Elephant Toothpaste – The Chemistry

Two weeks ago, I wrote about the Elephant Toothpaste experiment I did with my students. A few readers who read that post were curious about how to conduct the experiment and what happens in it. Hence, this follow-up post on the Chemistry behind the experiment. Incidentally, my lesson plan for the next Chemistry class followed the same thought process.

Chemical reaction

The chemical reaction that produces the Elephant Toothpaste‘ effect is – decomposition of Hydrogen Peroxide. Hydrogen Peroxide, in the presence of a catalyst, decomposes rapidly into Water and Oxygen. The chemical equation is as shown in the figure below.

Chemical Equation of Hydrogen Peroxide Decomposition

The catalyst we used in our experimental setup was Potassium Permanganate (KMnO4). Other suitable catalysts are Yeast and Potassium Iodide (KI) among many others.

We used Hydrogen Peroxide (6% v/v solution in water) and crystalline Potassium Permanganate; both are available in Medical stores.

The hydrogen Peroxide solution is generally unstable and undergoes slow decomposition in the presence of sunlight. That is why concentrated solutions are stored in dark coloured containers. In the presence of a catalyst, however, the decomposition reaction speeds up. This acceleration is responsible for the ‘Elephant Toothpaste’ effect.

Safety precaution: Hydrogen Peroxide in its pure form is highly unstable and should be handled only by experienced professionals in a laboratory setting.

Chemistry to show-biz

On its own, the chemical decomposition of aqueous Hydrogen Peroxide is quite unspectacular. It happens gradually and because the products are Water and Oxygen, there is no noticeable change either.

To convert this into a visual treat, additional materials are used. In this experiment, the catalyst, food colouring, liquid soap, and the shape of the reaction container play different roles in creating the visual effects.

The visual effects can be varied depending on the choice of catalyst and concentration of Hydrogen Peroxide solution. Watch these videos below to observe different forms of this effect.

Do It Yourself

Here is a simple step by step guide to conduct this experiment at home.

Ingredients

  • Hydrogen Peroxide (6% v/v solution)
  • Potassium Permanganate crystals
  • Food colouring
  • Liquid soap (dish-washing liquid is best)
  • Empty container (a ½ litre transparent plastic bottle or a tall transparent glass of ½ litre capacity)

Safety precautions

  • Conduct it with adult supervision only
  • Avoid direct contact of Hydrogen Peroxide and Potassium Permanganate with skin
  • Have children observe from a safe distance (preferably 3 feet)

Procedure

  1. Place the container on a flat surface (table, ground, or a flat tray) – Outdoor location works best; if indoors, choose a well-ventilated area
  2. Add ¼ teaspoon of food colouring (10-12 drops if in liquid form) into the container
  3. Add 1 teaspoon of liquid soap
  4. Pour ~150 ml of Hydrogen Peroxide solution
  5. Shake well to mix the colour
  6. Add ½ teaspoon of Potassium Permanganate
  7. Shake the container gently
  8. Step away and observe

Note: Because Potassium Permanganate has a vivid purple colour, it generally masks the colour of food colouring. You could try the same experiment with 2 teaspoons of yeast to remove this colour masking effect.

Clean Up

  1. After the reaction is complete, clean up the container with water and soap
  2. Clean up the reaction area with water and soap as well (table, tray, floor etc.)
  3. Do not use the container again for any food or drink

We hope you enjoyed learning the Chemistry behind the experiment. We would love to hear about your experience conducting this at home with your kids. Do share your feedback, photos, and videos with us.

Until next time, continue to stay curious!

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Featured Image credits: deepakrit from Pixabay

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Dr. Soumya Sreehari

Dr. Soumya Sreehari

Co-Founder and Specialist at NumberNagar®
Dr. Soumya is an Educator and Researcher with a passion for reading, writing and teaching. She holds a PhD in Chemistry (Michigan Technological University, Houghton, USA). Her experience as a student and a teacher in two countries led her to pursue a career in Education. Her core work at NumberNagar® involves quality delivery of product and services at every stage of the customer life cycle. She leads the team that makes this happen. Previously she has taught Chemistry to first year undergraduate students at Michigan Technological University. She is a voracious reader and challenges herself to read 50 books every year.

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