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
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+