Solutions
Definitions
• Solution - homogeneous mixture
Solute - substance
being dissolved
Solvent - present in
greater amount
Solutions
• What the solute and the solvent are
determines
–whether a substance will dissolve.
–how much will dissolve.
• A substance dissolves faster if it is stirred or
shaken.
–The particles are made smaller.
–The temperature is increased.
Why?
Factors Affecting the Rate of Dissolution
1. temperature
2. particle size
As To , rate
As size
, rate
∆ Surface Area
3. Agitation
4. nature of solvent or solute
More mixing, rate
Solution = Solute + Solvent
• Solute - gets dissolved
• Solvent - does the dissolving
– Aqueous
– Tincture
– Amalgam
– Organic
• Polar
• Non-polar
(water)
(alcohol)
(mercury)
Dental filling
Nightmare on White Street
Chem Matters, December 1996
Classes of Solutions
aqueous solution: solvent = water
water = “the universal solvent”
amalgam: solvent = Hg
e.g., dental amalgam
tincture: solvent = alcohol
e.g., tincture of iodine (for cuts)
organic solution: solvent contains carbon
e.g., gasoline, benzene, toluene, hexane
Solution Definitions
solution: a homogeneous mixture
-- evenly mixed at the particle level
-- e.g., salt water
alloy: a solid solution of metals
-- e.g., bronze = Cu + Sn; brass = Cu + Zn
solvent: the substance that dissolves the solute
water
salt
soluble: “will dissolve in”
miscible: refers to two gases or two liquids that form
a solution; more specific than “soluble”
-- e.g., food coloring and water
Types of Solutions
Solute
Solvent
Solution
gas
gas
air (nitrogen, oxygen, argon gases)
humid air (water vapor in air)
liquid
liquid
liquid
carbonated drinks (CO2 in water)
vinegar (CH3COOH in water)
salt water (NaCl in water)
solid
solid
dental amalgam (Hg in Ag)
sterling silver (Cu in Ag)
Gaseous Solutions
gas
liquid
Liquid Solutions
gas
liquid
solid
Solid Solutions
liquid
solid
Charles H.Corwin, Introductory Chemistry 2005, page 369
An alloy is a homogeneous mixture of metals.
• Brass = Copper + Zinc
• Solid brass
• homogeneous mixture
Copper
Zinc
Solid Brass
• Brass = Copper + Zinc
• Brass plated
• heterogeneous mixture
• Only brass on outside
Copper
Zinc
Brass Plated
Hardened Steel
Steel
Iron
Carbon
Gold
Gold
Copper
Silver
24 karat gold
24/
24
atoms Au
18 karat gold
18/
24
atoms Au
14 karat gold
14/
24
atoms Au
Non-Solution Definitions
insoluble: “will NOT dissolve in”
e.g., sand and water
immiscible: refers to two gases or two liquids that will NOT form a solution
e.g., water and oil
suspension: appears uniform while being stirred, but settles over time
Solubility
Experiment 1:
Add 1 drop of red food coloring
Before
AFTER
Miscible – “mixable”
two gases or two liquids
that mix evenly
Water
Water
Water
Water
COLD
HOT
COLD
HOT
B
A
B
A
Solubility
Experiment 2:
Add oil to water and shake
AFTER
Before
Immiscible – “does not mix”
two liquids or two gases
that DO NOT MIX
Oil
Water
Water
T0 sec T30 sec
Centrifugation
• Spin sample very rapidly:
denser materials go to
bottom (outside)
• Separate blood into serum
and plasma
– Serum (clear)
– Plasma (contains red blood
cells ‘RBCs’)
AFTER
Before
Serum
Blood
RBC’s
• Check for anemia (lack of iron)
A
B
C
Blood plasma
(a solution)
White blood cells
Red blood cells
Blood
(a suspension)
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Centrifuge
Making solutions
• In order to dissolve - the solvent molecules
must come in contact with the solute.
• Stirring moves fresh solvent next to the solute.
• The solvent touches the surface of the solute.
• Smaller pieces increase the amount of
surface of the solute.
Water Molecule
Water is a POLAR molecule
d+
H2O
d-
d+
H+
H+
O2-
d-
Water molecules
“stick” together to
create surface tension
to support
light weight objects.
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Water Molecule
• What is a polar
molecule?
dHydrogen
bond
d+
H
• How does the
polarity of water
effect this
molecule?
O
H
• Hydrogen bonds occur
between two polar
molecules, or between
different polar regions
of one large macromolecule.
• One “relatively”
negative region is
attracted to a second
“relatively” positive
region.
H
O
Electronegative
atoms
H
Hydrogen
bond
N
H
H
H
Interstitial Spaces
Oil
Oil
Oil
Oil
Oil
Oil
Oil
Non-polar
"immiscible"
Layer
dissolved
solid
Water
Water
Water
Water
Water
Water
Water
Water
Polar
red food
coloring
Dissolving of solid NaCl
Polar water molecules interact with positive
and negative ions
Animation
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 468
Dissolving of solid NaCl
Na+ ClCl-
salt
Na+
Cl-
Na+
NaCl solid
(aq)
= Na+
Animation by Raymond Chang
All rights reserved.
= Cl-
Solvation
 Solvation
– the process of dissolving
solute particles are surrounded by
solvent particles
solute particles are separated and
pulled into solution
Dissolving of NaCl
H
H
O
Na+
+
+
+
+
+
-
-
hydrated ions
-
Cl-
Timberlake, Chemistry 7th Edition, page 287
+
-
Dissolving of Salt in Water
Na+
ions
Water molecules
Clions
NaCl(s) + H2O  Na+(aq) + Cl-(aq)
Dissolving of Salt in Water
Na+
ions
Water molecules
Clions
NaCl(s) + H2O  Na+(aq) + Cl-(aq)
Particle Model of a Solution
Before mixing
Fresh water
Water molecule
After mixing
Saltwater solution
Water molecule
Chloride ion, Cl-
Sodium ion, Na+