• What is in a solution
• How do we make them
• How do we dilute them
• Does pressure and temperature make a
• How do solutions mix in our body
www.ThesisScientist.comTragedy in Cameroon
• Lake Nyos
Lake in Cameroon, West Africa.
On August 22, 1986, 1,700 people
and 3,000 cattle died.
• Released carbon dioxide cloud.
CO seeps in from underground
and dissolves in lake water to
levels above normal saturation.
Though not toxic, CO is heavier
than air—the people died from
www.ThesisScientist.comTragedy in Cameroon:
A Possible Solution
• Scientists have studied Lake
Nyos and similar lakes in the
region to try and keep such a
tragedy from reoccurring.
• Currently, they are trying to
keep the CO levels in the lake
water from reaching the very
high supersaturation levels by
venting CO from the lake
bottom with pipes.
• Homogeneous mixtures.
Appears to be one substance, though really
contains multiple materials.
E.g., air and lake water.
• Heterogeneous mixtures
Appears to have two or more substances, you
can see the individual components
Chocolate chip cookies, people in a room, your
neighborhood with houses, cars and trees
• Solute is the dissolved substance.
Seems to “disappear.”
“Takes on the state” of the solvent.
• Solvent is the substance solute dissolves in.
Does not appear to change state.
• When both solute and solvent have the same
state, the solvent is the component present in the
• Solutions in which the solvent is water are called
www.ThesisScientist.comCommon Types of Solution
Solution phase phase phase Example
Air (mostly N and O )
Gaseous solutions Gas Gas
Soda (CO in H O)
Vodka (C H OH in H O)
Liquid solutions Liquid Liquid
2 5 2
Seawater (NaCl in H O)
Brass (Zn in Cu)
Solid solutions Solid Solid
• When one substance (solute) dissolves in another
(solvent) it is said to be soluble.
Salt is soluble in water.
Bromine is soluble in methylene chloride.
• When one substance does not dissolve in another it
is said to be insoluble.
Oil is insoluble in water.
• The solubility of one substance in another
depends on two factors: nature’s tendency
towards mixing and the types of
intermolecular attractive forces.
www.ThesisScientist.comWill It Dissolve?
• Chemist’s rule of thumb:
Like dissolves like
• A chemical will dissolve in a
solvent if it has a similar structure
to the solvent.
• When the solvent and solute
structures are similar, the solvent
molecules will attract the solute
particles at least as well as the
solute particles to each other.
Solvent Class feature
Water, H O Polar O-H
Ethyl alcohol, C H OH Polar O-H
Acetone, C H O Polar C=O
Toluene, C H C-C and C-H
Hexane, C H C-C and C-H
Diethyl ether, C H O C-C, C-H,
www.ThesisScientist.comWill It Dissolve in Water?
• Ions are attracted to polar solvents.
Many ionic compounds dissolve in water.
Generally, if the ions total charges 4.
• Polar molecules are attracted to polar solvents.
Table sugar, ethyl alcohol, and glucose all dissolve well in
Have either multiple OH groups or little CH.
• Nonpolar molecules are attracted to nonpolar solvents.
b-carotene (C H ) is not water soluble; it dissolves in fatty
• Many molecules have both polar and nonpolar
structures—whether they will dissolve in water depends
on the kind, number, and location of polar and nonpolar
structural features in the molecule.
www.ThesisScientist.comSalt Dissolving in Water
When materials dissolve, the solvent molecules surround the
solvent particles due to the solvent’s attractions for the solute.
This process is called solvation. Solvated ions are effectively
isolated from each other.
www.ThesisScientist.comPractice—Decide if Each of the Following
Will Be Significantly Soluble in Water.
• • p po otassiu tassium m io iod did ide, e, KI KI soluble.
• • o octan ctane, e, C C H H insoluble.
8 8 18 18
• • m meth ethan ano ol, l, CH CH OH OH soluble.
• • co cop pp per, er, Cu Cu insoluble.
• • cety cetyl l alcoh alcoho ol, l, CH CH (CH (CH ) ) CH CH OH OH insoluble.
3 3 2 2 14 14 2 2
• • iron iron(I (III II) ) su sulf lfid ide, e, Fe Fe S S insoluble.
2 2 3 3
A supersaturated solution has more dissolved solute than
the solvent can hold. When disturbed, all the solute above
the saturation level comes out of solution.
www.ThesisScientist.comAdding Solute to various Solutions
• Electrolytes are substances whose
aqueous solution is a conductor of
• In strong electrolytes, all the
electrolyte molecules are dissociated
• In nonelectrolytes, none of the
molecules are dissociated into ions.
• In weak electrolytes, a small
percentage of the molecules are
dissociated into ions.
www.ThesisScientist.comSolubility and Temperature
• The solubility of the solute in the solvent depends on the
Higher temperature = Higher solubility of solid in liquid.
Lower temperature = Higher solubility of gas in liquid.
www.ThesisScientist.comChanging Temperature =
• When a solution is saturated, it is holding
the maximum amount of solute it can at that
• If the temperature is changed, the solubility
of the solute changes.
If a solution contains 71.3 g of NH Cl in 100 g
of water at 90 C, it will be saturated.
If the temperature drops to 20 C, the saturation
level of NH Cl drops to 37.2 g.
Therefore, 24.1 g of NH Cl will precipitate.
• Formation of the crystal lattice tends to reject
• To purify a solid, chemists often make a saturated
solution of it at high temperature; when it cools,
the precipitated solid will have much less impurity