8.1 Solutions and Other Mixtures
Heterogenous Mixtures
 Does not have a fixed composition
 Each substance varies in amount
Suspension - solid/liquid mixture where particles are large and
settle out over time. (Italian salad dressing)
 Particles may be filtered out; bacteria, 1000nm
Some liquid/liquid mixtures will settle out
 Immiscible liquids completely separate; Italian
dressing
 Decanting – pouring a less dense liquid off a denser
liquid; gravy from fats
Particles in a Colloid are too small to settle out; stay suspended
 Particles are smaller than suspensions (1-1000nm)
 Pass through most filters, (latex paint)
 Particles small enough to scatter light (Tyndall Effect)
 Common foods; gelatin, egg whites, blood plasma (protein colloid)
 whipped cream and marshmallows, Fog/Smoke
 *Some immiscible liquids can form colloids
 Emulsions – liquid mixtures of two immiscible liquids
held together by a protein(in eggs) binder, Oil/vinegar
with egg white = Mayonnaise
Homogenous Mixture
 Solutions - particles are evenly dispersed
 Solute is the substance being dissolved
 Solvent is the substance doing the dissolving
 Miscible liquids mix to form solutions; vinegar and water
 Liquid solutions sometimes contain no water
 Petroleum products –gasoline, diesel, kerosene, plastics
fingernail polish remover, paint strippers
 **Other states of matter can also form solutions**
o S-L-G combinations are all possible
In Solids
In Liquids
In Gases
Solids
Metal
Alloys(first
melted then
cooled)
Italian Dressing
Smoke
Liquids
amalgam Hg +
Ag (second
metal also
melted first)
water/acetic acid
oil/vinegar (mayo)
chocolate milk
Gases
Marshmallows
Carbonated
beverage;
Whipped
Cream
Fog
Atmosphere
8.2 How Substances Dissolve
Water a Common Solvent – Universal Solvent
 Water can dissolved ionic compounds (ripping apart)
Why???
 Polar molecule- describes a molecule in which the positive
and negative charges are separated (and
those ends attract opposite charge particles)
 Dissolving depends on the force between the particles; strong
bonds, not very soluble; sugar vs salt; Silver Nitrate – too
strong to dissolve
 Water dissolves many molecular compounds (vitamins,
sugars) Hydrogen bond is important in dissolving other
polar molecular compounds
 Like dissolves Like- Polar dissolves other Polar compounds
The Dissolving Process (think Kinetic Theory)
 Solutes with a larger surface area dissolve faster
 Stirring or shaking helps solids dissolve faster
 Solids dissolve faster when the solvent is hot
 Solutes affect the physical properties of solutions
 Boiling point in will increase due to more particles absorbing the
thermal energy
 Freezing point will decrease
8.3 Solubility and Concentration
 Solubility - the ability of one substance to dissolve in another at a
given temperature and pressure
 Different substances have different solubility’s
 Due to strength of forces acting between the solute
particles and the strength of the force between the water
molecules and solute particles
How much substance is in a solution?
 General terms – Strong or weak
 Dilute – very little solute compared to amount of solvent
 Concentrated – a lot of solute compared to amount of
solvent
 More specific. Based on ability of substance to dissolve in a given
solvent
 Saturated - maximum about of solute at room temp; cannot
dissolve any more; equilibrium
 Unsaturated – able to dissolve more solute in the solvent
without separation occurring
 Supersaturated – able to “hold” more solute than normal
due to heating solvent to increase solubility
Concentrations of Solutions
 Molarity – quantitative measurement expressed as the number of
moles of solute per liter of solution
 M solution is read as “one molar” solution
Let practice – Molarity of a 1.0 L solution containing 25 grams of NaCl
 Number of moles(solute) divided by the liters of solvent
used.
Solute is NaCl = 58g/mol
(23g/mol + 35g/mol)
You have 25g of NaCl
divide by 58g/mol = .43 moles
Then divide moles of solute by liters of solvent
.43 moles / 1 liter = .43 molar solution. Easy as that!!