A CLASSIFICATION OF MATTER
MATTER
HETEROGENEOUS
(mixtures of
HOMOGENEOUS
(uniform composition)
non-uniform
composition, e.g.,
stones in water)
PURE SUBSTANCES
HOMOGENEOUS
MIXTURES
SOLUTIONS
e.g., sea water, air,
dental amalgams
ELEMENTS
e.g., Cu, Ag, O2
COMPOUNDS
e.g., H2O, NaCl, C12H22O11
COLLOIDS
e.g., milk, smoke,
clouds
SUSPENSIONS
e.g., muddy water,
paint
Elements and compounds are pure substances because they contain only one kind of particle
(atoms, molecules or ions), e.g., water (H2O). Since there is only one kind of particle present,
pure substances are always of uniform composition (‘homogeneous’).
Mixtures contain more than one kind of particle, e.g., air is a mixture of O2, N2 and Ar gases. In
homogeneous mixtures, such as air, all the particles are uniformly distributed.
Mixtures can usually be separated into their various components by non chemical operations
such as evaporation of a solvent, selectively dissolving one of the components (dissolving is not
a chemical reaction), filtering, extraction, etc. Components of a mixture are not chemically
combined. For example, seawater can be separated into its components by evaporating the
water, but no new substances are formed.
HOMOGENEOUS MIXTURES
Kind of Mixture
Particle Diameter
Examples
Characteristics
True Solutions
< 1 m
atoms, ions, molecules, e.g.,
sea water, air, gasoline
transparent, non filterable, won’t separate
on standing
Colloids
1 m  1 m
large molecules/ions, e.g.,
proteins, milk, butter, fog
translucent (turbid = murky), separable by
semi-permeable membranes, won’t
separate on standing
Suspensions
> 1m
large particles, e.g.,
paint, muddy water, Calomine
murky to opaque, filterable, separates on
standing
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Tyndall Effect:
Particles whose diameter is less than the wavelength of light (0.4 to 0.8 m) are invisible. Light
bends around these tiny particles. However, particles whose diameter is equal to or greater
than the wavelength of light will scatter light by reflection. A beam of light is visible in fog, dust,
or smoke because the light is scattered. This is called the Tyndall effect. Smog scatters shorter
wavelengths of light (blue, green) more than longer wavelengths (red, orange). As a result,
sunlight on the horizon (at sunset and sunrise) appears red.
Four Types of Colloids:
1. Aerosols: liquid or solid dispersed in a gas, e.g., air fresheners sprayed into the air
2. Foams: gas dispersed in liquid or solid, e.g., whipped cream, marshmallows
3. Emulsions: liquid dispersed in liquid or solid, e.g., hand lotion, milk, butter
4. Sols: solid dispersed in liquid or solid, e.g., paint, blood
Complete the following table
Example
Type of Colloid
Substance dispersed
Medium
fog, clouds
aerosol
liquid (water)
gas (air)
smoke, dust
shaving cream, soap suds
Styrofoam insulation
mayonnaise
cheese
cement (not concrete)
gels, gelatin
Semi-Permeable Membrane:
A semi-permeable membrane is a barrier through which only the smallest particles (ions and
small molecules) can pass but larger molecules cannot.
Colloids in the body are separated from solutions by semi-permeable membranes such as cell
walls and the intestinal lining. These membranes allow solution particles (O2, H2O, NaCl,
glucose, amino acids) to pass into the blood and lymph circulatory systems but not large colloid
molecules from food, e.g., starch and protein. Some foods like bran (i.e., fibers) cannot be
digested by humans and pass through the intestinal tract. The movement of solvents,
especially H2O, through a semi-permeable membrane from dilute to more concentrated solution
is called osmosis.
Types of Solutions:
1. gas in gas: air (21% O2 + 78% N2 + 1% Ar)
2. gas in liquid: carbonated beverages, air in water (fish need 4 to ppm O2 to breathe)
3. gas in solid: H2 absorbed the surface of Pt, Ni, etc. used as a hydrogenation catalyst.
4. liquid in liquid: vinegar (5% acetic acid in water)
5. solid in liquid: saline soln. (NaCl in H2O), intravenous soln. (0.9% NaCl, 5% glucose)
6. solid in solid: 14-karat gold (Ag & Cu in Au), alloy steels (Mn, C, Ni, Cr, etc. in Fe)
7. liquid in solid: dental amalgams (Hg in Cu and Ag)
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SELF-STUDY QUESTIONS FOR THE UNIT ON CLASSIFICATION OF MATTER
1. Two examples of heterogeneous mixtures are ………………………… and ……….……
2. Name the two different classes of pure substances and give an example for each:
class ……………………………………….. example ………………………………………
class ……………………………………….. example ………………………………………
3. List 3 different types of homogeneous mixtures and give an example of each
a)
…………………………………………. example ………………………………………
b) ………………………………………….. example ……………………………………….
c) ………………………………………….. example ……………………………………….
4. State the particle size range for
a) solutions ……………………….
b) colloids ………………………….
c) suspensions …………………..
5. Give the name of the kind of homogeneous mixture that exhibits the following characteristics
transparent,
separable only by semi-permeable membranes
separates on standing
translucent
filterable
won’t separate on standing
particle diameter from 1 m to 1 m
6.
Describe the Tyndall effect ………………………………………………………………………..
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
7. List 4 types of colloids and give an example of each.
a) ………………………………………. example ……………………………………….
b) ………………………………………… example …………………………………….
c) ………………………………………… example …………………………………….
d) ………………………………………… example ……………………………………….
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8. Distinguish between ‘transparent’, ‘translucent’ and ‘opaque’ substances and give an
example of each type of substance. ………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
9. Give an example of a solution that is:
a) clear but not colorless ……………………………………………………………………
b) clear and colorless ………………………………………………………………………
c) colorless but not clear ………………………………………………………………….
10. Complete the following table:
Example
Type of Colloid
Substance dispersed
Medium
fog, clouds
smoke, dust
shaving cream, soap suds
Styrofoam insulation
mayonnaise
cheese
cement (not concrete)
gels, gelatin
9. State the location of semi-permeable membranes in the human body and their importance.
……………………………………………………………………………………………………
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
10. Define osmosis ……………………………………………………………………………….
…………………………………………………………………………………………………….
11. Give an example of each type of solution listed below:
a) gas in gas:
b) gas in liquid:
c) gas in solid:
d) liquid in liquid:
e) solid in liquid:
f) solid in solid:
g) liquid in solid:
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Different components of a pure substance are chemically bonded and can only be
separated by chemical reactions and when this occurs, new substances are formed.

Hydrogen is separated from oxygen in water by electrolysis. After a separation, the pure
substance is changed to a different substance(s), e.g., H2O  H2 + O2.
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