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The mass of an object tells you how heavy something is. You use grams (g) and kilograms (kg) to measure mass.

• Grams are used when you weigh a lighter item, like an apple or banana.

• Kilograms are used when measuring the mass of a heavier object, like a box of toys or yourself.

1000 g = 1 kg

You can use the greater than (>) , equal to (=) or less than (<) signs to help you compare the mass of two objects.

Don’t forget, the tip of the arrow always points to the smaller number.

Look carefully at the measurements shown on the scales.

The mass of the doughnuts is 500 g, while the fruit weighs 5 kg. But are the doughnuts or pineapples heavier?

Since both foods are being weighed in different units, it would make sense to convert them so it's easier to compare. Let's convert them both to grams.

The doughnuts are already in grams, so you only have to convert the fruit. We know there are 1000g in 1 kg. So:

5 kg = 5000 g

Now you have to compare 5000 g and 500 g - which is the heavier mass?

5000 g > 500 g

5000 g is heavier than 500 g, so the fruit is heavier than the doughnuts.

Look carefully at the measurements shown on the scales.

What do the scales say that the shoes weigh?

The scale with the white shoe points to 1000 g while the black shoe weighs 1 kg.

Just like the last example, it would be easier if you were comparing two measurements with the same units.

Let’s covert 1000 g into kilograms:

1000 g = 1 kg

So the white shoe and the black shoe both weigh 1 kg. Their mass is the same.

Kemi and Mariella both bought a bag of sweets. Kemi’s bag weighed 1300 g and Mariella’s bag had a mass of 1 kg and 500 g. Who had the heavier bag?

Turn the measurements into ones that share the same units.

1300 g = 1 kg and 300 g

It's now easier to see who has the heavier bag of sweets:

• Kemi had 1 kg 300 g
• Mariella had 1 kg 500 g

Mariella bought the heavier bag of sweets.

1300 g < 1 kg 500 g

Find pairs of objects around you to compare and work out which is the lighter of the two and which is the heavier. Be sure to ask an adult for help.

Make a list of the objects from heaviest to lightest.

Can you find two objects that are equal to each other in weight?

Remember

Two things can be the same mass. Smaller things can sometimes be heavier than larger things.