic acid)
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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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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Solubility Curves
1. What is the solubility of KNO3 at 40°C? ____________
2. What is the solubility of NaNO3 at 60°C? ____________
3. At what temperature can 45 grams of HCl be dissolved
in 100 grams of water? ____________
4. At what temperature can KNO3 and NaNO3 have the
same solubility? ____________
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Solubility Curves
65-66 grams
1. What is the solubility of KNO3 at 40°C? ____________
125 grams
2. What is the solubility of NaNO3 at 60°C? ____________
3. At what temperature can 45 grams of HCl be dissolved
90°C
in 100 grams of water? ____________
4. At what temperature can KNO3 and NaNO3 have the
67-68°C
same solubility? ____________
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Supersaturated
Sodium Acetate
• One application
of a
supersaturated
solution is the
sodium acetate
“heat pack.”