Year 2: Kilograms and grams
Part of the Year 2 length, mass, capacity and temperature chapter. Chapter overview · whole chapter on one page
Kilograms and grams
Mass tells us how heavy something is.
A gram is a small unit. We write it as g. Use g for an apple.
A kilogram is a bigger unit. We write it as kg. Use kg for a bag of rice.
There are 1000 g in 1 kg.
Key ideas
- A gram (g) is a small unit. Use it for light things.
- A kilogram (kg) is a bigger unit. Use it for heavy things.
- 1 kg = 1000 g.
- A balance shows when two things weigh the same.
Method. Think about the size of the thing before you choose the unit.
- Think about how big it is. A bag of rice is heavy. Use the bigger unit.a bag of rice
- Choose the unit that fits. kg is the right size for a bag of rice.kg
- Write the answer. kg
Check. Would another unit feel right? No. ✓
Watch out. Small things use small units. Big things use big units.
Method. The object weighs the same as the weights. Add the weights together.
- Look at the weights on the right. The weights balance the object on the left.500 g + 200 g + 100 g
- Change any kilograms to grams. 1 kg = 1000 g.500 + 200 + 100 = 800
- Write the answer. The object weighs the same as the weights.800
Check. Add the weights again in a different order: 100 + 200 + 500 = 800. ✓
Watch out. Change kilograms to grams before you add. 1 kg = 1000 g.
Method. Change to the same unit, then pick the biggest amount.
- Look at A. A is 1 kg.A: 1000 g
- Look at B. B is 900 g.B: 900 g
- Pick the one with the biggest amount. Once the units match, the numbers can be compared.A wins
- Write the answer. A
Check. Compare the other amounts too. ✓
Watch out. Read the units first. 2 m is longer than 150 cm, because 2 m = 200 cm.
Watch out
Watch out: a kilogram is heavier than a gram.
Change to the same unit before you compare.
Exam tip
Grown-up tip. Use a kitchen scale and a bag of flour. Ask: “Is this a gram or a kilogram?”
Exercise 5C Kilograms and grams
Non-calculatorMethod. Think about the size of the thing before you choose the unit.
- Think about how big it is. An apple is light. Use the smaller unit.an apple
- Choose the unit that fits. g is the right size for an apple.g
- Write the answer. g
Check. Would another unit feel right? No. ✓
Watch out. Small things use small units. Big things use big units.
Method. Think about the size of the thing before you choose the unit.
- Think about how big it is. A bag of rice is heavy.a bag of rice
- Choose the unit that fits. kg is the right size for a bag of rice.kg
- Write the answer. kg
Check. Would another unit feel right? No. ✓
Watch out. Small things use small units. Big things use big units.
Method. Each kg is 1000 g. Multiply.
- Know the rule. 1 kg is the same as 1000 g.1 kg = 1000 g
- Multiply. Multiply the number of kg by 1000.2 × 1000 = 2000
- Write the answer. 2000
Check. Share it back: 2000 g is 2 lots of 1000 g. ✓
Watch out. Multiply when you change to a smaller unit. There are 1000 g in 1 kg.
Method. The object weighs the same as the weights. Add the weights together.
- Look at the weights on the right. The weights balance the object on the left.500 g + 300 g
- Change any kilograms to grams. 1 kg = 1000 g.500 + 300 = 800
- Write the answer. The object weighs the same as the weights.800
Check. Add the weights again in a different order: 300 + 500 = 800. ✓
Watch out. Change kilograms to grams before you add. 1 kg = 1000 g.
Method. Look where the needle points, then read the number on the dial.
- Find where the needle points. The needle points to a number on the dial.needle at 3
- Read the number. The numbers on this dial are kilograms.3 kg
- Write the answer. 3
Check. The scale reads 3 kg. ✓
Watch out. The numbers on this dial go up by one kilogram each time.
Method. Look where the needle points, then read the number on the dial.
- Find where the needle points. The needle points to a number on the dial.needle at 4
- Read the number. The numbers on this dial are kilograms.4 kg
- Write the answer. 4
Check. The scale reads 4 kg. ✓
Watch out. The numbers on this dial go up by one kilogram each time.
Method. Change to the same unit, then pick the biggest amount.
- Look at A. A is 2 kg.A: 2000 g
- Look at B. B is 1500 g.B: 1500 g
- Pick the one with the biggest amount. Once the units match, the numbers can be compared.A wins
- Write the answer. A
Check. Compare the other amounts too. ✓
Watch out. Read the units first. 2 m is longer than 150 cm, because 2 m = 200 cm.
Method. Change to one unit, then put the smallest amount first.
- Look at B. B is 500 g.B: 500 g
- Look at C. C is 1 kg.C: 1000 g
- Look at A. A is 2 kg.A: 2000 g
- Put the amounts in order. Smallest firstB, C, A
- Write the letters. B, C, A
Check. Check each pair: the first is never bigger than the next. ✓
Watch out. Compare the numbers after you change to the same unit.
Method. Find the difference by taking the smaller amount away from the bigger one.
- Find the bigger amount. The bigger bag is 1000 g.1000 g
- Find the smaller amount. The smaller bag is 300 g.300 g
- Take the smaller amount away. Subtract to find the difference.1000 − 300 = 700
- Write the answer. 700
Check. Add the difference back: 300 + 700 = 1000. ✓
Watch out. Start with the bigger number, then take the smaller one away.
Method. Change the kilogram to grams, then compare.
- Look at 1 kg. One kilogram is 1000 grams.1 kg = 1000 g
- Compare with 1000 g. The two amounts are the same.1000 g = 1000 g
- Decide. Tom is not right. 1 kg is not lighter than 1000 g.No
Check. They are the same, so neither is lighter. ✓
Watch out. 1 kg and 1000 g are the same mass.
Method. Add all the mass together.
- Find each part. We add the mass together.2000 g + 500 g
- Add them together. Add one part at a time.2000 + 500 = 2500
- Write the answer. 2500
Check. Add in a different order to check: 500 + 2000 = 2500. ✓
Watch out. Use the same unit for every part. The answer is in g.