Chapter Overview


Mass: Comparing, adding and subtracting

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Mass: Comparing, adding and subtracting

​​In a nutshell

Mass is how you describe how heavy an object is. You can compare the weights of objects using mass and you can use a weighing scale or balance to find and compare masses of objects.

Comparing mass

Heavier objects have greater mass, so a 500g500g​ pot is heavier than a 100g100g​ fork. Remember that you can only compare masses if they have the same unit; a 150g150g​book is not heavier than a 5kg5kg​ chair! Use this equation to convert between units:

1000g=1kg1000g = 1kg

Adding and subtracting mass


Make sure the units are the same.
Identify what the question is asking you:
  • "Find the combined mass of ..." means summing the masses.
  • "How much heavier is ..." means subtracting one mass from the other.
Convert the answer back into appropriate units (if required).


How much heavier is a 2.3kg2.3kg​ paperweight compared to a 750g750g​ bottle of water?

2.3kg=2300g2.3kg = 2300g​​

2300750=1550g2300 - 750 =\underline{1550g}

What is the combined weight of the paperweight and the bottle of water?

2.3kg=2300g2.3kg = 2300g

2300+750=3050g2300 + 750 = \underline{3050g}

Frequently Asked Questions (FAQ)


  • Question: What is the biggest unit of mass?

    Answer: The largest unit of mass is the kilogram (kg).

  • Question: Is mass the same as weight?

    Answer: The two terms can be used interchangeably, however mass is not the same as weight.

  • Question: What units are used to measure mass?

    Answer: The units gram (g) and kilogram (kg) are used to measure mass.



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