Concentration – IGCSE Chemistry Definition
IGCSE Chemistry definition of concentration: the amount of solute dissolved in a given volume of solution, in g/dm3 or mol/dm3. Covers calculations and conversions.
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Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Concentration tells you how much solute is dissolved in a given volume of solution. It is a core concept in the stoichiometry section of the 0620 syllabus and is tested in titration calculations, rate of reaction experiments, and acid-base theory. You must be able to calculate concentration in both g/dm³ and mol/dm³.
The 0620 definition
Concentration is the amount of solute dissolved in a given volume of solution. It is measured in g/dm³ (grams per cubic decimetre) or mol/dm³ (moles per cubic decimetre).
Key formulae
Concentration in g/dm³:
Concentration (g/dm³) = mass of solute (g) / volume of solution (dm³)
Concentration in mol/dm³:
Concentration (mol/dm³) = moles of solute (mol) / volume of solution (dm³)
Converting between the two:
Concentration (g/dm³) = concentration (mol/dm³) x molar mass (g/mol)
Unit conversions
- 1 dm³ = 1000 cm³
- To convert cm³ to dm³: divide by 1000
- Always convert volumes to dm³ before using the formulae
Worked examples
A solution contains 4.0 g of NaOH in 500 cm³. Calculate the concentration in g/dm³.
Volume = 500 / 1000 = 0.5 dm³
Concentration = 4.0 / 0.5 = 8.0 g/dm³
Convert 8.0 g/dm³ NaOH to mol/dm³. (Mr of NaOH = 40)
Concentration = 8.0 / 40 = 0.2 mol/dm³
Worked exam question
25.0 cm³ of hydrochloric acid was used in a titration. The concentration of the acid was 0.10 mol/dm³. (a) Convert 25.0 cm³ to dm³. (1) (b) Calculate the number of moles of HCl used. (1)
Mark scheme
(a) 25.0 / 1000 = 0.025 dm³ [1]
(b) Moles = concentration x volume = 0.10 x 0.025 = 0.0025 mol [1]
Common exam mistakes
- Forgetting to convert cm³ to dm³. The formula uses dm³. If you use cm³ without converting, your answer will be wrong by a factor of 1000.
- Confusing concentration with amount. Concentration is amount per unit volume. You can have a large volume of dilute solution that contains more solute than a small volume of concentrated solution.
- Mixing up concentrated/dilute with strong/weak. Concentrated/dilute refers to how much solute is dissolved. Strong/weak (for acids) refers to how fully the acid ionises.
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