PROPERTIES OF SOLUTIONS
A. Basic Terminology
1. solution- a homogeneous mixture of two or more substances in a single phase; a “well mixed
mixture”; can be a combination of any phases of matter. Solute particles are less than 1 nm in
diameter.
2. soluble- is capable of being dissolved.
3. solvent- the dissolving medium in a solution.
4. solute- the substance dissolved in the solution.
B. Variations of Solutions
1. suspension- a mixture where solute particles are large and will settle out of the solution
unless agitated. Suspension may reflect or scatter light, is not transparent, and is
heterogeneous. Particles are generally greater than 1000 nm in diameter.
2. colloid- mixture where solute particle size is between that of solution and suspension. These
do not separate upon standing and are heterogeneous. The term colloid comes from the
Greek “kola” that means “glue”. This name was given to this variety of mixtures by Thomas
Graham in 1861. Particles range in size from 1 nm to 1000 nm.
a. distinguishing characteristics
(1) Tyndall effect- the scattering of visible light by colloidal particles
(2) Brownian motion- flashes of light or scintillations are observed under the
microscope; is a collision of the molecules of the dispersion medium with
small dispersed colloidal particles. These collisions prevent settling.
(3) coagulation- colloidal particles are charged by adsorbing ions from the
dispersing medium onto their surface.
b. types of colloids
(1) sol- solid in liquid; paint, egg whites, ink
(2) gel- solid networked throughout liquid; gelatin, toothpaste, jelly
(3) liquid emulsion- liquid in liquid; milk, mayonnaise, lotion
(4) solid emulsion- liquid in solid; butter, cheese
(5) foam- gas in liquid; whipped cream, soap suds
(6) smoke- solid in gas; industrial smoke, dust
(7) aerosol- liquid in gas; fog, disinfectants, air fresheners
(8) solid sol- solid in solid; metal alloys, cranberry glass
(9) solid foam- gas in solid; marshmallow, polystyrene foam
C. Types of Solutes
1. electrolyte- a solute that dissolves in water to produce ions in solution that can conduct
electricity.
2. nonelectrolyte- a solute that dissolves in water to produce a solution that does not conduct
electricity.
D. The Solution Process- creating a solution can be helped by three actions
1. increasing the surface area or powdering
2. stirring or agitating
3. heating the solvent
E. Levels of Solubility
1. solution equilibrium- physical state in which opposing processes of dissolution and
crystallization occurs at equal rates.
2. unsaturated solution- a solution contains less solute than a saturated solution under the same
conditions; is not concentrated, considered weak or diluted.
3. saturated solution- a solution contains the maximum amount of solute as described; is
concentrated, strong.
4. supersaturated- a solution contains more solute than a saturated solution under the same
conditions; will usually become saturated at a lower temperature.
5. solubility- amount of substance to form a saturated solution with a specific amount of solvent
at a specific temperature. Solubility charts generally have g solute/ 100 g solvent at a given
temperature.
F. Solutes and Solvents- “like dissolves like”
1. hydration- any solution process with water as the solvent.
2. miscible- liquids that dissolve freely in other liquids.
3. immiscible- liquids that are not soluble in each other.
G. Temperature and Pressure Effects
1. Can vary, and is usually dependent on phases.
2. Henry’s Law- William Henry 1803.
a. At a constant temperature, the amount of a given gas that dissolves in a given type
and volume of liquid is directly proportional to the partial pressure of that gas in
equilibrium with that liquid. That is, solubility is directly to the partial pressure of the
gas above the liquid.
b. equation:
C = kPgas
(with C as M, k as M/atm, and P as atm)
c. Henry’s Law is predictable if molecules at equilibrium, gases not at high pressure,
and if there is no chemical reaction between solute and solvent.
3. heat of solution- net amount of heat energy absorbed or released in solution process.
a. endothermic- positive heat of solution; solute mass is broken down and solvent
moves to each solute particle
b. exothermic- negative heat of solution; solute particles are attracted to the solvent