Practical biology at home - osmosis

Hints and Tips - 7 minute read

Sylvia Grice, OCR Science Subject Advisor

From cell membranes in Entry Level Science to turgidity in A Level Biology, using potato and salt solution is a tried and tested investigation amongst biology teachers and students.

Your students are unlikely to have access to test tubes, cork borers or measuring cylinders at home, but with some creativity this investigation can be adapted for remote learning.

Fundamentally, all that is required is access to some plant tissue (carrot, courgette and beetroot all work well) and a solution. There are so many possible variables within this practical that it lends itself brilliantly to students designing their own investigation. They could consider:

• Plant tissue used:
  • Different vegetables or fruits – such as apple vs beetroot.
  • Shape and volume of cut piece – say a 1cm³ piece vs 3cm³ piece.
  • Surface area of cut piece – a long thin cuboid vs shorter cube.
• Solution:
  • Solute – for example salt vs sugar; blackcurrant squash vs orange juice.
  • Temperature – a hot water bath vs an ice water bath.
  • Concentration – 2 teaspoons of solute vs 4 teaspoons.
  • Volume – 100cm³ vs 200cm^3.

Applying understanding

Having access to only limited equipment encourages students to think outside of the box and apply their understanding in unfamiliar contexts, such as:

• Does their practical method need to be different because they are using pieces of cucumber at home and not potato in a school laboratory?
• Can they use kitchen measuring spoons instead of measuring cylinders?
• Do their bathroom scales have the resolution necessary to measure a change in mass of a piece of carrot or are kitchen scales a better choice?
• Could they use a ruler to measure change in length of apple if they don’t have any scales at all?

Personalisation

This investigation can be linked to a wide range of scientific skills including:

1. Method writing – it is often harder to follow a method written by a peer when they are not working on the table next to you and you can’t just ask them!
2. Performing serial dilutions
3. Making predictions
4. Completing risk assessments
5. Designing results tables
6. Calculations – percentage change, rate of water uptake, identifying the concentration of dissolved substances in the plant tissue
7. Graph drawing – either using printed graph paper or Excel
8. Making conclusions
9. Evaluation – how are conclusions different between students who measured the mass of their beetroot compared to students that measured length?

If using vegetables does not appeal to your students, perhaps a gummy bear alternative may spark their imagination.

Other practicals

For other ideas on adapting practicals for remote learning, check out this blog on investigating waves in physics and keep an eye out for a blog on chemistry practicals coming soon.

Stay connected

If you have any queries or questions, you can email us at science@ocr.org.uk, call us on 01223 553998 or Tweet us @OCR_Science. You can also sign up to subject updates and receive information about resources and support.

About the author

Sylvia Grice – Subject Advisor, Science

Sylvia joined OCR in April 2020 with specific responsibility for A Level Biology. She has come straight from the classroom after 8 years teaching GCSE Science and A Level Biology in Wiltshire and Norfolk with a brief period teaching in America. She is passionate about providing the support needed for excellent teaching and learning. Sylvia holds a degree in Natural Sciences and a PGCE in Secondary Science from the University of Bath. In her spare time Sylvia enjoys travelling around the UK in her campervan with her family.