Grade 6 Mathematics Measurements – Mass Notes
Measurements — Subtopic: Mass
Subject: Mathematics — Level: about 11 years (Kenyan primary school)
What is mass?
Mass tells us how much matter is in an object. We measure mass to know how heavy something is in everyday life. In school and in Kenya we usually use the metric units: kilograms (kg) and grams (g).
Common units of mass
- Kilogram (kg) — used for heavier items (baskets of maize, sacks, people).
- Gram (g) — used for lighter items (sugar packets, fruits).
- Milligram (mg) — very small masses (medicine doses).
- Tonne (t) — very large mass (trucks of grain). 1 tonne = 1000 kg.
- 1 kg = 1000 g
- 1 g = 1000 mg
- 1 tonne = 1000 kg
Measuring mass — tools
You can measure mass using:
- Kitchen balance or two-pan balance (shows which side is heavier).
- Electronic/ bathroom scale (gives direct numbers in kg and g).
- Spring scale (less common at school).
Examples from everyday life (Kenyan contexts)
- A small sugar packet might be 250 g.
- A litre of water has mass about 1 kg — so a 20 L jerrican of water ≈ 20 kg.
- A big maize bag used in markets might be about 90 kg (varies).
Worked examples
Convert 2.5 kg to grams.
1 kg = 1000 g → 2.5 kg = 2.5 × 1000 g = 2500 g.
Add 1.25 kg and 750 g.
- Change 1.25 kg to grams: 1.25 × 1000 = 1250 g.
- 1250 g + 750 g = 2000 g.
- 2000 g = 2 kg.
Answer: 2 kg.
Which is heavier: 500 g or 0.6 kg?
0.6 kg = 0.6 × 1000 = 600 g. So 600 g > 500 g. Therefore 0.6 kg is heavier.
Short activities (do these in class or at home)
- Use a kitchen scale: weigh a mango, a cup of flour and a small tomato. Record the mass in g or kg.
- Find two classroom objects and say which has greater mass. Explain why.
- Convert these: (a) 4500 g to kg, (b) 3.75 kg to g, (c) 2500 g to kg.
Quick practice quiz
- Convert 5.2 kg to grams.
- Add: 2 kg + 350 g + 450 g.
- Which is lighter: 1500 g or 1.6 kg?
- If 1 litre of milk ≈ 1 kg, what is the mass of 5 litres?
Answers (click to show)
- 5.2 kg = 5200 g.
- 2 kg = 2000 g; 2000 + 350 + 450 = 2800 g = 2.8 kg.
- 1.6 kg = 1600 g, so 1500 g is lighter.
- 5 litres ≈ 5 kg.
Important note — mass vs weight
Mass is the amount of matter and is measured in kg, g. Weight is the force of gravity on that mass and is measured in newtons (N). In primary school you will usually work with mass in kg and g — when people say "how heavy?" they mean mass.