Changes In State
A Review of Matter
• Types of matter
• Pure substances
– Elements – cannot be broken down by chemical
– Compounds – two or more elements combined in
– Homogeneous – evenly mixed, uniform throughout
– Heterogeneous – unevenly mixed, varied composition
Increasing Surface Area
What is a Solution?
• Homogeneous mixture of substances in the
• A solution may be;
– A solid n solid. Ex. Zn + Cu brass (alloy)
– Gas n gas. Ex. Air.
– Liquid n liquid. Ex. alcohol + water
– And, most familiar to you, a substance, usually a
solid, dissolved in water.Ex. NaCl + water.(sea water)
Components of a Solutions
• A solute is the substance being dissolved.
• The solvent is the substance that exists in
the greater amount, into which the solute
• Ex. In sea water, salt is the solute, while
water is the solvent.
• Water’s properties make it a universal
The Secret To Waters Dissolving
Power is it’s Polarized Nature
The polar water molecules surround the solute molecules, forming H-bonds
and dipole attractions
• Solutions of a substance dissolved in
water are termed aqueous and are written
• NaCl (s) Na+ (aq) + Cl- (aq) (where
s = solid, aq = aqueous, and g = gas)
• The particles of a homogeneous aqueous
solution are very small, will not settle and
will pass through a filter.
Mixtures Can Be Separated
Properties of Mixtures
• Light will pass directly through a solution.
• The light beam will not be visible in the
body of the solution.
• Light will be scattered by the larger
particles of heterogeneous solutions.
• This is called the Tyndall Effect, after the
scientist who discovered it.
Colloids and Suspensions
Scatter Light. Solutions Do Not.
Summary of Solution Properties
• Aqueous solutions are homogeneous
• They are clear and do not disperse light.
• Can have color (ex. CuSO4 is blue).
• Particles will not settle when left standing.
• Particles pass readily through a filter.
• Ability of a substance to dissolve in
• “Like dissolves like.”
– Polar molecules dissolve in polar substances
– Non-polar (lipids, oils) dissolve in non-polar.
• All materials do not dissolve in equal
• Highly soluble materials are said to be soluble
• Materials that dissolve very little are said to be
insoluble or immiscible.
• A material dissolves because the attraction of the
solvent molecules is greater than the attractive
force holding the solute molecules together.
• Insoluble materials have a greater affinity for
their own molecules.
• These last 2 points is why oil pools together in
Temperature and Pressure
• Solubility is relative to changing temperature.
• Generally, solubility increases with increasing
• Pressure has NO EFFECT on the solubility of
solids and liquids (that compressibility thing
again) ONLY GASES.
• Gases behave oppositely, they are more soluble
at higher pressure and lower temperature
(open a warm seltzer bottle and a cold one at
the same time).
Gas Mixtures React Opposite to
Liquids in Terms of Pressure and
• We can look at a graph of solubility curves
to determine how much solute can
dissolve in a specific quantity of solvent.
• We need to know;
– Which solute
– What temperature
• See reference tables F and G.
• Guidelines for solubility (Table F)
– Table F is broken down into Ionic compounds
that are soluble. Try learning the exceptions,
there are fewer and you’ll know the rules by
• There are many Ionic compounds that are
insoluble and many exceptions (use the
• Graph of solubility curves
• Broken down into;
– X axis = Temperature in Celsius
– Y axis = amount of solute per 100g H2O.
• How to read graph
– Trace given info, grams or °C, along curve of
X and Y axis to find desired data point for
• There is an upper limit to how much solute a
given solvent can hold at a certain temperature.
• When holding the maximum amount of solute the
solution is said to be saturated.
• When a solution is saturated the addition of any
more solute will cause a precipitate to form.
• Ex. Have you ever found un-dissolved substance
on the bottom of your coffee or ice tea?
Using Table G (solubility curves)
To Predict Solubility of Substances
• Find KNO3 (potassium nitrate) in table G.
• At approximately 32°C, 100 grams H20 can hold
a maximum of ~50grams of KNO3. It is
saturated at this mass and temperature.
• If the temperature was raised to 50°C, 100g of
solvent could hold up to ~83 grams of KNO3.
• One could add an additional 33 grams of solute
to re-saturate the solution.
• If you do not add more solute, the solution
would be called unsaturated.
• This occurs when a solution is heated, saturated
and then slowly cooled, creating a new
• The solution maintains it’s homogeneous
• Supersaturated solutions are very unstable.
• Addition of a single crystalline molecule will
cause the solution to form a precipitate.
• Visual inspection: Does the solution contain un-
• Addition of more solid solute:
1. Does the solid fall to the bottom?
• Yes solution is saturated
• No solution is not saturated
2. Does a precipitate form (material comes out of
• Yes solution is supersaturated
• No return to (1)
Concentration of Solutions
• Compositions of homogeneous mixtures can
• Two terms are commonly used;
• The above terms are relative, that is, they are
not very precise and tell little about how much
solute is present.
• More precise terms are; molarity, % mass, %
volume & ppm (parts per million).
• Molarity is the number of moles of solute
per liter of solution.
M = # mol solute
• Molarity can be used as a conversion
factor to find Volume and # of mols.
M (mol/L) x V (L) = # of mol
Percent by Mass
• Mass of a certain ingredient divided by the
% Mass = Mass of part x 100
Mass of Whole
Parts Per Million
• PPM is used when very small amounts are
• Generally used to report acceptable levels
of toxins, pollutants, poisons or other
trace amounts of substances.
PPM = grams of solute x 106
grams of solution
• The process of preparing a less
concentrated solution from a more
M1 V1 = M2 V2
• Where M1 and M2 equal the old and new
• V1 and V2 equal the old and new volumes.