A-level set practicals – using a potometer


‘Using a potometer’ resource supports the use of practicals across various new 2015 A-level biology specifications (OCR, AQA, Edexcel and Eduqas).

This simple potometer allows students to work individually or in pairs to measure the rate of transpiration of a plant specimen within a one hour lesson. Assembled using low cost parts the apparatus offers an affordable potometer for all your students, giving them a chance to record water loss at regular intervals and an opportunity to investigate the effect of different abiotic factors on the rate of transpiration.

The ‘Making and using a straw potometer‘ offers a quick alternative to demonstrate how to use a potometer to measure the rate of transpiration in a plant. This setup allows students to revise what a potometer does and gives an opportunity for them to investigate further if they want to.

This video demonstrates the method on how to measure transpiration with a potometer.

These resources and this practical allow students to develop their understanding of water transport through plants and factors that affect the rate of diffusion. There is also the opportunity to develop graph drawing skills as well as the ability to calculate rates of change. It provides students with the opportunity to develop (and demonstrate) their skills of taking quantitative measurements as well as their ability to consider variables that need to be controlled.

Through the suggested questioning in the teacher support materials or the student worksheet students can be encouraged to explore the implications of their findings to real life situations.

Materials include:

  • Tested materials to support the A-level practical endorsement (CPAC)
  • Support materials for teachers and technicians
  • Student worksheet to help provide evidence for meeting the practical skills requirements
  • Student revision materials to help prepare for exams

Support materials for other key practicals in A-level specifications can be found on the A-level set practicals main page.

Your FAQs Answered

Q: What plant is best to use?

A: You need a stem that is strong enough to push through the rubber bung and about 4mm in diameter. Often you can find perfect examples in your local area. Laurel being one of them.

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