Bigger is not always heavier
Distinguish visible size from weight and compare using identical weights.
Start with the activity ↓Which is heavier: a large empty box or a small stone?
Do not decide weight from size alone. Observe which pan goes down, then balance it with identical weights.
A large empty box may need two hands to hold while a small stone fits in one. Yet the stone can be heavier. Visible size and weight are different properties.
Imagine a balance with equal-length arms. First check that it is level when empty. The heavier side goes down. When balanced, the weights being compared are equal.
Leave the object in place and add identical weights to the other pan. Count how many balance it. You can describe its weight in units of those weights.
If the weights differ, their count alone is insufficient. This is like needing equal rods for length. On everyday scales, g and kg are unit labels that must be read along with the number.
Listen one paragraph at a time
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Now check it yourself
Try the large empty box and the small stone. Add or remove identical weights to balance each, then reveal the result.
Large empty box · Identical weights: 0
The object side is heavier.
Use a working balance and identical weights in the same location. These objects are examples for this activity, not claims about all boxes or stones.
Try it away from the screen
Use safe, light toys rather than heavy or fragile objects. Judging by hand is an estimate and can differ from a balance measurement.
Can you explain another example?
Check your idea 1
Check your idea 2
Can you explain it in a new setting?
Give an example showing why bigger and heavier are different.
Speak, point or draw on paper. Check whether your own explanation includes these ideas.
Continue reading, or pause here
Next, think about how much a container can hold.