National 5
Elements, Compounds
and Mixtures
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1. Elements
1.1.
Organising Elements – The Periodic Table
Are all the elements in the known world the same?
Students in school are gathered together by age and subject being studied to form a class. In a
supermarket, similar foods are gathered together, e.g. fruit, cereals, meat.
When we are faced with a wide variety of things we often try to gather together those which have
something in common.
This is called classification.
Elements are the building blocks of all substances in the world just as bricks are the building blocks
of houses. Just over 100 different elements are known.
There are different ways of gathering the elements together so that all the elements in the one "class"
have something in common. Modern-day chemists have classified elements by arranging them in the
Periodic Table.
Activity 1.1
Using the information above answer question 1 & 2 over the page.
Now look at samples of some of the elements also look at a suitable
Periodic Table. Complete the 3 tables over the page as you go through
the 6 stages of the activities.
1. Find some
-
shiny elements,
coloured elements.
2. Find some
-
metal elements,
non-metal elements.
3. Find some elements which are
-
solid at room temperature,
liquid at room temperature,
gas at room temperature.
4. Find some elements which are
-
naturally occurring,
made by scientists.
5. Find some elements which are
-
stored under oil.
6. Find some elements which are
-
named after a planet,
named after a scientist,
named after a place.
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Questions:
1. Approximately how many different elements are known?
2. What name is given to the modern-day arrangement of elements?
3.
Copy and complete the following tables.
Include a number of elements under each heading.
Solid
Liquid
Gas
Metal
Non-metal
Naturally occurring
Made by scientists
1.2 Chemical symbols
Why does sodium not have the symbol S?
A chemical symbol is a "shorthand" way of representing an element.
Each element has its own chemical symbol.
The ancient chemists (or alchemists) were the first to use symbols for elements in place of their names,
e.g.
Modern symbols for elements consist of one or two letters. The first letter is always a capital letter;
the second is always a small letter.
A few elements have symbols which come from the Latin name. For examples the Latin name for
sodium is natrium and for silver it is argentum.
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Activity 1.2 Elements and Symbols
Look at a suitable Periodic Table and use text book page…. to find some elements which have a
symbol

that is the first letter of its name,

that is the first two letters of its name,

that comes from its Latin name.
1.
Copy and complete the following table remembering that a capital letter is used for the
symbol.
Element
Symbol
hydrogen
C
iodine
N
sulphur
V
2.
Copy and complete the table below remembering that only the first letter of the symbol is
a capital letter.
Element
Symbol
chlorine
Mg
calcium
Sc
argon
Si
3.
What is the symbol for helium?
4.
Why is it not just H?
5.
What is the symbol for cadmium?
6.
Why is it not just C or Ca?
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7.
Copy and complete the following table.
Element
Symbol
Latin name
gold
silver
iron
sodium
potassium
Extension: Make up your own element with its own unique properties and symbol. Describe it to
your teacher when you have finished.
Families of elements – Groups in the Periodic Table
1.3
Some elements are very reactive; others are quite unreactive. Elements are arranged into ‘families’ with
similar properties called groups.
Activity 1.3 – Reactivity of Group 1 Metals
Your teacher will carry out a demonstration
to show the reactivity of group 1 metals in
water. They will also show you a short DVD(1)
about Group 7 and 8 elements.
Take a copy of Notes 1.1 and stick it into your notes after completing it.
1.
How are the alkali metals stored?
2.
Why are they stored in this way?
3.
Describe the reactions of the alkali metals with water.
4.
Describe a reaction involving chlorine.
5.
Why are the noble gases often referred to as the inert gases?
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2. Compounds and mixtures
Are you made up of compounds or a mixture of elements?
2.1
Compounds
Most of the substances which exist in the world are not pure elements - they are compounds.
A compound is made up of two or more elements which are chemically joined together. Since they
are joined together it is difficult to separate out the elements which make up the compound. Energy
must be supplied to do this.
Some elements, e.g. carbon and oxygen, are found in lots of compounds; other elements make very
few compounds.
Activity 1.4
Look at the display of substances.
Identify the substances which are
- pure elements
- compounds.
1.
What is meant by a compound?
2.
Is it easy to separate out the elements which make up a compound? Explain.
3.
Copy and complete the following table for the substances in the display.
Element
Compound
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2.2 Making and breaking compounds
a) Making magnesium oxide
A compound is very different from the elements which make it up, e.g. sugar (a white
solid) is made from carbon (a black solid) and hydrogen and oxygen (both colourless
gases).
Magnesium oxide can be made by burning magnesium in oxygen.
Activity 1.5
Safety:
DON'T LOOK DIRECTLY AT BURNING MAGNESIUM.
THE BRIGHT LIGHT COULD DAMAGE YOUR EYES.
1.
2.
Using tongs, hold a piece of magnesium
ribbon (3 cm) in a Bunsen flame until it
burns.
Remove the product from the flame and
examine it.
1. Copy and complete the following table.
Name
Appearance
Elements reacting
Compound
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(b) Breaking up copper chloride
Electricity can be used to break up copper chloride into its elements. This process
is called electrolysis.
Activity 1.6
1.
Half-fill a small beaker with water.
2.
Add a few spatulafuls of copper chloride.
Stir until it all dissolves.
3.
Gently clean the carbon electrodes
with sandpaper.
4.
Set up the apparatus shown.
5.
Identify the products at the positive
and negative electrodes.
1. What form of energy is used to break up the compound?
2. What is the process called of breaking up a compound using electricity called?
3. Copy and complete the following table.
Name
Appearance
Elements
formed
Compound
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2.3
Naming of compounds
Important Rules for Naming Compounds:
 Compounds containing only two elements have names ending in -ide, e.g.
sodium chloride contains only sodium and chlorine.
 Compounds containing more than two elements, one of which is always
oxygen, have names ending in -ate or -ite, e.g. copper sulphate contains
copper, sulphur and oxygen.
Activity 1.7
Answer questions 1 & 2 below.
Then look at compounds in the display. Using the rules above identify the elements in each of the
compounds and fill out the table in question 3.
1.
Compounds containing only two elements have what name ending?
2.
Compounds containing two or more elements, one of which is oxygen, usually
have one of what two name endings.
3.
Name the elements which can be found in the following compounds:
 Lithium fluoride
4.

