Chapter 3 A property matter
Worksheet 3.2 What features of particles give matter different
properties?
To be able to understand the properties of many different materials we need to be able to visualise their
structure. As atoms and molecules are extremely small we often create models with familiar objects to help
with the visualisation process.
Making models of metals
Collect a small, empty cardboard box or metal tray. Fill it with ping pong balls or marbles. Now pour a layer of
sand over the marbles. This is your model of a metal. The marbles represent metal ions. The sand
represents the ‘sea’ of delocalised electrons. Notice how the sea is free to flow and slide over the metal
ions.
The table below explains some properties of metals in terms of this structure.
Property
Explanation
Metals are shiny
The mobile electrons in the ‘sea’ reflect most of the light
Metals conduct electricity
The mobile electrons transfer the current (a flow of electrons)
through the metal
Metals are ductile
The marbles and the sand can be easily accommodated in a
much narrower tray, showing that the metal can be easily
shaped into a wire
Two other properties of metals are that they are malleable and good conductors of heat.
1
Use your model to help you to explain these properties.
Many metals are mixed with other metals to improve their properties. The mixtures of metals are called alloys.
Brass, for example, is an alloy of copper and zinc.
2
How could you modify your model of a metal to represent an alloy?
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3
Do you think the model that you have created is useful for demonstrating the structure of a metal lattice?
What are the limitations of the model?
4
Can you think of a different way of making a model of a metal – perhaps using different materials?
Using models to explain what happens when atoms of non-metals meet: Jelly jube molecules
For this activity you will need a packet of jelly jubes or fruit pastilles and a packet of toothpicks.
Sort the jelly jubes into different colours and sizes.
Create a table like the one below to identify the atom represented by each jelly jube.
Description of jelly jube
Atom represented
Symbol
Small, red
oxygen
O
Large black
carbon
C
small white
hydrogen
H
Small yellow
sulfur
S
Large green
Chlorine
Cl
Jelly jube molecules (a group of two or more atoms held together by bonds) are made up of jube atoms linked
by toothpicks that represent bonds (forces that link atoms together).
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5
Use the jubes and the toothpicks to make models of the molecules listed in the table below and then draw
a diagram to show how the atoms are arranged.
Molecule
Chemical
formula
Hydrogen gas
H2
Sketch of the model
Shell diagram
O2
Oxygen gas
Water
H2O
Hydrogen sulfide
H2S
Methane
CH4
Carbon Dioxide
CO2
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You may find that there are several different ways that you could create the molecule.
Work through the activity Shapes of Simple Molecules Part 1 to learn about how atoms are arranged.
A covalent bond is a strong bond between two non-metal atoms. It consists of a shared pair of electrons. A
covalent bond can be represented by a straight line or dot-and-cross diagram. Use this website to learn
more about covalent bonds:
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/atomic/covalentrev1.shtml
Try the Test Bite at the end of the section on covalent bonding.
6
Why does an oxygen molecule contain a double bond?
7
How many bonds can a nitrogen atom make?
What are the properties of molecular substances?
Simple molecular substances.
Many common substances consist of small molecules which are held together by covalent bonds. The bonds
which hold the atoms in the molecules are strong but the bonds between molecules are weak. The
substances melt and boil at low temperatures. Many are gases or liquids at room temperature.
Examples are oxygen, methane, carbon dioxide, sulphur, nitrogen
Giant molecules
Some substances are continuous structures of atoms that are covalently linked together. Diamond and graphite
are examples of these. Both of these substances contain only carbon atoms but the atoms are arranged
differently so the substances behave quite differently.
Use the jelly jubes and toothpicks to make a model of the structure of diamond, and one of the structure of
graphite. You will need to have a lot of jubes the same colour to represent the carbon atoms.
More information on diamond and graphite can be found at this website:
http://www.dynamicscience.com.au/tester/solutions/chemistry/bonding/UntitledFrameset-2.html
Choose ‘Covalent-3D-network lattice diamond from the left hand menu.
8
Do the jelly jube models help you to understand how atoms are arranged and bonded in covalent
molecules?
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9
Name one advantage of using jelly jubes to make models in this way.
10 Name one disadvantage of using jelly jubes to make these models.
11 Carbon forms many different carbon compounds. How many electrons does a carbon atom need to have a
full valence shell?
12 Draw electron dot diagrams to show how the carbon atoms are sharing electrons in the diamond structure.
Compare this with the arrangements in the graphite structure.
13 Watch the animation at this site to see the process of diamond sublimation:
http://www.dynamicscience.com.au/tester/solutions/chemistry/bonding/bonding10c.htm
Why does it require such a high temperature for this to happen?
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14 Read the information about of the substances listed in the table and decide which one is a metal, which
one is an ionic compound and which one is a covalent compound. Give reasons for your answer.
Substance
Description of
substance at
room temperature
Conducts
electricity as
a solid?
Dissolves in
water?
Melting
point
X
Yellow solid
No
Yes
119
Y
Silvery solid
Yes
No
98
Z
White crystals
No
Yes
772
(°C)
15 Match the following words with their meanings:
Word or phrase
Meaning
covalent
Made up of ions, which are charged particles
metallic bonding
A mixture of two or more metals
conductivity
Able to move around
ionic
An array of positive metal ions in a sea of electrons
valence electrons
Covalent bonds between the atoms extend in all directions.
alloy
The ability of a substance to conduct electricity
property
A very large molecule consisting of many smaller structural units
linked together.
molecule
Outermost electrons of an atom
network
A characteristic of a substance
mobile
A group of at least two atoms in a definite arrangement held together
by very strong (covalent) chemical bonds.
macromolecule
Shared between
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