Mass
4 Minutes
Mass and its units for kids: learn what matter is, how mass measurement evolved, and how kilograms work. An English science lesson.
- Meaning of matter and mass as the amount of matter in an object
- Evolution from barter trade to the kilogram standard in 1799
- Units like grams, tons, and historical units from Greece and Harappa
What this lesson teaches
Matter is anything that occupies space, and everything around us is made of it. Mass is a fundamental quantity that measures the amount of matter present inside an object.
How mass measurement began
Early human trade relied on bartering, where people exchanged items they owned for things they needed from others. Disagreements occurred when a trader felt their goods were heavier than the lighter goods offered in return. For instance, an exchange could cause anger until both parties compared the weight of the items by hand to ensure an equal measure. As humanity progressed, trading goods based on weight led directly to measuring mass.
Early local trade units
- In Europe, people compared the mass of items using stones, while other regions used a sack of soil.
- In ancient Greece, grain trade was based on wheat, where 12 wheat grains made one obol and 600 obols made one mina.
- A Greek mina was roughly equal to 0.5 kilograms and was also used as a unit of money.
- Traders in the Harappan civilization conducted trade using stones of different sizes as their base.
- Because every town used different objects like stones or sacks of soil, measuring mass in trade caused great confusion.
Units of mass
- Milligrams and grams measure objects with a mass smaller than a kilogram, where 1,000 milligrams equal 1 gram.
- The kilogram serves as the universal unit of mass, and 1 kilogram is equal to 1,000 grams.
- Tons are used for very heavy masses, where 1,000 kilograms equal 1 ton.
- A heavy animal such as an elephant has a mass of around 2,700 kilograms, which equals 2.7 tons.
The standard kilogram
Because different regional measuring habits caused confusion, scientists gathered in 1799 to establish a universal unit for measuring mass. They invented the kilogram and designed a platinum cylinder to define the exact mass of one kilogram. This standard reference shape was known as the kilogram of the archives. In 1889, scientists updated this cylinder and kept it safely at the International Bureau of Weights and Measures in Sèvres, Paris.