Magnesium nitride

Potassium sulphate

Calcium chloride

Magnesium carbonate

Lithium sulphite

Potassium oxide

Sodium chlorate

Aluminium phosphate
Copy and complete the following table for the compounds in the display.
Compound
Element present
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2.4 Mixtures
Did you know that air is a mixture of gases! But what gases are in air?
Very few substances in nature are found on their own - they are usually mixed with other
substances.
A mixture contains two or more substances which have come together without reacting; the
properties of a mixture are the same as those of the substances in it.
Different elements are chemically joined together in a compound; the properties of a compound are
different from those of the elements which make it up.
Activity 1.8
Look at the samples of pure sulphur, pure iron.
Now you can help your teacher to demo the difference between a mixture of iron and
sulphur and a compound of iron and sulphur. A magnet can be used to demonstrate this.
1.
What is the main difference between a mixture and a compound?
2.
Draw diagrams to show this difference.
3.
Describe how to separate a mixture of iron and sulphur.
Explain.
4.
Can iron be separated from a compound of iron and sulphur using a magnet?
Explain.
5.
What is the name of the compound made by sulphur and iron?
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Activity: Filtration: Separating a solid from a Liquid
Can you think where you would use filters in your home?
This is an assessable technique.
Filtration apparatus:
Insoluble solid (residue) is trapped in the paper
Filter Paper
Filter Funnel
Beaker to collect filtrate
Retort Stand
Instructions:
1.
Collect two clean beakers, filter paper, a filter funnel and a retort stand.
2.
Set up the apparatus as set out above.
3.
Take the filter paper and fold it in half, then half again. Open it up (it should be a
cone shape). Wet the paper slightly and place it in the filter funnel.
4.
With the second beaker collect some dirty water from the trolley.
5.
Filter the dirty water.
6.
Collect a Practical Technique write up sheet and complete it.
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2.4 More Mixtures - Air
The air around us is an example of a mixture of gases.
Dry air contains approximately 78% nitrogen, 21% oxygen and small
amounts of carbon dioxide, helium, neon, argon and xenon.
Oxygen gas is produced when potassium permanganate is heated.
This can be used to find the test for oxygen.
Activity 1.9 – Testing for Oxygen
SAFETY In this experiment you MUST check with your
teacher before starting.
1.
Clamp at the mouth.
Test-tube is horizontal.
3.
Gentle heat until potassium permanganate begins to 'crackle'.
Check what happens to a glowing-splint held in the test-tube.
2. Add 2 spatulafuls of potassium
permanganate followed by a loose
plug of rocksil wool.
1.
Draw a table showing the mixture of gases in air and the percentage (%) they make up.
2.
Describe the test for oxygen.
3.
Why does the oxygen in the air not give a positive result to this test?
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2.5 More Mixtures - Solutions
(a) Solute, solvent and solution
A solution is a mixture of a solute which is dissolved in a solvent. Sea water is an example of a solution.
The salt is the solute and the solvent is the water. Together they make a sea water solution which is a
mixture. You cannot see the salt in sea water, but it can be tasted.
Activity 1.10
1.
Add about 20 cm3 of water (the solvent)
to an evaporating basin
2.
Add three spatulafuls of salt (the solute)
Stir until it all dissolves.
3.
Gently heat the solution on a tripod to
evaporate the water and recover the salt.
When a solute dissolves in a solvent to form a solution, no new substance is formed.
Solutions are therefore mixtures.
In an aqueous solution, the solvent is water. Substances which are insoluble in water may be soluble in
other solvents, e.g. turpentine is a suitable solvent for paint, acetone dissolves nail polish.
1. Is it easy to separate a solute and solvent from a solution?
2. Write a brief not on how this is done.
3. Using a Chemistry Text book find out the full definitions of solute, solvent and solution
and write them into your notes.
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(b) Dilute, concentrated and saturated
How do you turn a concentrated solution of orange juice into a dilute solution of orange juice?
Activity 1.11 – Making a Dilute, Concentrated and Saturated Solution
1. Add about 10 cm3 of water to each of five test-tubes.
2. To the first test-tube add 1 spatulaful of copper sulphate to make
a dilute solution.
3. To the second test-tube add 2 spatulafuls of copper sulphate and so on to make
successively more concentrated solutions.
Carefully shake each test-tube to dissolve as much copper sulphate as possible.
4. Observe the colours of the solutions.
Note which test-tubes contain undissolved copper sulphate (saturated solution)
5. Dilute the solutions by adding a further 10 cm 3 of water to each of
the five test-tubes. Again carefully shake each test-tube to dissolve as much copper
sulphate as possible.
6. Observe what happens to the colours of the solutions.
Note which test-tubes now contain saturated solutions.
Take a copy of Notes 1.2 and stick it into your notes after completing it.
Consolidation Activity: Elements, Compounds and Mixtutres.
1. Collect a Standard Grade Text book and read pages 3 to 7 answering
questions 1, 2 and 3 along the way.
2. Turn to page 8 in the text book and answer questions 3 to 10.
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