Bath Bombs
Submitted By: Julie
Overview
Make a bath bomb that will bubble and fizz when you put it in the bath tub, using the concept of
acid-base neutralization reactions. The bath bomb also soothes and softens your skin.
Topic Area(s)
Age
Chemistry; acid- 8-10
base reactions
Cost
Less
than a
dollar
Time
Prep: 10 minutes
Execution: 30
minutes
Complexity
Preparation= 3
Execution= 2
Objective
Observe what
happens when
an acid and a
base react
together.
Hook
You’ll be making bombs that will bubble and fizz when you put them in your bath tub and leave your
skin nice and smooth!
Necessary Background Information
The bath bombs are a combination of baking soda (a base), citric acid (an acid) and witch
hazel. To differentiate between acids, like vinegar, and bases, like soap, people use the pH scale.
The scale ranges from 1-14; acids range from 1 to 7, with acids closest to 1 being the strongest or
most acidic. Bases range from 7 to 14, with 14 being the strongest or most basic. Neutral solutions,
like water, have a pH of 7.
An acid-base reaction occurs when an acid and a base of equal concentrations are
combined in a solution (in this case it will be the water in the tub) to produce water and a salt, two
neutral products. This is why acid-base reactions are often referred to as neutralisation reactions.
The reaction being observed in this experiment is:
H3C6H5O7 (aq) + 3 NaHCO3 (s) → 3 CO2 (g) + 3 H2O (l) + Na3C6H5O7 (aq)
The CO2 released during this reaction is in gas form, and it is the release of this gas into the water
that causes all the bubbling and fizzing noise when the bath bomb is put in the tub.
The witch hazel we add to the bath bombs is an astringent, as well as a strong anti-oxidant that is
obtained from the Witch Hazel shrub, found in many parts of North America. It is actually used a lot
by Native Americans for medicinal purposes. It can commonly be used for minor cuts and scrapes,
dry skin, sunburns, and even to fight acne. This is why the bath bombs we are making not only
bubble and fizz, but also soothe and soften the skin.
Materials
For two people (one group):
 1 tsp citric acid
 2 tsp baking soda
 Witch Hazel squirt bottle
 Food colouring for desired colour
 A Wendy’s or McDonald’s cup
 Two popsicle sticks
 An ice tray to make the shape of the bath bombs (can be used for more than one group)
 2 small Ziploc bags (to bring the bath bombs home)
Safety Considerations
Do not put any of the materials used or the final bath bomb in your mouth, even if it looks like it
might taste good.
Procedure
1.
2.
3.
4.
5.
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7.
8.
Mix the citric acid and the baking soda in the cup, using the popsicle stick.
Lightly sprinkle the mixture with a few drops of witch hazel.
Add a few drops of the desired food colouring.
Mix well, again using the popsicle stick, until the mixture’s consistency lets you make
little balls. DO NOT OVER WORK THE MIXTURE!
Scoop a clump of the mix into the ice tray, enough to fill it just about to the top.
Continue putting the mixture into the ice tray until you’ve used all of it.
Leave bath bombs to dry.
Once dry, you can take them home with you and add them to your bath to see what
happens!