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Danyal Education (Contact: 9855 9224)
“A commitment to teach and nurture”
The Particulate Nature of Matter: Structure and Properties of Materials
Candidates should be able to:
a) Describe the differences between elements, compounds and mixtures
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b) Compare the structure of simple molecular substances, eg methane; iodine, with those of giant molecular
substances, eg poly(ethene); sand (silicon dioxide); diamond; graphite in order to deduce their properties
(*) (#)
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c) Compare the bonding and structures of diamond and graphite in order to deduce their properties such as
electrical conductivity, lubricating or cutting action
(candidates will not be required to draw the structures) (*) (#)
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d) Deduce the physical and chemical properties of substances from their structures and bonding and vice versa
(*) (#)
* not in combined Science syllabus
# not in N level Science syllabus
O Level Chemistry – Structure and Properties of Materials
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Danyal Education (Contact: 9855 9224)
“A commitment to teach and nurture”
What is an atom?
What is an element?
An atom is the smallest particle of an element that has
the chemical properties of that element.
An element is a pure substance that cannot be split into
2 or more simpler substances. (Eg, N, O, Mg, Ca)
What is a compound?
(A mono-atomic element is a non-metal element that
exists as atoms. Eg all noble gases like Ne, Ar)
What is a mixture?
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A compound is a pure substance that contains two or
more elements chemically combined. (Eg MgO, NaCl,
NH4NO3)
A mixture is made up of two or more substances added
together without chemical bonds being formed.
(Eg air, crude oil, sugar solution)
What is a molecule?
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A molecule is a pure substance that contains two or
more non-metal atoms that are chemically combined.
(Molecules formed by the combination of two atoms are
called di-atomic molecules, eg O2, N2, Cl2, CO.
Molecules consisting of three atoms are called triatomic molecules, eg O3, CO2.
Molecules consisting of four or more atoms are called
polyatomic molecules, eg P4, S8, NH3)
What are the differences between a mixture and a compound?
S.P.E.C.
Properties
No chemical reaction takes place when a A chemical reaction takes place when a
mixture is formed – usually there is little compound is formed – usually there is an
or no energy change.
energy change.
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Energy
Change
Mixture
Compound
The components of a mixture can be The elements in a compound can only be
separated by physical methods.
separated by chemical methods or
electricity.
The chemical properties of a mixture are The physical and chemical properties of a
the same as those of its components.
compound are different from those of the
elements in the compound.
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Separation
Composition
The components of a mixture can be The elements in a compound are always
mixed in any proportion.
combined in a fixed proportion by mass.
O Level Chemistry – Structure and Properties of Materials
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Danyal Education (Contact: 9855 9224)
“A commitment to teach and nurture”
Describe the structure of a simple molecular structure.
Give 3 examples of substances with this type of structure.
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In a simple molecular structure, the molecules exist as
simple, discrete molecules.
Within each molecule, the elements are held together by strong covalent bonds.
Between molecules, weak intermolecular forces of attraction
hold the molecules together. Eg iodine, methane, carbon dioxide, water
Describe the structure of a giant molecular structure.
Give 3 examples of substances with this type of structure.
In a giant molecular structure, a large number of atoms are joined together by strong covalent bonds, forming a
giant network of atoms. Eg diamond, graphite, silicon(IV) oxide, silicon carbide
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(Both diamond and graphite are allotropes of carbon. Allotropes are different forms of the same element.)
O Level Chemistry – Structure and Properties of Materials
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Danyal Education (Contact: 9855 9224)
“A commitment to teach and nurture”
Physical Properties of Substances with Simple Molecular Structure
Physical Property
Explaination using structure
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Low melting point and boiling point
High volatility
Weak inter-molecular forces of attraction
Very little energy is required to overcome these
forces
Usually liquids or gases at r.t.p.
No free moving ions or electrons to transfer electric
charges
Usually insoluble in water
Do not dissociate completely into its ions in water
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Do not conduct electricity in any state
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Usually soluble in organic solvents
Physical Properties of Substances with Giant Molecular Structure
Physical Property
Explanation using structure
High melting point and boiling point
Non-volatile
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Solids at r.t.p.
Strong covalent bonds between atoms
All the atoms are joined together to form a giant
network of atoms
A lot of energy is required to break these strong
covalent bonds
Do not conduct electricity in any state
(except graphite)
No free moving ions or electrons to transfer electric
charges (except for graphite, which has delocalized,
mobile electrons)
Insoluble in all solvents
Do not dissociate into its ions in all solvents
Comparing the Structures and Bonding of Diamond and Graphite
Diamond
Each carbon atom is joined to four
other carbon atoms by strong
covalent bonds in a tetrahedral
arrangement.
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Giant Molecular Structure
Properties
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Uses
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Graphite
Within each layer, each carbon atom
is joined to three other carbon atoms
by strong covalent bonds.
Layers of carbon atoms lie on top of
each other, held together by weak
forces of attraction.
Hard
Very high melting and boiling
points
Non-conductor of electricity
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Soft
Very high melting and boiling points
Conductor of electricity
As gemstones
As tips of cutting, grinding
and polishing tools
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In pencils
As a dry lubricant
As inert electrodes
O Level Chemistry – Structure and Properties of Materials
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