How Much Can You Carry?

Some objects weigh more (are heavier) and some weigh less (are lighter). We compare weights using a balance. The heavier side goes down. To compare: put one object on each side of the balance. The lower side is heavier. Examples: A brick is heavier than a feather. A pencil box is heavier than a pencil.

A balance scale has two pans. Place objects in each pan to compare. If left pan goes down: left is heavier. If pans balance (level): both are equal weight. Practice: Compare a book with an eraser. Compare 5 erasers with a book. Keep adding until the pans balance — count how many of one object equals the other.

Before kg and grams, people used: stones, seeds, hands (palm full), loads (however much one person carries). Problem: a "stone" is different in different places! So we created standard units: 1 kilogram (kg) = 1000 grams (g). A standard unit is the same everywhere in the world. A bag of rice might weigh 5 kg. A pencil weighs about 5 g.