Science at key stage 3    (Year 8)

• Elicit pupils' ideas about magnets from their key stage 2 work about magnets, what they can do and where they are used. This can lead to the compilation of a class list of the types and uses of magnets, which will be added to as the unit progresses.

• Offer groups of pupils two magnets and a bar of steel of similar appearance. Challenge them to work out which one is not a magnet.
• Ask each group to describe and explain what they did and encourage other pupils to ask questions of them.

• Ask pupils to recall whether magnetism will act through any materials, using evidence they have from everyday life, e g fridge magnets, games such as magnetic football.
• Ask pupils to devise a test to see which materials allow magnetism to act through them, eg when a thread is attached to paper clip and taped to a bench, the paper clip will 'hover' below a magnet and fall when a sheet of magnetic material is inserted between it and the magnet. Ask pupils to suggest what the materials have in common to prevent the magnet working.

• Establish that those materials which shield magnetism can be made into magnets, eg pupils make 'soft' iron nails into magnets using the stroking technique and test the magnet's effectiveness. This could include a competitive aspect with a prize for the strongest magnet. Pupils could discuss and agree how the magnets' strength is to be tested, eg number of paper clips picked up, numbers of trials to be carried out.

• Elicit pupils' ideas about the Earth's magnetic field. Draw on their experience of a compass for direction finding. Elicit the idea that the Earth acts like a magnet. Explain that the polarities of the Earth's magnetic poles are reversed relative to the geographic poles, as a consequence of the 'opposite poles attract' rule.

• Ask different groups to devise and test various suspension techniques, eg on a thread, by floating, for allowing a freely suspended magnet to line up north-south. Discuss how well it works and when it could be used.

• Demonstrate the toy which allows you to add hair to a face by moving iron filings using a magnet. Invite suggestions as to how it works.
• Use a magnet on the overhead projector (OHP), covered with a piece of perspex, to demonstrate the magnetic field lines around a single magnet, and also between magnets with like and unlike poles facing. Explain or show, eg using a 'Magnaprobe', that the field exists in three dimensions.

• Elicit pupils' ideas about what would happen if you put a magnetic compass near a magnet and at various positions around the magnet. Invite them to generate a diagram which predicts where the compass needle will point at each position around the magnet.
• Ask pupils to test their ideas by plotting the field direction with correctly magnetised compasses and to decide how far their predictions are supported.

• Bring together pupils' ideas about magnets and magnetism by asking them to construct a concept map, using the terms encountered, eg magnet, magnetic field, field lines, north seeking, south seeking, attract, repel, Earth, and respond to a series of written or oral questions.

• Show pupils examples of solenoid coils acting as electromagnets, eg bell, buzzer, relay, etc. Ask them to make a coil, eg from insulated wire around a wooden dowel, and connect it to a low-voltage power supply and observe effects.
• Ask pupils to plan how to investigate the factors that affect the strength of an electromagnet. They could use iron cores or soft iron nails. Remind them of their investigation into the strength of the magnets they made. Discuss the best way of obtaining and presenting results so that conclusions can be drawn. Ask them to consider the limitations in their findings, eg range and precision of results, and to suggest improvements by comparing their methods with those of others.

• Provide pupils with access to a range of resources on electromagnets, eg models, devices and CD-ROMs, and ask them to report on how one application works, eg orally or using diagrams.

• Use an OHP and/or compass to demonstrate that an electromagnet has a magnetic field pattern similar to permanent bar magnets. Ask pupils to predict whether there is still a magnetic field when the iron core (the only magnetic material present) is withdrawn. Demonstrate and ask pupils to use their knowledge of magnetic materials to explain why the electromagnet's strength is far weaker without the core than with the core present. Relate this to pupils' findings in their investigation.

• Ask pupils to construct a series of 'key facts' cards based on information about the types of magnets and their uses that they have compiled during this unit.