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Turmeric pH Indicator Experiment for Acids & Bases

Turmeric pH Indicator Experiment for Acids & Bases

This turmeric pH indicator experiment for acids and bases is a fun, easy way to learn about acids and bases. If done with gentle household items like vinegar, lemon juice, baking soda, etc. it is safe even for young children.  

Turmeric is a natural pH indicator. It changes colour in the presence of acids and bases. In the presence of acids, turmeric remains yellow, but in the presence of alkaline substances (bases), it turns red. It is ideal to use it for doing experiments with vinegar or citric acid and baking soda.

pH and chemical reaction – A simple summary

The pH is the measure of how acidic or basic (alkaline) a substance is. It is represented in a numerical range from 0 to 14, with seven being neutral. The more acidic the material, the closer it is to 0, the more basic, the closer it is to 14.  The pH number indicates the presence or absence of hydrogen ions. Acids have hydrogen ions (H+), and bases have hydroxide ions (OH-). The higher the concentration of these ions, the more acidic or basic the substance. 

When an acid and base come in contact with one another, a chemical reaction occurs. Acids and bases neutralize one another by breaking apart and forming into new substances. The reaction always results in the creation of water (H2O) and a salt. 

Turmeric pH Indicator Experiment for Acids & Bases

If you want some more information about pH and colour changing experiments, you may want to see my Color pH Baking Soda and Vinegar Science Experiment.

What you need for a turmeric pH indicator experiment for acids and bases

  • Turmeric
  • Baking soda/bicarbonate of soda
  • Vinegar, lemon juice or citric acid
  • Water
  • Bowl
  • Spoon
  • Ice cube tray (optional)
  • Tray
  • Pipettes

There are different ways to do this experiment to make it exciting and fun for children. 

The simplest way is for children to add different substances to some turmeric to see what happens. They could test substances such as lemon juice, soda, baking soda, water, etc. to see which one cause turmeric to change colour.

Once they have explored using turmeric as an indicator, they can have some fun with it. One option is to take some baking soda and mix in some turmeric. I usually use 2-3 teaspoons of turmeric for every ½ cup of baking soda. You will also need to add in a few teaspoons of water to help mix it all together. Once it is well combined, spread it out on a tray. Children can then squirt lemon juice or vinegar onto it using a pipette to see what happens.

Alternatively, you can also try freezing the baking soda. 

To do this, prepare the turmeric, baking soda and water mixture as above. However, you may need to add a little more water to this mixture so that it will stick together. Scoop it into ice cube trays or moulds and place it in the freezer for several hours. 

Once it is frozen, children can place the frozen cubes in a plate or bowl full of vinegar or citric acid. Alternatively, they can squirt the cubes with vinegar to create a reaction.

Questions to ask

  • What do you notice about the reaction?
  • What happens to the turmeric when it comes into contact with different substances?
  • Is there a difference when you freeze the bicarbonate of soda rather than leave it room temperature?
  • What do you notice when you combine the baking soda and vinegar when the turmeric is present?
  • Could you think of a way to prove that a new substance is created after the reaction? What could you do?
  • What happened? Why do you think it happened? What did you learn?
  • Is there anything more you would like to try out or test?

What they get from it

This experiment will help children to explore the changes in pH that occur as part of a chemical reaction. They may also begin to think about whether there might be other ways to demonstrate that new and different substances form as part of a chemical reaction. This hands-on activity will teach them to predict, observe, record and discuss, or present their findings. Doing experiments will provide children with an opportunity to write by recording their observations with notes or drawings. Children enjoy doing experiments, and it can be highly motivational to write, even for more reluctant writers.

Research shows that people learn best (for long-term memory at least) when they learn through hands-on, practical experiences. (Hearns, Miller & Nelson, 2009; Hillman, 2011; Ferri, B.H., Ferri, A.A., Majerich, D.M., Madden, A.G., 2016). It’s also an opportunity for children to begin to develop scientific thinking. Furthermore, inquiry-based learning will encourage children’s curiosity and love of learning. (Ambrose et al. 2010; Froyd 2008; Prince & Felder, 2007; Springer, Stanne & Donovan, 1999). 

Take it further

See my other vinegar and baking soda experiments so that children can explore chemical reactions: 

It can be great for children to create their own experiments based on what they want to find out. Allow them to ask questions to extend their learning. Ask them: What questions do you have about these reactions? Can you design an experiment to answer one of the questions?

They may want to see if they can find the exact amount of vinegar to make the baking soda react. They might want to see if a frozen baking soda ball reacts faster with vinegar than a dried baking soda ball. Alternatively, they may want to see if there is a difference in the reaction between vinegar and citric acid. 

I hope that you enjoy trying out using turmeric as a pH Indicator in an experiment with acids & bases.

References

Ambrose, S. A., Bridges, M. W., DiPietro, M., Lovett, M. C., & Norman, M. K. (2010). How learning works: Seven research-based principles for smart teaching. San Francisco, CA: Jossey-Bass. https://books.google.com/books

Ferri, B.H., Ferri, A.A., Majerich, D.M., Madden, A.G. (2016). Effects of In-Class Hands-On Laboratories in a Large Enrollment, Multiple Section Blended Linear Circuits Course. Advances in Engineering Education, 5 (3). https://files.eric.ed.gov/fulltext/EJ1121997.pdf

Froyd, J. E. (2008). White paper on promising practices in undergraduate STEM education. Commissioned paper, Board on Science Education, National Academies. Retrieved from https://sites.nationalacademies.org/DBASSE/BOSE/DBASSE_080106#.UUoV5hngJ8g

Hearns, M.K., Miller, B.K. and Nelson, D.L. (2009). Hands-On Learning versus Learning by Demonstration at Three Recall Points in University Students. OTJR: Occupation, Participation and Health, 30 (4), 169-171. https://journals.sagepub.com/doi/10.3928/15394492-20090825-01

Hillman, C.N. (2011). The effects of hands-on learning versus learning by demonstration on memory in community-dwelling older adults (Doctoral dissertation, The University of Toledo). Retrieved from https://pdfs.semanticscholar.org/6231/d55fc1c730ec086f012677c54141f466e18e.pdf

Prince, M., & Felder, R. (2007). The many facets of inductive teaching and learning. Journal of College Science Teaching, 36(5), 14–20. https://s3.amazonaws.com/academia.edu.documents

Springer, L., Stanne, M. E., & Donovan, S. (1999). Measuring the success of small-group learning in college-level SMET teaching: A meta-analysis. Review of Educational Research, 69, 21–51. http://archive.wceruw.org/cl1/CL/resource/scismet.pdf

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