I. Homogeneous matter is the same composition
throughout the sample
A.
Pure substances - consistent composition from sample to sample: elements and compounds
the
sample; the composition can vary from
sample to sample; it can be separated
by physical means like evaporation but the particles are too small to be
separated by filtration
C.
Soluble capable of dissolving
II. Solutions - made of two parts
A.
Solvent - the dissolving substance, usually occurs in the greater
abundance in the solution
1. Solute
- solute: energy is required to
overcome attraction forces and separate particles
2. Solvent
- solvent: energy is required to
overcome attraction forces and separate particles
3. Solute
- solvent: energy can be absorbed or
released when new attraction forces are formed
III. Types of Solutions each state of matter
can be dissolved in each of the states of matter - see
TABLE
13-1
IV. Suspensions large particles that settle out upon standing
V. Colloids - mixture composed of two phases
B. Properties - See TABLE 13-3
1. show
the Tyndall effect (the ability to make light visible by scattering it); suspensions will (but there are not
transparent), solutions won't
2.
will pass through a filter unchanged;
suspensions won't, solutions will
3.
will not settle out upon sitting;
suspensions will, solutions won't
4.
will not affect colligative properties;
suspensions wont, solutions will
5.
shows Brownian motion - ultramicroscopic particles in continuous motion
6.
good adsorbents - solid and liquid surfaces tend to attract and hold
substances
7.
shows electrophoresis - migration of charged
particles in an electric field
VI. Water is the most common solvent - called
the "universal" solvent
VII. Water as a solvent - water is polar
A.
Ionic solid compounds - electrolytes
1.
water will be attracted to and attract the ions that are in the solid
phase
2. the
water pulls the ions apart (called dissociation) and into solution; each ion is pulled away
from
its neighbors
3. the
water molecules surround each ion, called hydration, if the solvent is other than water,
this
surrounding is called solvation
4. the number of moles of particles present in
the solution is greater than the number of moles of
formula units in the solid because the ions in
the solid are pulled apart; each ion in
solution acts independently
B.
Polar solid molecules - nonelectrolytes
1. water
will be attracted to and attract other polar molecules that are in the solid
phase or liquid phase
2. the
water pulls the molecules apart and into solution; each molecule stays intact, it is merely pulled away from its
neighbors
3. the
water molecules surround each solute molecule, called hydration, if the solvent is other than water, this
surrounding is called solvation
4. the
number of moles of particles present in the solution is the number of moles of
molecules in the solid; 1 mole of solid
sugar = 1 mole of wet sugar in
solution
C.
Nonpolar solid molecules: does
not dissolve nonpolar molecule
VIII. "Like dissolves like": polar dissolves polar and ionic (ionic acts
like polar); nonpolar dissolves nonpolar
XIV.
Nonpolar solutes dissolve in nonpolar solvents
by random dispersion forces - the random
movement
of particles makes some leave the solid solute and become solvated
X. Liquid substances that are mutually soluble
in each other in all proportions are called completely
miscible; if soluble to some extent in low proportions
called partially miscible; if they do not
dissolve in each other in any appreciable amounts called immiscible
XI. Factors affecting the rate of dissolution
A. Surface area of the solute exposed: increase in surface area increase the rate
B. Agitating a solution removes solvated
particles and brings fresh solvent into contact with the
solute
C.
Heating a
solution - kinetic energy of the solute and solvent: increase in kinetic energy usually
increase the rate
XII. Solubility
equal
to the number of particles leaving the solution and returning to the solid
phase; the forward rate equals the
reverse rate - the rate of dissolution equals the rate of crystallization
B.
Temperature dependent
1. the
amount of solute that can be dissolved in a solvent at a given temperature is
called
solubility
2. solubility
curve - solubility verses temperature graph, shows how much solute can be
dissolved at different temperatures
3. solubility
of a substance is the specific amount of solute needed to form a saturated
solution in a specific amount of solvent at a specific temperature
C. At solution equilibrium the solution is called saturated, it is holding all the solute it can hold at
that temperature
1.
if the solution is holding less solute than it can at that temperature,
it is called unsaturated
2. if
the solution is holding more solute than it can at that temperature, it is
called
supersaturated; the only way to get a supersaturated
solution is to heat it up and slowly let it cool down
1. Pressure
affects the solubility of a gas:
Henry's law - the solubility of
a gas in a liquid is directly proportional to the partial pressure of that gas
on the surface of the liquid; this
means that more gas can be dissolved at a high pressure than a low
pressure; effervescence
2. Kinetic
energy of the solute and solvent:
increase in kinetic energy usually increase the
solubility
3. Heat
of solution the net amount of energy absorbed or released when a specific
amount of
solute
dissolves in a solvent
a. Endothermic
when the sum of forces 1 & 2 are greater than force 3 = positive number
b. Exothermic
when the sum of forces 1 & 2 are less than force 3 = negative number
XI. Solution concentrations measure of the
amount of solute in a given amount of solvent or solution
A.
Molarity - M: the number of
moles of solute per Liter of solution
B.
Molality - m: the number of
moles of solute per kilogram of solvent
C. Mole fraction - c: the number of moles of solute per mole of
total solution, or the number of
moles
of solvent per total moles of solution,
the sum of the mole fractions should be equal to 1