STEAM Powered Family

Fascinating Bath Bomb Science Fair Project

You know we love a good bath bomb project around here. It’s a fantastic way to explore science, and specifically chemistry, in a hands on, real life way. Kids love making bath bombs, and most of all erupting bath bombs! That fizz is irresistible. But recently we were working on some bath bombs and an interesting question came up. A question that was perfect for a Bath Bomb Science Fair Project !

BATH BOMB SCIENCE LAB

What you will discover in this article!

Bath Bomb Science Fair Project

Disclaimer: This article may contain commission or affiliate links. As an Amazon Influencer I earn from qualifying purchases. Not seeing our videos? Turn off any adblockers to ensure our video feed can be seen. Or visit our YouTube channel to see if the video has been uploaded there. We are slowly uploading our archives. Thanks!

If you have spent any time at all here on STEAM Powered Family you know we love child led inquiry. When a child has a great question, my inclination is always to listen, consider, and then work with them to find the solution. Science in particular is a fascinating field for kids and the questions lead to some amazing things!

Recently we were making some cauldron bath bombs. I had my kids helping me get some pictures and when they went to pour some water from the tap on the bath bombs…. nothing happened. A few little bubbles escaped through the water, but essentially they just sat there doing nothing.

At first we thought we had forgotten something important in our bath bomb recipe, but then we had an idea, what if the water wasn’t warm enough?

Sure enough, we used hot water the second time around and those bath bomb cauldrons fizzed like crazy!

We looked at each other, our eyes glimmering with excitement. We knew we had just uncovered something really cool.

My kid marched out of the room, hand in the air announcing, “Science time!”

Bath Bomb Science Fair Video

Check out the video we took of our experiment. The results are so fun!

Bath Bomb Science Experiment

Bath Bomb Science Fair Project

Bath Bomb science time didn’t happen that day, but we did start discussing how we should do our investigation. We used the scientific method and decided to set it up just like a Science Fair project .

Topic Question

We obviously had our topic and our question came easily: How does water temperature affect the fizz and eruption of bath bombs?

We did a bit of research, but from our previous heat transfer projects we had an idea about how temperature might be impacting the eruptions. Plus of course we had already done a little preliminary testing!

Our hypothesis was that temperature would have a dramatic impact in how quickly a bath bomb fizzed. We felt the best way to measure this would be to time the bath bombs to see how long they would take to completely finish erupting.

Bath Bomb Science Experiment

For our experiment we started by making bath bombs. We made a large batch of small bath bombs, so we could weight the final products once they set up, and make sure we picked ones that were very close in size.

Get some great bath bomb recipes for kids here .

You could definitely use store bought bath bombs for this project, simply make sure you buy the same types to ensure your constant.

Once we had our bath bombs, we filled three mason jars with water. One was cold from the fridge, one was warm from the tap (approximately what we estimated bath water would be), and the other was fairly freshly boiled from the kettle.

Using a digital thermometer we took the temperature of each jar of water.

Then on the count of three we dropped one bath bomb into each mason jar at the same time.

The result was spectacular! And far more impressive, and messy, than we expected. We actually had to abort the test and set up again using a casserole dish to catch the mess the second time.

Results of bath bomb science experiment

Evaluate & Draw Conclusion

It was very easy to see what a difference temperature made on the bath bomb eruption. The hot immediately fizzed and overflowed everywhere! The luke warm water fizzed slowly and lasted a long time. Hitting full foamy fizz, and overflowing a bit, after a few minutes. The cold water barely did anything with only a few bubbles escaping every once and a while.

Another thing we noted was that once the reaction died down, the amount of water lost varied significantly between the jars.

results of bath bomb experiment

Bath Bomb Science

So what is going on? The science behind this is quite simple, and something we have explored a lot in various Heat Transfer activities , Bottle Crush is a fantastic example of this concept. The hotter the water the more energy it has. Higher temperature means more energy.

Heat energy is how much those water molecules are moving about, and in the almost boiling water they are moving so rapidly that when the water was boiling you get the bubbles and boiling action and visible movement in the water.

