# A student dissolves 4.0 g of sodium hydroxide (NaOH) in water to make 500 cm³ of solution. Describe how the concentration of this solution would change if the student had instead dissolved the same 4.0 g of sodium hydroxide in only 250 cm³ of water. Explain why this change occurs.

> AQA GCSE Chemistry (8462) — 4.3.4 Using concentrations of solutions in mol/dm³ (Chem only) · Explain · 4 marks

> Concentration is defined as the amount of substance in a certain volume of solution. The relative formula mass of NaOH is 40.

## Mark scheme (4 marks)

1. The concentration would increase / be greater / be higher
2. The concentration would double / be twice as great
3. The same amount (mass/moles) of solute is dissolved in a smaller volume of solvent/solution
4. There are more particles/moles of solute per dm³ (unit volume)

## Key terms

- [concentration](https://www.gradenine.co.uk/glossary/concentration)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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