Bath Bombs: An Inexpensive and Accessible Kinetics Experiment

In this fun and colorful experiment, students make their own bath bombs and investigate the effect of temperature on reaction rates.

by Meaghan Cabassa and Beth L. Haas*

J. Chem. Educ. 2020, 97, 6, 1629–1632

Abstract: Cosmetic chemistry is a prevalent part of everyday life, but there are very few undergraduate laboratories that explore this topic. Here, we present a laboratory exercise in which students use fizzing bath tablets (better known as “bath bombs”) to learn about introductory kinetics. Students created their own bath bombs by combining citric acid, baking soda, and Epsom salts and reacted them at a range of temperatures. Students observed a trend consistent with the Arrhenius equation and collision theory: the reaction time decreased as the temperature of the water increased. This experiment is ideal for first year undergraduate chemistry courses and was met with excitement and enthusiasm from the students who tested it. The experiment uses readily available and inexpensive ingredients, making it very accessible and an attractive demonstration for outreach events.

Ingredients

Each batch makes two bath bombs. One batch is:

• 30 g sodium bicarbonate (NaHCO₃, baking soda)
• 15 g citric acid
• 15 g Epsom salt
• 1-2 drops food coloring
• 2-5 drops water

Other materials

• ice
• 2 decimal place balance
• 150 mL beaker (or small cup)
• 1 L beaker (or bowl)
• 10 mL graduated cylinder
• hot plate (or stove)
• thermometer
• dropper
• watch glass
• spatula
• 2 plastic Easter eggs (to be used as a mold)

The author of this post is:

Natalie Ulrich

I’m a chemistry professor at Maryville University in St. Louis, MO. I teach general and organic chemistry, have three kids, and love to hike, fish, travel, and spend time with my family.

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