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11 Chemistry
Classification of Matter
1
Introduction: In class we saw that chemistry is the study of matter (anything that has mass and occupies space).
Matter is either:
1. Pure substance is matter that has a uniform (same throughout) and definite (constant) composition, one
kind of matter present. A pure substance is Homogeneous matter - has uniform and definite composition.
Example: a glass of pure water – same throughout H2O and has the definite composition – always H2O –
two H for one O.
OR
2. Mixture a physical blend of two or more substances. Example: salt and pepper or salt dissolved in water.
A mixture is matter that does not have definite composition, one mixture of salt and water does not have
the same composition as another mixture of salt and water. The two solutions have differing amounts of
salt .Example: solution one has 5 grams salt in a litre of water and solution two contains 15 grams of salt
in a litre of water.
Pure substances are either:
1. Element - matter that contains one kind of atom (is the simplest form of matter). Example: hydrogen gas
OR
2. Compound contains two or more different kinds of atoms bonded together and can be separated into
simpler substances (elements). Example: Sodium chloride (table salt)
A phase has uniform composition and properties. There are 4 phases solid, liquid, gas and aqueous (dissolved in
water).
Mixtures are either:
1. Heterogeneous is not uniform in composition. Example: salt and pepper mixed together; there are two
phases visible – solid salt and solid pepper.
Heterogeneous mixtures – at least two phases present.
Emulsion liquid mixed with a liquid ex: salad dressing separates
Suspension – solid and liquid ex: Maalox separates.
Colloid – 2 phases don’t separate ex: milk particles are too small for gravity
OR
2. Homogeneous is completely uniform composition. Example: a salt solution only one phase visible.
A solution is a homogeneous mixture. A solution contains a solvent that is the dispersing medium and a solute
that is the substance that is dissolving. A saturated solution – the solvent cannot dissolve any more solute.
Characteristics that help you describe and identify matter are called properties. Properties may be physical or
chemical. A physical property is a quality or condition of a substance that can be observed or measured without
changing the substance’s composition. A Physical change will alter a substance without changing its
composition. A change in state is an example of a physical change.
A chemical property is the ability of a substance to undergo chemical reactions to form new substances.
A chemical change alters the composition of matter. A chemical change occurs when one or more substances
are transformed into new substances (new composition).
11 Chemistry
Classification of Matter
2
Lab Activity
In this lab activity you will go through a circuit of 8 stations. At each station you will observe the physical
properties of the matter at that station. (Describe the visible properties of the matter and waft to describe the
odour.)
Based on these observations classify each sample (1 to 8) of matter as heterogeneous or homogeneous. State your
evidence used to classify each sample of matter.
Once you have each sample of matter classified as heterogeneous or homogeneous, try to classify each sample of
matter as a mixture or a pure substance. State your evidence used to classify each sample of matter.
What tests or procedures can we perform to check your classification as mixture or pure substance?
As a class we will perform the suggested procedure to check your classification work.
Questions
1. A student wrote “All homogeneous matter can be classified as pure substances.” Do you agree? Explain
why or why not.
2. A student wrote “Sometimes a pure substance can be classified as heterogeneous matter.” Do you agree?
Explain why or why not.
3. Explain why mixtures do not have definite composition but can have uniform composition.