Calculating the volume of a certain number of moles
3 marks · NormalA student wants to find out whether the volume given for a gas in a chemistry problem should be recorded in cm³ or dm³. They know that 1 dm³ is equal to 1000 cm³.
Explain which unit (cm³ or dm³) is more suitable for measuring the volume of a sample of air collected from a 3-litre container, and describe how to convert between these units.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Also accept: States or explains dm³ is preferred for 3 litres; describes the conversion process; gives the correct conversion factor.
Common mistakes: Using litres directly without conversion; confusing multiply/divide factors; not stating which unit is more suitable.
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Marking points
B1 · 1 mark · States that dm³ is the more suitable unit for a 3-litre (large) sample.
M1 · 1 mark · Describes or states the correct conversion factor between cm³ and dm³ (multiply or divide by 1000).
M2 · 1 mark · Correctly explains which direction to multiply or divide for each conversion (e.g., cm³ to dm³: divide by 1000; dm³ to cm³: multiply by 1000).
Worked solution
For a large volume such as 3 litres, it is more suitable to use dm³, because 1 dm³ = 1 litre and this is the standard unit for large gas or liquid volumes in chemistry.
To convert from dm³ to cm³, you multiply the number of dm³ by 1000 (since 1 dm³ = 1000 cm³). To convert from cm³ to dm³, you divide by 1000.
So, for example, 3 dm³ = 3 × 1000 = 3000 cm³. Conversely, 3000 cm³ = 3000 ÷ 1000 = 3 dm³.