Witches' Brew

This activity explores a simple chemical reaction that creates a huge reaction!

Learning Objectives/Opportunities

  • Build basic knowledge about chemical reactions

  • Science process skills: safe lab practices, measuring, observation

  • Executive Function skills: gross and fine motor skills, self-regulation and control

cauldron.jpeg

Materials:

  • Dry yeast

  • Warm water

  • Liquid dish soap

  • 3% hydrogen peroxide

  • Green Food Coloring

  • Plastic cauldron

Gentle Disclaimer: This experiment involves a fast, messy chemical reaction. We advise this activity be demonstrated outdoors, and upon addition of the yeast, all individuals observing this activity move away from the cauldron until the reaction stops.

Recommended Materials:

  • Safety goggles

Activity Instructions

  1. Measure 1/2 cup of hydrogen peroxide and pour into the cauldron

  2. Squirt in liquid dish soap

  3. Swirl cauldron

  4. Add several drops of green food coloring and swirl until fully colored

  5. In a small bowl, mix together 1 tbsp of yeast and 3tbsp of warm water

  6. Add the yeast mixture to the cauldron and step back!

Examining the Experiment:

This activity occurs because of a chemical reaction between the hydrogen peroxide and the yeast. When these two materials combine, the yeast caused the hydrogen peroxide to break down emitting lots of oxygen gas. The liquid soap acts as an elastic barrier, preventing the gas from escaping resulting in the foamy explosion.

Science Extension: Material Exploration

Liquid soap is an important ingredient because it traps the gas bubbles making the foamy explosion. Attempt to replicate this chemistry activity without the liquid soap. What do you observe? How is this reaction different from or the same as the original witches’ brew? What happens if you add a different barrier, such as corn syrup or glycerin? Do these have different or similar reactions?

Resources

Monster MayhemNatasha ChlebuchChemistry, Chemical Reactions