Hold a magnet just above a steel paperclip so the class sees it jump, then hold the same magnet above a plastic bottle lid so nothing happens. Keep the hook light: one surprise, one question. Do not hand out trays or name the fair-test variables yet.

Key question: Why does the paperclip move when the plastic does not?

Have the full magnet trays ready off to the side for the next step (each tray already holds the full kit for both practicals). Remind yourself: magnets stay away from phones, tablets, bank cards and the interactive whiteboard remote.

Project only the short board text. Save magnet and magnet strength for the strength test in step 5; use the full table below for yourself when you explain and when you correct misconceptions.

Misconception to head off: children often say "all metals are magnetic" because many kitchen tools look metallic and stick. Aluminium and copper (as wire or pure copper) do not stick. Euro 1c, 2c and 5c coins look copper-coloured but are copper-plated steel and will stick — useful as a mystery object later, not as the non-magnetic metal exemplar. Another common idea is that bigger magnets are always stronger — size helps sometimes, but the material and type matter too, which is why we measure.

Nature of STEM: physicists investigate forces we cannot always see. A magnet's pull is a force at a distance. Measuring fairly is how we turn "this one feels stronger" into evidence.

Worked model (say this cycle aloud before groups test): I wonder whether this aluminium foil will stick. I predict it will not, because not every shiny metal is magnetic. I test by bringing the magnet close without touching. I observed that the foil did not move. I think aluminium is non-magnetic.

Before the lesson

• Print the Investigation Journal pages.
• Prepare one full tray per group for the whole lesson: 2 magnets that are expected to differ in strength (different size, type or known pull — e.g. a bar magnet and a weaker fridge magnet), sticky labels or coloured sticky dots marked A and B (and C if you have a third), about 20 steel paperclips, and a mixed set of test objects (steel paperclip, steel nail or screw, aluminium foil square, plastic bottle lid, wooden lolly stick or pencil, rubber eraser, short length of copper wire, small piece of card).
• Optional: two labelled sorting mats or two clear desk spaces marked Magnetic / Non-magnetic with sticky notes.
• Do not use euro coins as the non-magnetic metal exemplar: 1c, 2c and 5c are copper-plated steel and stick; €1 and €2 also contain magnetic metals. Copper wire (or a pure-copper offcut) is the reliable non-magnetic metal. Euro small coins make a good later mystery object if you want one.
• Prefer iron nail or steel screw as the sure magnetic metal. If you include a key, label it "mystery key" and sort by what the magnet does, not by the name (many keys are brass or mixed alloys).

How to run it

Hand out one magnet per group for this sort (leave Magnet B labelled on the tray for the strength test). Groups test one object at a time. Rule: bring the magnet close; do not scrape objects hard along the magnet. As they sort, prompt them to jot each material on the Investigation Journal page (name + magnetic or non-magnetic). Circulate and ask: What did you observe? Was that what you predicted?

After the tray sort, do a 30-second whole-class check on something already in the room: the steel leg of a classroom chair, a magnetic whiteboard rubber, or a metal school-gate latch if you can see one from the window. Ask: magnetic or not — and test if safe to do so.

Look-fors: pupils test before they sort; they do not guess from colour alone; they notice that some "metal-looking" items are non-magnetic; Investigation Journal page rows are begun, not left blank for later.

Differentiation: less confident groups get a shorter set of 6 clear items. Confident groups add a mystery object (e.g. a stainless-steel spoon, which may be weakly magnetic or not, or a euro 1c coin) and justify their pile with evidence.

Safety: keep magnets away from phones, tablets, bank cards and pacemakers if any adult present uses one. Paperclips are small: count them back into the tray.

Drive the sorting-tree interactive in explore mode on the IWB. Two groups appear: magnetic and non-magnetic. The yes/no guide question is: Does the magnet pull it?

Invite different pairs to decide each card. Fold the watching class in: Do you agree? What did your tray show?