We have talked a lot in the past about why bath bombs erupt and fizz. In a nutshell, it is an acid-base reaction . When the ingredients are dry they don’t react, they need water molecules to trigger the reaction between the acid and base.

The hotter the water, the more those water molecules are moving about, triggering reactions between the acid and base, one product of this reaction is the release of CO2 gas which creates the bubbles and fizz.

Bath Bomb Science Experiment on temperature

HOW TO MAKE BATH BOMBS

Ready to try this experiment yourself? Here is how we made our bath bombs.

First, since we wanted to ensure our bath bombs had the same weight, we made two types, round ones in the standard bath bomb mold, plus some semi circle ones in a silicone mold.

EASY BATH BOMB RECIPE

2 cups baking soda 1/2 cup citric acid 1 cup cornstarch 3 tablespoons coconut oil 1 tablespoon polysorbate 80 Essential oil if desired Mica powder (if desired, we used pink) 1 large mixing bowl 1 microwave safe bowl Molds (we used 2 types)

Sodium Bicarbonate, Baking Soda, by Pure Organic Ingredients, 2 lb, Highest Purity, Food Grade, Eco-Friendly Packaging

In the large bowl mix the baking soda, citric acid and cornstarch together.

In the microwave safe bowl, melt the coconut oil until it is liquid. Add polysorbate 80, essential oils if desired and the mica powder. Mix.

Add the wet ingredients to the dry ingredients. Using your hands (wear disposable gloves to protect your hands if desired), work the mixture together until it becomes like wet sand and can be molded.

Pack the molds. My son took some video of me packing the round bath bomb molds with my preferred technique of heaping and squishing. You can watch it here .

For the silicone molds, simply pack the mix into the mold firmly but without pressing so hard that you crack the mix.

Let sit for 24 to 48 hours in a warm, dry place. For the silicone molds, I removed the bath bombs after 24 hours, then let them sit for another 24 hours.

You are now ready for science! Make sure you store your bath bombs in an airtight container until you are ready to conduct the experiment.

We had a lot of fun with this bath bomb science fair project! It also gave us some ideas for future experiments using bath bombs. Those will be coming soon!

Bath Bomb Science Fair Project

Join the Newsletter and get a free STEAM Fun Pack plus access to many more educational resources and products.

hypothesis on bath bombs

SCIENCE FAIR PROJECT IDEAS AND RESOURCES

Science Fair ideas for elementary

5 Days of Smart STEM Ideas for Kids

Get started in STEM with easy, engaging activities.

The Science of Bath Bombs (and How to Make Them)

bath bomb

When the weather outside is frightful, soaking in a hot bath can sound especially appealing. And adding a bath bomb to the water can elevate the experience. But what exactly is in these scented spheres, and what makes them so fizzy?

Bath bombs are usually made from three key ingredients: baking soda, citric acid and cornstarch, said Frankie Wood-Black, an instructor in chemistry at Northern Oklahoma College and an experienced bath-bomb maker. Often, bath bombs also include dyes and perfumes, and sometimes they have epsom salt .

The fizziness of bath bombs comes from the chemical reactions that happen when the baking soda and citric acid come into contact with water, Wood-Black told Live Science. Baking soda, or sodium bicarbonate, has the chemical formula NaHCO3. In water, baking soda quickly dissolves, and the positively charged sodium (Na+) breaks apart from negatively charged bicarbonate (HCO3-). [ Goopy Science: How to Make Slime with Glue ]

Meanwhile, the citric acid also dissolves, with a single hydrogen ion (H+) separating from the rest of the molecule, Wood-Black said. Then, that positively charged hydrogen from the citric acid and the negatively charged bicarbonate from the baking soda mingle, very quickly undergoing a series of reactions. One of the end products is carbon dioxide (CO2). Because carbon dioxide is a gas, it forms small bubbles in the bath water, creating a delightful fizz.

