Measurement is used to determine the size of things. Units are used to give a value to a measurement in a standard way.

**Length** measures distance in centimetres, metres, inches and feet.

**Mass** measures how heavy something is, and may be measured in grams, kilograms, ounces or tons.

**Capacity** measures volume, using litres, pints or gallons.

Note: Mass is not the same as weight. On the moon, you would weigh `frac(1)(6)`th of the weight as you would on earth, yet your mass is still the same. The difference between mass and weight is the effect of gravity or other force.

I pour milk from a container. Would the amount of milk in the container be shown as a length, a mass or a volume?

Liquids are not measured in lengths. It could be measured as a mass, but liquids are most normally measured as a volume.

Answer: A volume.

A satellite has landed on the moon. The moon has `frac(1)(6)` of the gravity of earth.

Could the weight of the satellite on the moon be derived from the length, the mass or the capacity of the satellite?

The weight of an object is given by the force (eg gravity) acting on its mass.

Answer: The mass of the satellite.

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