Answer key for you:

• Magnetic: paperclip, steel nail
• Non-magnetic: aluminium foil, plastic lid, wooden stick, rubber eraser, copper wire, card

Non-magnetic metals in this set are aluminium foil and copper wire only. If a group tested a euro coin and it stuck, that is correct science: many euro coins are steel underneath a copper-coloured coat. Treat that as useful talk, not an error against the board key.

If a group's real steel item behaved oddly (some stainless steel is only weakly magnetic), treat that as useful science talk: the test is what the magnet did, not the name on the object.

After the sort, pupils finish any remaining Investigation Journal page rows if they have not already.

Time-tight path (use this if the clock is against you)

Two magnets only, paperclip chain only, three trials each, ordered middle value — skip a third magnet, skip polishing sentences until the journal check, and do not start through-paper. Protect the fair-test objective: change one thing, measure one thing, three recorded trials, ordered middle value.

Hand out the second magnet (30 seconds)

Each tray already has Magnets A and B labelled (sticky dots or labels). If a group only used Magnet A in the sort, point them to Magnet B now. Magnets in a pair must be expected to differ (size, type or known strength). Matched identical fridge magnets will not give a useful comparison — swap one if needed.

Default measure: paperclip chain

The board shows the chain method only. That is what groups run. Reveal the board in paced chunks as you model: (1) question and fair-test rules, (2) chain method during the demo, (3) write-each-trial and middle-value rule as trials start. Spoken model covers prediction before groups begin.

Through-paper fallback only

Use through-paper only when a second different magnet is unavailable (one magnet, change the number of paper sheets). Do not offer groups a free choice of measure on the board — that path stalls without a shared procedure.

Through-paper procedure (teacher-directed fallback):

1. Place the paperclip on the desk and hold the magnet above it so it just pulls.
2. Slide one plain paper sheet between magnet and paperclip.
3. Add sheets one by one, keeping the magnet the same distance and angle each time.
4. Stop when the paperclip no longer pulls up to the magnet.
5. Count the sheets that were still between them when the pull last worked (or the last successful sheet count — agree one rule and stick to it).
6. Three trials; order the counts; take the middle value.

Agree the fair test together first (2–3 minutes)

Model one full chain cycle at the front before groups start.

Magnet strength (say this): how strongly a magnet pulls; we compare it with a fair method and careful measuring.

Worked model: I wonder which of these two magnets is stronger. I predict Magnet A will hold more paperclips because it pulled harder on the desk. I test by hanging paperclips one by one from the same end until the chain falls, and I count how many stayed on. I keep the paperclips and the starting method the same. I write each trial on the Investigation Journal page as I go. My three trials for Magnet A were 5, 8 and 6. I put them in order: 5, 6, 8. The middle value is 6. I think Magnet A is stronger in this test if its middle value is higher than Magnet B's.

Middle-value rule (critical — say it every time): write the three trial counts, put them in order from smallest to largest, then take the middle number. Do not pick the middle trial as written on the page. (If the class already uses averages confidently, average is fine instead.)

Model a set where order matters: trials 5, 8, 6 → ordered 5, 6, 8 → middle value 6 (not 8).

Method pupils use (chain):

• Touch the first paperclip to one pole of the magnet so it hangs.
• Add paperclips one at a time to the bottom of the chain.
• Stop when the next paperclip will not hold or the chain drops.
• Count only the paperclips that stayed hanging.
• Record the number on the Investigation Journal page immediately.
• Repeat three times per magnet. Order the three counts; use the middle value (or the average).

What we change: the magnet. What we measure: number of paperclips in the hanging chain. What we keep the same: paperclip type/size, which end of the magnet we use, how gently we add each clip, counting rule.

Agency: where more than two labelled magnets are on offer, groups may choose which two to compare. Fairness rules stay teacher-secured: one measure (chain), same method every trial, three trials, middle value from ordered counts. Confident groups who finish early may try a third magnet or (if you model it) a quick through-paper check on the stronger magnet only.

Safety: magnets away from devices; watch fingers if two strong magnets snap together; paperclips off the floor promptly.