Download 2. Classification of matter Chemistry: Matter and

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2. Classification of matter
Chemistry: Matter and materials
Grade 10
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All the objects and substances that we see in the world are made of matter.
This matter can be classified according to whether it is a mixture or a pure substance
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DEFINITION: Mixture
A mixture is a combination of two or more substances, where these substances
are not bonded (or joined) to each other and no chemical reaction occurs
between the substances. Examples of mixtures are air (a mixture of different
gases) and cereal in milk.
The main characteristics of mixtures are:
●that the substances that make them up are not in a fixed ratio
●these substances keep their physical properties
●these substances can be separated from each other using mechanical means.
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Mixtures
Heterogeneous mixture
A heterogeneous mixture is one
that consists of two or more
substances. It is nonuniform and
the different components of the
mixture can be seen. An example
would be a mixture of cereal in
milk.
Homogeneous mixture
A homogeneous mixture is one
that is uniform, and where the
different components of the
mixture cannot be seen. An
example would be black coffee.
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DEFINITION: Pure substance
Pure substances are any material that is not a mixture. Pure substances
cannot be broken down into their component parts by ordinary chemical
means. Examples are any element, e.g. aluminium, sulphur and any
compound, e.g. iron sulphide.
Pure substances have a sharply defined (one temperature) melting or boiling point.
●Pure substances show only one substance at the end of the chromatography process.
●Pure substances cannot be broken down into their constituent parts by ordinary chemical
means.
●
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Pure substances
Compounds
Elements
A compound is a a substance made
up of two or more different elements
that are joined together in a fixed
ratio. Examples of compounds are
sodium chloride (NaCl), iron sulphide
(FeS), calcium carbonate (CaCO3)
and water (H2O).
An element is a substance that cannot
be broken down into other substances
through chemical means. All the
elements are found on the periodic
table. Each element has its own
chemical
symbol. Examples are iron (Fe), sulphur
(S), calcium (Ca), magnesium (Mg) and
fluorine (F).
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NAMING COMPOUNDS
When naming compounds and writing their chemical formula, it is important to
know
the elements that are in the compound, how many atoms of each of these elements
will combine in the compound and where the elements are in the periodic table. A
number of rules can then be followed to name the compound.
1.The compound name will always include the names of the elements that are part of
it.
2. The element on the left of the periodic table is used first when naming the
compound.
3.The symbols of the elements are used to represent the compound.
4.A compound may contain ions. You should know all the common anions and cations.
5. Prefixes and roman numerals are used to describe the ratio of elements in the
compound.
Iron + Sulpher = iron sulphide
Fe + S = FeS
Potassium + permanganate = potassium permangante
K + MnO4
= KMnO4
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ELEMENTS
Metals
Metalloids
Metals are found on the left
of the periodic table.
Metals:
●are good electrical and
thermal conductors
●have a shiny lustre
●are malleable and ductile
●have a high melting point.
●have a high density.
Are found on the
zig-zag line that
seperates the
metals and the
non-metals.
Metalloids are
semi-conductors.
Non-Metals
Non-metals are found on
the right of the periodic
table.
Non-metals:
● are poor thermal
conductors
● are good electrical
insulators
● are not malleable or
ductile.
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Electrical and thermal properties of matter
Electrical
conductors
Matter
Semi-conductors
Insulators
Thermal conductors
Matter
Insulators
An electrical conductor allows an electrical current
to pass through it. Most metals are good electrical
conductors.
Semi-conductors start conducting electricity as
their temperature rises
An electrical insulator is a non-conducting material
that does not carry any charge. Examples are
plastic, wood, cotton material and ceramic.
A thermal conductor allows heat energy to
be transferred within the material. A thermal
insulator does not allow heat energy to be
transferred within the material.
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Magnetic materials
Materials may also be magnetic or non-magnetic. Magnetism is a force that certain
kinds of objects, which are called ‘magnetic’ objects, can exert on each other without
physically touching. A magnetic object is surrounded by a magnetic ‘field’ that gets
weaker as one moves further away from the object.
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