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Water Electrolysis with Biobased/Low Hazard Indicators – Red Cabbage Juice or Pea Flower Tea

Water Electrolysis with Biobased/Low Hazard Indicators – Red Cabbage Juice or Pea Flower Tea
Contributors
Dean Campbell
Professor | Bradley University
cmwoodbridge
Professor of Chemistry | Georgia Gwinnett College
Saskia van Bergen
Free Range Chemist | H2L Consulting
Beyond Benign
Beyond Benign, Inc.
Setup for the electrodes and gas collection pipets. Each pipette/pencil assembly was placed in a 50 mL beaker filled about halfway with electrolyte and pea flower tea solution. The other end of each sharpened pencil was connected by clips to a 9 V battery.
Summary
Electrolysis of water is carried out using biobased/low hazard indicators to help illustrate the reaction.

Key Chemistry References for this activity:
1) Skinner, J. F. “Red Cabbage and the Electrolysis of Water.” J Chem. Educ., 1981, 58, 1017. https://pubs.acs.org/doi/pdf/10.1021/ed058p1017.1
2) Hugerat, M.; Abu-Much, R.; Basheer, A.; Basheer, S. “Using Inexpensive to Free Materials to do Electrolysis Experiments with All School Ages.” Chem. Educ. J., 2009, 13. http://www.edu.utsunomiya-u.ac.jp/chem/v13n2/13M_Hugerat/M_Hugerat.html

Additional Credit to Kathy Hall from Hilltop Heritage Middle School (retired) who shared her experience teaching the resource developed by the University of Washington Clean Energy Insitute (https://www.cei.washington.edu/lesson-plans/electrochemical-chameleon/)
Keyword Tags
Electrochemistry
Acid-Base Chemistry
Electron Transfer
File (PDF, PPT, image, etc)
electrochemistry-lab-_0.docx
Learning Goals/Student Objectives
In performing this experiment, a student will
- Construct and identify the components of an electrolysis cell.
- Describe how the energy from a spontaneous battery reaction can drive a nonspontaneous electrolysis process.
- Compare how this electrolysis process resembles commercial electrolysis for hydrogen production.
- Contrast the process of hydrogen production by electrolysis with hydrogen production by the petrochemical industry and consider the “greenness” of hydrogen production by water electrolysis.
- Compare the “greenness” of the pH indicators in this lab experiment with other pH indicator systems.
Object Type
Laboratory experiment
Audience
Introductory Undergraduate
Common pedagogies covered
Hands-on learning
Green Chemistry Principles
Safer Chemistry for Accident Prevention
U.N. Sustainable Development Goals (SDGs)
Sustainable Cities and Communities
Safety Precautions, Hazards, and Risk Assessment
- Red Cabbage or Pea Flower Tea
- magnesium sulfate heptahydrate CAS #10034-99-8 (on the Safer Chemical Ingredient List as a Processing Aid and Additive- https://www.epa.gov/saferchoice/safer-ingredients)
- hydrogen gas CAS #1333-74-0 (Generated in experiment)
- oxygen gas CAS #7782-44-7 (Generated in experiment)

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Submitted by

Saskia van Bergen
Published on
Moderation state
Published
Collection
Greener General Chemistry Labs
Time required (if applicable)
The entire experiment should take less than 2 hours.

Comments

Saskia van Bergen
Fri, 08/15/2025 - 08:40 Permalink

Hi Lauren,

I have not used this activity in a classroom with students as I mostly develop content with educators and develop and lead teacher trainings. I have done the electrolysis portion in a training and it was a fairly easy set up and short experiment (final observation is at 10 minutes). I would expect that this experiment with majority of the questions should take less than 2 hours but, if you assign a pre-lab, you could have some of the questions there.

 

Bob Worley
Tue, 07/22/2025 - 02:08 Permalink

Hello

You might like to look at https://www.youtube.com/watch?v=sogxTMossn8 , in which I use drawing pins/thumbtacks as the electrodes. You could use the red cabbage or butterfly pea tea extracts as well. The surprising aspect is that the base of the plastic gallipot does not leak after inserting the drawing pins. The wires of the battery connecting leads are attached by Sellotape or trapped in the tack as shown. The use of syringes means that gases can be extracted and tested with additional experiments. Sodium sulphate (1M) is the electrolyte, as this does not form precipitates. However, the pins do corrode. They can only be used once. I have now removed the pins and replaced them, again with no leaks

By the way, I cannot access the first resource, as I have to pay lots of money. Are school teachers automatically members of the ACS? The second resource mentions the late Peter Schwarz, who I knew when I joined the international microscale family in 2012. He gave me so much encouragement. Microscale approaches are becoming popular in the UK, and we are holding a celebration at https://sites.google.com/view/13ismc26/home. Please show interest using the form on the first page.

Another tip is to use "unbreakable" 2mm carbon fibre electrodes in place of pencil leads.
the UK

Bob Worley FRCS 

Saskia van Bergen
Fri, 08/15/2025 - 08:21 Permalink

Hi Bob,

Thanks for sharing your video.

The main resource is here- electrochemistry-lab-_0.docx the other two items you mentions are references that were used to create the activity (in addition to https://www.cei.washington.edu/lesson-plans/electrochemical-chameleon/ ) and the first articl you mentioned, does not appear to be open access.

Best,

Saskia

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