Primary 2 · Mathematics
P2 volume
Put a tall bottle filled high beside a wide tub filled low, and ask which holds more water. The bottle usually wins. One cup of water, poured into two different glasses, shows why it should not.
- Level
- P2
- Usually taught
- Term 3
- Covers
- 1 concept
What changes at P2
In Primary 2 your child meets volume: how much liquid a container holds. It is measured in litres (ℓ), read off the marks on a measuring cylinder, or found by counting how many identical cups a container fills. Millilitres wait until P3.
The shift is that volume becomes a number you read, not a height you see. The same water can sit at very different levels in two containers of different shapes.
The sentence that costs the mark
Container A is tall and narrow. Container B is short and wide. Which container has more water?
What the working usually does
more water:higher level=Container A
Sees the water in A standing higher and reads that as more.
What the question asked
more water:more litres=Container B
Reads each scale. A has 2 ℓ and B has 5 ℓ.
"Higher means more" is true when two containers are the same shape, which is how most first examples look. So the child compares something real. It is just the wrong thing to compare once the shapes differ.
| Reading | ℓ |
|---|---|
| Level | 2 |
| Reading | ℓ |
|---|---|
| Level | 5 |
The same question, worked properly
Do not compare the water levels
A and B are different shapesA narrow container pushes the same water higher. The level only compares amounts when the containers match.
Read the litres
A: 2 ℓ, B: 5 ℓThis is the step that fails. Check what each mark is worth, then read where the water comes to on each scale. An answer read off the picture never gets this far.
Compare the numbers
5 ℓ > 2 ℓContainer B has more water, even though its water sits lower.
How can you tell it has clicked?
Set out two glasses of different shapes with water at different heights, and ask which has more. Watch where your child looks before answering.
A child who looks for the marks, or asks to pour both into the same cup, has it. A child who points at the higher water is comparing heights, and that answer is right only when the glasses match.
One thing to try tonight
Pour one cup of water into a tall glass, then pour the same water into a wide bowl, and ask each time whether there is more water now.
When "the glass has more" comes back, pour it back into the cup. Nothing was added or spilled, and seeing the same cup fill up again settles it.
What your child will meet in this topic
- Volume in ml and L
Most Singapore schools introduce this in Term 3, though schools do differ by a term either way. If your child’s school runs a different order, you can set it in the schedule on your dashboard.
What it leads to
P3 adds millilitres (1 ℓ is 1000 ml) and compound units like 2 ℓ 350 ml. Comparing still means reading numbers in one unit, never judging by the level.
In P5 and P6, volume returns as length × breadth × height, where a tank's base area decides how fast the water level rises.
The same topic in other years
It comes back each year and gets harder, so it helps to see what came before and what is coming.
More in Primary 2
Other topics in the same year, so you can see what sits either side of this one.
See how your child is doing on this topic
StudyLah marks each step separately, so you can see whether it was the setup or the arithmetic that cost the mark.