Solve the mystery of solvents
Revise the terms solvent, solute and solution, and help learners to appreciate that not everything will dissolve in water.
For the more able:
To introduce the idea that water dissolves things which have a charge or are polar but not things which are uncharged or non-polar.
To provide an opportunity to discuss the concepts of the reliability and limits of evidence.
Notes on the activity
- This activity is straightforward. It will take no more than 15 minutes (including time for students to fill in the table) once the nail varnish is dry.
- The nail varnish will take a while to dry so ask students to paint it on a white tile early on in the lesson. If behaviour is a problem, you might wish to consider using a fast drying nail varnish. Students can copy the table ready for completion and answer the introductory questions while the nail varnish dries.
- Hydrochloric acid is included in the table because students often think acids will dissolve anything.
- The practical activity itself does not take very long – its purpose is to provide an opportunity for discussing why things dissolve and the limits of the evidence available.
- The extension sheet entitled Dissolving asks students to explain why some substances dissolve and others do not. This exercise is aimed at more able students.
- Nail varnish – a dark colour will work best (try not to use old, dried up nail varnish and have several bottles available to reduce waiting times)
- White tile – if these are in short supply, glass beakers also work well but do not use anything made of plastic
- Ethanol (Highly flammable) – ensure all solvent bottles have the correct hazard labels on them. See CLEAPSS Hazcard HC040a
- Propanone (acetone) (Highly flammable and irritant). See CLEAPSS Hazcard HC085a
- Ethyl ethanoate (Highly flammable and irritant). See CLEAPSS Hazcard HC043a
- Hydrochloric acid 1 mol dm–3 (or less concentrated) (Irritant). See CLEAPSS Hazcard HC047a
- Cotton wool pads – you can cut them into quarters to make them last
- Access to water
- Eye protection.
You may like to provide students with bottles of commercial nail varnish remover for comparison, especially if you can find one with the solvents it contains listed on the packaging.
What to do
- Paint five nail-sized areas of the white tile with a thin layer of nail varnish.
- Keep them about 3 cm away from each other.
- While the nail varnish dries, copy the chart below and fill in the prediction column.
|Will it remove the nail varnish?
|Does it remove the varnish in one go?
|Does it remove the varnish eventually?
|Put the substances you have tested in order from 1 (best) to 5 (worst).
|What problems might there be with this remover? (Hint: check the hazards)
|Ethanol – Highly flammable
|Propanone – highly flammable and irritant
|Ethyl ethanoate (Highly flammable and irritant)
|Hydrochloric acid (Irritant)
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Nail varnish removal