Measures
Volume and Capacity
3rd Class · 4th Class · 5th Class · 6th Class
- ✓By the end of this lesson students will be able to explain the difference between volume and capacity.
- ✓By the end of this lesson students will be able to identify and use standard units of volume (cm³) and capacity (ml, l).
- ✓By the end of this lesson students will be able to convert between millilitres (ml) and litres (l).
- ✓By the end of this lesson students will be able to calculate the volume of a cuboid.
- ✓By the end of this lesson students will be able to solve simple problems involving volume and capacity.
Key concepts
Volume is the amount of space that a 3D (three-dimensional) object takes up. Think of how much space a brick or a book fills. We measure volume in cubic units.
Capacity is the amount of liquid or substance that a container can hold. Think of how much water a bottle can hold, or how much milk a carton can hold. We measure capacity using units like millilitres and litres.
A cubic centimetre (cm³) is a unit of volume. It is the volume of a cube with sides that are each 1 centimetre long. Imagine a tiny cube, 1 cm long, 1 cm wide, and 1 cm high.
A millilitre (ml) is a small unit of capacity. It is often used for measuring small amounts of liquid, like medicine or a small drink. There are 1,000 millilitres in 1 litre.
A litre (l) is a standard unit of capacity. It is used for measuring larger amounts of liquid, like a bottle of milk or a carton of juice. One litre is equal to 1,000 millilitres.
There is an important link between volume and capacity: 1 cubic centimetre (cm³) is equal to 1 millilitre (ml). This means if a container has a volume of 100 cm³, it can hold 100 ml of liquid.
A cuboid is a 3D shape like a rectangular box. To find its volume, you multiply its length by its width by its height.
Key facts to remember
- 1Volume is the space an object takes up, measured in cubic units (e.g., cm³).
- 2Capacity is how much a container can hold, measured in liquid units (e.g., ml, l).
- 3The abbreviation for cubic centimetre is cm³.
- 4The abbreviation for millilitre is ml.
- 5The abbreviation for litre is l.
- 61 litre (l) = 1,000 millilitres (ml).
- 71 cubic centimetre (cm³) = 1 millilitre (ml).
- 8The volume of a cuboid is calculated by Length × Width × Height.
Worked examples
Example 1
Convert 3.5 litres to millilitres.
Answer
3,500 ml
Remember, when you multiply by 10, 100, or 1,000, the decimal point moves to the right.
Example 2
A rectangular lunchbox has a length of 20 cm, a width of 10 cm, and a height of 5 cm. What is its volume in cubic centimetres?
Answer
1,000 cm³
The volume tells us how much space the lunchbox takes up. Since 1 cm³ = 1 ml, this lunchbox could hold 1,000 ml or 1 litre of liquid if it were a container.
Example 3
A jug holds 2 litres of water. If you pour 750 ml of water from the jug, how much water is left in millilitres?
Answer
1,250 ml
Always make sure all measurements are in the same units before you add or subtract them.
Common mistakes
- ✗Confusing volume with capacity, or using the wrong units for each.
- ✗Forgetting to convert units before performing calculations (e.g., adding litres and millilitres directly).
- ✗Incorrectly converting between litres and millilitres (e.g., multiplying by 100 instead of 1,000).
- ✗Forgetting to include the correct units (cm³, ml, or l) in the final answer.
- ✗Using the formula for area (Length × Width) instead of volume (Length × Width × Height) for 3D objects.
Exam tips
- ★Read the question carefully to determine if it's asking for volume or capacity, and what units are required for the answer.
- ★Always write down the units with your numbers throughout your working and in your final answer.
- ★If a problem involves different units (e.g., litres and millilitres), convert them all to the same unit before doing any calculations.
- ★Draw a simple diagram for volume problems to help visualise the cuboid and its dimensions.
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