If there are perfumes or scented oils in the bath bomb, they are released into the air with the carbon dioxide bubbles, Wood-Black said. The sodium from the baking soda and the rest of the citric acid molecule (minus the hydrogen that it lost when it dissolved) simply remain in the water.

The cornstarch in a bath bomb has just one job: It slows down the reaction.

By binding to the baking soda as well as the citric acid, the cornstarch slows down the rate at which both of them dissolve. The effect is that the fizziness may last 3 or 4 minutes, instead of only seconds, Wood-Black said.

Making bath bombs is not difficult, she said. She mixes 1 cup of baking soda, one-half cup of citric acid and one-half cup of cornstarch together in a bowl. All three items can be found at grocery stores. Citric acid is found in soda and candy and can also be used to make cheese, Wood-Black noted. After mixing the three ingredients, she adds about 1 teaspoon of water, which is enough to just barely moisten the ingredient mixture so that the powder sticks together. She then scoops the mixture into a mold (such as a Santa or a star candy mold) to form a shape and lets the shapes dry overnight.

But you can also just mix together the three key ingredients and skip the water. Leave the mixture in a jar, and then scoop it into your bath, she said.

Food coloring can be used to dye bath bombs, she said. But she doesn't dye the ones she makes. "I opt not [to do that]," she said. "I'm a chemist by profession, but with food coloring, I just get it all over the place."

  • How to Make Oobleck - A Simple Recipe for Making Slime
  • How to Make Puffy Slime
  • Frozen Family Fun: Try These Cold-Weather Science Experiments

Originally published on Live Science .

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Karen Rowan

'This is weird': Experts 'shocked' by record-breaking longevity of Death Valley's phantom lake

'More unzipping of the landscape': Arctic permafrost could crumble into rivers, unleashing devastating feedback loop

James Webb telescope finds ancient galaxy larger than our Milky Way, and it's threatening to upend cosmology

Most Popular

By Emily Cooke February 20, 2024

By Keumars Afifi-Sabet February 20, 2024

By Ben Turner February 19, 2024

By Emily Cooke February 19, 2024

By Harry Baker February 19, 2024

By Elyse Hauser February 19, 2024

By Keumars Afifi-Sabet February 19, 2024

By Nancy S. Jecker, Andrew Ko February 19, 2024

By Nicoletta Lanese February 19, 2024

By Victoria Atkinson February 19, 2024

By Kristina Killgrove February 18, 2024

  • 2 Ancient rock art in Argentinian cave may have transmitted information across 100 generations
  • 3 Stunning rock art site reveals that humans settled the Colombian Amazon 13,000 years ago
  • 4 There's an asteroid out there worth $100,000 quadrillion. Why haven't we mined it?
  • 5 1,800-year-old Roman tombs in Bulgaria included medallion featuring an emperor and glass bottles for collecting mourners' tears
  • 2 Why don't humans have gills?
  • 3 There may be a 'dark mirror' universe within ours where atoms failed to form, new study suggests
  • 4 1,800-year-old Roman tombs in Bulgaria included medallion featuring an emperor and glass bottles for collecting mourners' tears
  • 5 April 8 total solar eclipse: Why this eclipse repeats itself every 54 years

How Do Bath Bombs Work? The Science

lush-golden-wonder

Bath bombs are awesome balls of fizzy goodness, with some interesting science behind them! They were invented in 1989 by Mo Constantine, one of Lush’s founders. Bath bombs contain the chemical sodium bicarbonate, also known as baking soda, as their key ingredient.

This is the text version – scroll down for the video!

Some of you might remember that baking soda isn’t good for your skin because it’s a base, with a high pH. High pH (alkaline or basic) products disturb the skin’s acid mantle, which protects your living tissue from the environment, particularly bacteria, like acne-causing Propionibacterium acnes .

But don’t fret! The second key ingredient in a bath bomb is a solid acid, such as citric acid or tartaric acid (cream of tartar). This lowers the pH by reacting with the baking soda when water is added to the mixture. Unless the maker of the bath bombs has really messed up their proportions, the final pH should be reasonably neutral. Until the water dissolves the acid and baking soda and allows them to mix at a microscopic level, nothing happens.

