Primary 2 Length, Mass and Volume
Measure with a ruler, read a weighing-machine dial and read a measuring beaker. Switch examples, then reveal each reading step.
Measure length
Length tells us how long something is. Use centimetres (cm) for a pencil and metres (m) for longer things such as a room. 100 cm = 1 m. Line up the ends with ruler marks and count the centimetre spaces between them.
How long is the object?
Parent prompt: “Where does the object start? Where does it end? How many centimetre spaces are between those marks?” For a longer object, discuss when metres are a more useful unit.
Common mistake: Reading only the right-end number when the object does not start at 0. From 2 cm to 7 cm is 5 cm, not 7 cm.
Measure mass
Mass tells us how heavy something is. Put the object on the weighing machine, check whether the dial uses g or kg, then follow the needle to its mark.
What does the weighing machine show?
Parent prompt: “What unit is on this dial? Where does the needle point? Is this amount sensible for the object?”
Common mistake: Saying the correct number with the wrong unit. An apple shown at 200 g is not 200 kg.
Measure volume
Volume tells us how much liquid is in a container. Read the beaker at eye level. Follow the lowest point of the curved water surface to the scale, then include the unit mL.
How much water is in the beaker?
Parent prompt: “Which two numbered marks surround the water? What does the small mark between them mean? Where is the lowest point of the water curve?”
Common mistake: Reading the higher water line at the glass wall. Use the lowest point of the curve where it meets the scale.