Measuring mass with a balance — Physical education, 7–10 years
A balance lets us compare how much matter objects have, even when their sizes look different.
Idea
Mass tells us how much matter is in something. A balance compares an object with known masses, so we can find a number in grams or kilograms. A large object is not always more massive: a small stone can be heavier than a big sponge.
Why
People needed a fair way to trade flour, fruit and metal instead of guessing by eye. A balance gives the same answer when the same masses are compared, even in different places. That makes recipes, parcels and buying things more reliable.
Worked example
A balance has a toy on one side and weights on the other. Two 100 g weights and one 50 g weight make both sides level. Add them: 100 + 100 + 50 = 250 g, so the toy’s mass is 250 g. The balance works because equal masses balance each other.
Common trap
It is easy to think the biggest-looking object must have the greatest mass. That guess is reasonable because our eyes often link size with heaviness. But empty cardboard can be huge and light, while a compact metal ball can be small and massive; only measuring settles it.
In the world
Bakers measure flour so each loaf gets the right amount. Shops measure fruit and parcels so people pay for the amount they receive. Scientists also measure mass when they compare samples, make medicines or plan how much material a machine can carry.
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