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Starter and plenary suggestions for Exploring Science Unit 8F
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Unit 8F – Compounds and mixtures
8Fa Let’s stick together/Coming together
Starter
Worksheet 8Fa/6 (on the website) can be used to help pupils revise the work they did on
elements and atoms in Unit 8E. The worksheet provides a set of statements which pupils are
asked to rank as true or false, and to correct any false statements. They should then decide
whether the second statement of each pair explains the first – they should use their corrected
versions for this part of the activity.
For instance:
C
D
Water is a compound.
True
Water is made up of carbon and oxygen atoms mixed together. False
Pupils should correct statement D to say that water is made up of hydrogen and oxygen
atoms joined together, then say that the corrected D explains C.
Answers:
A True
B True
B explains A
C True
D False - water is made up of hydrogen and oxygen atoms joined together
Corrected D explains C
E True
F False – there are about 100 different elements.
Corrected F does not explain E
G False – chlorine is a dangerous gas and sodium is a dangerous metal, but sodium
chloride is safe
H False – a compound usually has very different properties to the elements that make it up.
Corrected H explains corrected G
Plenary
Worksheet 8Fa/7 (on the website) provides further practice in identifying which elements are
in a particular compound based on its formula. Pupils are asked to work out the number of
different elements, and to say how many atoms of each element there are in a molecule of the
substance. Pupils could also draw diagrams to represent molecules – examples of some of
those asked for are given in the Pupil’s Book.
Pupils could work on the task individually or in groups, or the individual formulae could be
written on an OHP or the board one at a time, and the class as a whole asked to volunteer
answers.
Exploring Science 8
This material may be adapted for use in schools.
© Pearson Education 2003
Starter and plenary suggestions for Exploring Science Unit 8F
Page 2
8Fb All change/Split ends
Starter
Remind pupils of the criteria for deciding whether or not a chemical reaction has occurred
(colour change, evolution of gas, energy change) by demonstrating a few reactions. Those
suggested in Topic 7Fa Practical 1 (in Teacher's Guide 7) are suitable, and you may also
wish to include the displacement reaction between copper sulphate solution and iron as
shown in the Pupil’s Book. You could also show a kettle boiling or an ice cube melting. Ask
pupils which changes are physical changes and which are chemical reactions, and ask them
to explain how they made their decisions.
Plenary
Pupils can be asked to make a concept map to demonstrate their understanding of chemical
change, using words such as atom, element, compound, etc. Worksheet 8Fb/3 (in
Copymaster File 8) could be used to help less able pupils.
Alternatively, if Worksheet 8Fb/3 is required for homework, you could use the Odd One Out
suggestions on the Thinking Skills page in Teacher’s Guide 8 to revise the work covered in
the Unit so far. These and some additional suggestions are reproduced below, together with
some possible answers.
Compound, element, atom
atom (the others are both made from atoms), compound (the only one that has
more than one type of atom)
Iron, sulphur, iron sulphide
iron sulphide (it is the only compound), iron (it is the only one that is magnetic)
Water, steam, oxygen
water (it is the only liquid), oxygen (it is the only element)
Carbon dioxide, sulphuric acid, hydrochloric acid
carbon dioxide (it is the only gas, it is the only one that is not an acid),
hydrochloric acid (it is the only one that does not contain oxygen atoms)
8Fc All mixed up
Starter
Show pupils a range of materials and ask them to suggest which are mixtures and which are
compounds, and ask them to justify their decisions. Pupils could be asked to suggest what is
in the mixtures. This is a good point at which to introduce the fixed ratio of elements in a
compound, as opposed to the variable ratios of elements/compounds found in mixtures.
Suitable mixtures (some of which are also shown in the Pupil’s Book) include:
Sulphur and iron (a mixture of two solid elements)
Sea water (a mixture of water, sodium chloride and other compounds dissolved in the water).
Distilled water (a compound)
Exploring Science 8
This material may be adapted for use in schools.
© Pearson Education 2003
Starter and plenary suggestions for Exploring Science Unit 8F
Page 3
Sand (a compound – ensure it is clean, otherwise it can legitimately be described as a
mixture!)
Rock (a mixture of solid compounds)
Shaving foam (a mixture of a liquid compound and a gaseous compound – it is sufficient for
pupils to say that it is a mixture of a liquid and a gas)
Plastic (a compound)
Ink (a mixture of water and various pigments – all compounds)
Rusty iron (a compound)
Muddy water (a mixture of insoluble solid compounds and water – a liquid compound)
Plenary
Worksheet 8Fc/8 provides a set of cards showing elements, compounds, and mixtures of
elements and compounds. Pupils should be asked to match up the diagrams with appropriate
labels, and to justify their answers. This activity is best done in small groups, with the groups
reporting back to the class after five or ten minutes. The worksheet could also be copied onto
acetate and the cards used for a whole-class discussion.
Answers:
A
B
C
D
E
F
G
H
I
J
compound
mixture of two elements
element
mixture of two compounds
mixture of two compounds
mixture of an element and a compound
compound
mixture of two elements
mixture of an element and a compound
element
8Fd Separating it out
Starter
Give pupils copies of worksheet 8Fd/5 (on the website), and ask them to produce questions
to fit the answers given. Pupils can work in small groups before holding a short class
discussion to decide what the questions should be. This can be done orally or in writing.
Note that the answers cover work from Topics 8Fa to 8Fc.
Possible questions for the answers provided are:
1 What is a more common name for hydrogen oxide?
2 What does the 2 in the formula for hydrogen (H2) tell you?
3 What does the formula for sodium chloride (NaCl) tell you?
4 Which two elements would you find in a molecule of water?
5 What is the name for a solid that forms when two liquids are mixed?
6 What does ‘decompose’ mean in chemistry?
7 Which gas in the air exists as single atoms?
8 How is the air you breathe out different to the air that you breathe in?
Exploring Science 8
This material may be adapted for use in schools.
© Pearson Education 2003
Starter and plenary suggestions for Exploring Science Unit 8F
Page 4
Plenary
Use the following PMI suggestions as a plenary activity (see the notes on PMI activities on
page 10 of Teacher's Guide 7). Each group could be given just one statement and two
minutes to come with suggestions, then their responses could be reported back to the class
for discussion. Note that these suggestions cover work done in this topic and in topic 8Fc.
PMI suggestions:
Tap water should come with a list of minerals, as bottled water does.
The sea should be pure water.
There should be no nitrogen in the air.
No foods should be sold with artificial additives.
All drinks sold should be pure compounds.
8Fe Boiling in the freezer
Starter
As suggested in the Teacher's Guide for this topic, a good way to start the lesson is to have a
candle burning as pupils enter the room. Pupils can be asked to describe what is happening to
the wax. The main point to elicit is that the wax evaporates before it burns. The Teaching
ideas and notes for this topic suggest a couple of ways that you can demonstrate this.
Plenary
Worksheet 8Fe/4 (in Copymaster File 8) can be used to help pupils to review the contents of
the whole unit. The worksheet provides a set of statements that can apply to elements,
mixtures or compounds (or may apply to more than one category). More details of this
activity can be found in the Teaching ideas and notes for this topic.
Exploring Science 8
This material may be adapted for use in schools.
© Pearson Education 2003