Mathematics — Measurements

Subtopic: Mass

Target age: 8 (Kenya)

• Know what mass means.
• Use grams (g) and kilograms (kg).
• Compare objects: heavy or light?
• Do simple additions and conversions between g and kg.

What is mass?

Mass tells us how much matter is in an object — how heavy something is. We measure mass using a scale or balance.

Units we use

In Kenya we use the metric system:

• Gram (g) — small things (e.g., a banana about 120 g)
• Kilogram (kg) — 1 kg = 1000 g (used for heavy things, e.g., a 1 kg bag of sugar)

Examples (easy)

Compare: heavy or light?

Look at two objects and ask: Which is heavier? Which is lighter?

Answer: Mango (300 g) is heavier than banana (120 g).

Simple adding and converting

Add grams, then convert to kilograms if 1000 g or more.

Try these (do them yourself)

1. A mango = 250 g and a banana = 120 g. What is their total mass?
2. Which is heavier: a 1 kg packet of maize flour or two stones of 600 g each?
3. Convert 1500 g into kg and g.
4. If a small fish is 400 g and a bigger fish is 900 g, how much do they weigh together? Write in kg and g.
5. A kilogram of rice costs money in a shop. If you buy 2 kg, how many grams is that?

Answers

1. 250 g + 120 g = 370 g.
2. Two stones of 600 g each = 1200 g = 1 kg 200 g → stones are heavier than 1 kg packet.
3. 1500 g = 1 kg 500 g.
4. 400 g + 900 g = 1300 g = 1 kg 300 g.
5. 2 kg = 2000 g.

Home activity

With an adult, use a kitchen scale. Weigh 5 things in your kitchen and write their masses. Put them in order from lightest to heaviest.