Aside from neutralisation, the acid + base reaction with sodium carbonate also produces tiny bubbles of carbon dioxide gas, which is what causes the fizzing:

Citric acid + sodium bicarbonate → sodium citrate + water + carbon dioxide

C 6 H 8 O 7 (s) + 2NaHCO 3(s)  → Na 2 C 6 H 6 O 7(aq) + 2H 2 O (l) + 2CO 2 (g)

This is almost the same reaction as the one commonly used in volcano science projects to create foaming “lava” (they usually use vinegar as the acid). Of course, in bath bombs, there’s also fragrance and colours and glitter – the fizzing helps the bath bomb disperse faster, and combined with heat from the hot water, spreads the scent faster and makes the whole bathroom smell amazing.

lush-bath-bomb

Bath bombs can slowly absorb water from the air, using up the acid and sodium carbonate and releasing carbon dioxide prematurely – this is why bath bombs get less fizzy as they get old! Make sure you keep your bath bombs in a dry place until you’re ready to use them.

Happy bathing!

Check out the video here.

Skincare Guide

Related Posts

Make Your Own Soap! Part 2: Let’s Make Some Soap!

Make Your Own Soap! Part 2: Let’s Make Some Soap!

Nivea Daily Essentials Refreshing Cleansing Mousse

Nivea Daily Essentials Refreshing Cleansing Mousse

Reviewing Pharrell Williams’ Skincare Routine

Reviewing Pharrell Williams’ Skincare Routine

How to Mix an Aztec Clay Mask Without the Smell

How to Mix an Aztec Clay Mask Without the Smell

13 thoughts on “How Do Bath Bombs Work? The Science”

Very cool, now I do t have to look it up! Thanks 🙂

*don’t

Thanks for this article Michelle, I haven’t tried any of them yet, neither for bath not nails 🙂

Hi Michelle,

Great post. I use products from Lush daily and a Lush bomb weekly and I never thought to find out exactly why they work as they do. I love both the golden wonder bath bomb and the snow angel bath melt, I wish they were a regular, not just a seasonal Lush product. Regards Aimee 🙂 http://www.laughinggalah.com/

I love Golden Wonder too! The stars and the blue colour and the random bobbing colours are magical.

I love making bath fizzles. Thanks for the article Michele!

According to this reaction: C6H8O7(s) + 3NaHCO3(s) → Na3C6H5O7(aq) + 3H2O(l) + 3CO2(g) sodium and citric acid should be added in molar ratio of 1,3:1 (252 g sodium: 192 g citric acid). So my question is: why the proportion in your recipe is 2:1?

Thanks for pointing that out, I didn’t catch it the first time! Full neutralisation isn’t really necessary for this reaction to go – a 2:1 ratio will just produce the C 6 H 6 O 7 2- ion instead. It also has the advantage that it’s a weaker base, so the final pH will be closer to the skin’s. The equation would instead be

C 6 H 8 O 7 (s) + 2NaHCO 3(s) → Na 2 C 6 H 6 O 7(aq) + 2H 2 O (l) + 2CO 2 (g)

I’ve corrected it now 🙂

I was just going to mention this 🙂 Most bath bombs use a 2:1 ratio – some have even high citric acid if the goal is spinning/mega fizz. So the water will be acidic. Some bath bombs and other products have products that are buffers or water softeners so those will be neutralish.

awesome article! I am doing a science project on bath bombs for a 7th-grade science fair. Do you know the place of publication and publisher for this article/your website? Thank you!

Hi! I think I replied to you on IG already, but the publisher would just be Lab Muffin 🙂

HI, Michelle! how would I cite your website! I can’t seem to find you last name anywhere so it is kind of difficult to cite! Thank you!

