Grade 9 Liquid Measurements: Short Notes

9 ශ්‍රේණිය · 9 පරිච්ඡේදය · ද්‍රව මිනුම්

83%

of Grade 9 term tests include it (33 of 40)

226

marks in past papers (46 questions)

9 min

full lesson with quick checks

🎯 What you'll learn

Use 1 ml = 1 cm³ and 1 l = 1000 cm³
Use 1 m³ = 1000 l
Convert between ml, l, cm³ and m³
Find the capacity of a cuboid tank in litres
Solve filling and flow-rate problems

The black tank on your roof

Many Sri Lankan houses have a 1000-litre water tank on the roof. A box-shaped tank of that size measures about 1 m × 1 m × 1 m. That's no accident: one cubic metre holds exactly 1000 litres. Today we connect litres and millilitres with cm³ and m³.

Volume and capacity

Volume is the space something takes up: measured in cm³ or m³.Capacity is how much liquid a container can hold: measured in ml or l.The capacity of a container is the volume of liquid that fills it, so the two kinds of units must be linked.Remember: 1 l = 1000 ml.

The key link: 1 ml = 1 cm³

A tiny box 1 cm × 1 cm × 1 cm, about the size of a sugar cube, holds exactly 1 ml of water.So 1 cm³ = 1 ml.A 5 ml medicine spoon holds 5 cm³; a 250 ml glass holds 250 cm³.

One litre is a 10 cm cube

A cube with 10 cm edges has volume 10 × 10 × 10 = 1000 cm³. That is 1000 ml, which is 1 litre. So 1 l = 1000 cm³.

🧮 All the links

A 1 m cube is 100 cm on each side: 100 × 100 × 100 = 1 000 000 cm³, which is 1000 litres. Going to a smaller unit, multiply; going to a bigger unit, divide.

1 ml = 1 cm³ 1 l = 1000 cm³ 1 m³ = 1 000 000 cm³ = 1000 l

✏️ Quick conversions

Convert (i) 2.5 l to ml (ii) 750 cm³ to litres (iii) 3.2 m³ to litres (iv) 4500 l to m³.

1(i) 2.5 × 1000 = 2500 ml.
2(ii) 750 cm³ = 750 ml = 750 ÷ 1000 = 0.75 l.
3(iii) 3.2 × 1000 = 3200 l.
4(iv) 4500 ÷ 1000 = 4.5 m³.

✅ (i) 2500 ml (ii) 0.75 l (iii) 3200 l (iv) 4.5 m³

⚠️ Moving the point the wrong amount

O/L examiners found many candidates shifting the decimal point wrongly when multiplying by 1000. 0.035 l is 35 ml, not 350 ml. Fill the gaps with zeros: 0.035 → 0035. → 35.Check the size: a litre is 1000 ml, so 0.035 l must be a small amount, well under 100 ml.

✏️ Capacity of a tank

A cuboid-shaped water tank at a Hambantota school is 2 m long, 1.5 m wide and 1 m high. Find its capacity in litres.

1Volume = length × width × height = 2 × 1.5 × 1 = 3 m³.
21 m³ = 1000 l, so capacity = 3 × 1000 = 3000 l.

✅ 3000 l

⚠️ Same units before dividing

How many 250 ml glasses can be filled from 4.5 l? Dividing 4.5 by 250 gives nonsense. In an O/L paper many candidates did not convert first. Change to the same unit: 4.5 l = 4500 ml, and 4500 ÷ 250 = 18 glasses.

📌 Remember

• 1 ml = 1 cm³ and 1 l = 1000 ml = 1000 cm³.• 1 m³ = 1000 l.• To a smaller unit multiply by 1000; to a bigger unit divide by 1000.• Capacity of a cuboid tank: length × width × height, then convert.• Put quantities in the same unit before dividing; time = amount ÷ rate.

🧾 Quick revision sheet

1 cm³ = ? ml	1 ml
1 l = ? cm³	1000 cm³
1 m³ = ? litres	1000 l
Litres to millilitres	Multiply by 1000.
cm³ to litres	Divide by 1000.
Volume and capacity: what's the difference?	Volume is space taken up (cm³, m³); capacity is liquid a container holds (ml, l).
Time to fill a tank	Time = amount ÷ rate (same units).