Put the copybooks on the scale before pupils settle so the reading is already showing. Take three hands-up answers on the heaviest object — don't confirm yet, the demo settles it.

Before the Lesson — physical kit needed: a real kitchen scale for the front demo; one kitchen or postal scale per small group (or run rotation stations if you only have one); the four demo items (a Maths book ≈ 240 g, the class register ≈ 420 g, a 2 kg bag of flour, a feather ≈ 1 g); five real objects for the circulating challenge (lunchbox, pencil case, glue-stick tub, a stapler, a full water bottle).

Weigh each object in turn and read the mass aloud. This is a real demonstration at the front, not a screen interactive — hold each object up first, then set it on the pan.

• Maths book — settle on about 240 g; say it in grams.
• Register — about 420 g; ask "heavier or lighter than the book?" before revealing.
• Flour — this is the switch to kilograms; say "2 kilograms, and that's the same as 2,000 grams because 1,000 grams make 1 kilogram" and let it land.
• Feather — the make-a-point object: even something this light still has a mass, just a tiny one.

Head off the misconception that heavy-looking means heavy — the register may surprise them. Converting between grams and kilograms with decimals is next lesson; today keep the equivalence to the whole-kilogram case the flour models.

Pupils measure at the front with a real scale — one pupil reads the dial each time, the class reads it aloud and you reconcile any disagreement as you go. This runs on the real scale, not a screen interactive.

• Lunchbox — a middling object; good for showing a prediction can be well off.
• Pencil case — lighter than most expect once emptied of guesses; grams.
• Three Maths books stacked — the deliberate build: pupils who know one book is ~240 g can reason that three should be near 720 g. Hold out for that reasoning before weighing.

Get pupils predicting and giving a reason, not just a number. Revoice a strong prediction: "so if one book is about 240 grams, three should be near 700 — let's check."

This is the practice round — real objects circulate around the room (or sit at stations) and pupils weigh each one with their group's scale. Keep the pass-on rhythm brisk; the class confirms each reading aloud at the end. If you only have one scale, run the five objects as rotation stations at the front.

• Order the objects lightest to heaviest so the numbers build: glue-stick tub → pencil case → stapler → lunchbox → full water bottle.
• The water bottle is the one likely to reach a kilogram — a good moment to ask which unit now feels right, and to remind them 1,000 g = 1 kg.

Circulate and check readings on the spot. Decimal g→kg conversion is next lesson, so today only the objects that cross 1,000 g get a kilogram value.