Weird science with a PC professor

You don’t have to be a mad scientist to have fun on Halloween. Dr. Seann P. Mulcahy of the Providence College Department of Chemistry and Biochemistry demonstrates an experiment you can try at home.


In a cup, mix

  • 2 tbsp of hydrogen peroxide
  • Food coloring
  • Dish soap

In a second cup, mix:

  • 4 tbsp of warm water
  • 1 package of dry yeast

Put the cup with the peroxide solution in the pumpkin. Then pour the contents of the yeast solution into the peroxide solution.


The yeast serves as the catalyst in this reaction, speeding up decomposition of hydrogen peroxide into water and oxygen gas. The gas is captured in the bubbles that are generated because of the soap solution.

You will also notice steam, or water vapor, rising up from the pumpkin. This happens because breaking down hydrogen peroxide releases heat.

Music: Spooky Ride by Twin Musicom is licensed under a Creative Commons Attribution license (



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