Sorry! My last name is Wong 🙂

Leave a Comment Cancel reply

May 8, 2014

Sudsy Science: Creating Homemade Bath Bombs

By Science Buddies

Key concepts Chemistry Chemical reaction Acids Bases Water   Introduction Have you ever had a refreshing bath with bubbles or bath salts? What if you could use chemistry to create a bath-time treat that incorporated both fizzing bubbles and soothing salts? Such a combination does exist, and it's called a bath bomb. If you have never experienced one, these "bombs" become fizzy when they touch the water. Why? It is due to a chemical reaction taking place between different ingredients within the bath bomb. In this activity you'll get to make your own homemade bath bombs and explore how changing the ratio of the ingredients affects how much the bath bomb fizzes when it comes into contact with water. Then you can use your perfected method to make some bath bombs as a gift for Mother's Day!   Background Bath bombs can have a wide range of ingredients, including bath salts (which can help sooth muscles), food coloring, fragrances and other components. There are, however, a few key ingredients that most homemade recipes have: baking soda and citric acid. Why is this? When baking soda and citric acid are mixed and are then put in water, they undergo a chemical reaction. The reaction produces lots of bubbles, which you see as the bath bomb dissolves in the water. These bubbles that make the water become so fizzy are made of carbon dioxide gas.   Another ingredient that is often used in homemade bath bombs is cornstarch. This ingredient can act as a dry "filler" that gets mixed in with the reactive baking soda and citric acid in the bath bombs. In this activity you'll explore how changing the amount of cornstarch filler affects how fizzy the bath bombs turn out and you'll figure out what goes into making the most impressive bath bomb.   Materials

  • Citric acid (This is usually available at grocery stores in the canning section.)
  • Baking soda
  • Measuring spoons
  • Vegetable oil
  • Food coloring (at least two different colors)
  • Medicine dropper
  • Forks and spoons for mixing
  • Optional ingredients to add to your bath bombs: Epsom salts and fragrance (such as essential oils).
  • A muffin tray or ice cube tray (If you are using a muffin tray, you can dry the bath bombs for 45 minutes in an oven or overnight at room temperature. If you live in a very humid environment, it's recommended to oven dry the bath bombs. If you use an ice cube tray, however, you can only dry the bath bombs overnight at room temperature.)
  • A bathtub to make a hot bath and test your bath bombs in

Preparation

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

  • If you are using a muffin tray, preheat the oven to 170 degrees Fahrenheit (or its lowest setting). Always have an adult help when using the oven.
  • Note that the recipe amounts given in this activity are for approximately filling one muffin cup, or about three ice cube cups, but this greatly depends on the exact size of the cups in your muffin or ice cube tray. If you want to make additional bath bombs, you can double or triple the recipes.
  • In one bowl mix one and one third tablespoons (tbsps.) of citric acid, two and two thirds tbsps. of baking soda and two tbsps. of cornstarch. If you are using Epsom salts, you can also add two teaspoons (tsps.) to the mix.
  • In a second bowl mix one tsp. of vegetable oil, one tsp. of water and two drops of food coloring. If you want to include fragrance, also add 15 drops into the mixture. Be sure to rinse and clean the medicine dropper and measuring spoons in between measuring the different ingredients.
  • Using a clean medicine dropper, add a few drops of the wet mixture to the dry ingredients in the first bowl. What happens when you add a drop of the wet mixture? You should see it fizz—this is the bath bomb reaction taking place! Because you don't want the bath bombs to react yet, quickly press down on the fizzy spot with the back of a clean spoon. This should stop the fizziness. Mix in the damp spot with the rest of the ingredients in the bowl. Repeat this process until you have added, and thoroughly mixed in, all of the wet ingredients (a few drops at a time) to the dry ingredients.
  • Tip: Part of the challenge of making homemade bath bombs is adding the right amount of wet ingredients. If you live in a humid environment, you may not need to add all of the wet ingredients. If the bath bomb mixture appears to continue to puff up even after you have thoroughly mixed in some wet ingredients, then the mixture may be too wet. If this happens, start over making the bath bombs from the beginning, but this time use less water in the recipe. If you find that this first recipe works better using less water, adjust the following bath bomb recipe similarly.
  • Use a clean medicine dropper to drop one drop of vegetable oil into each cup on the tray that you will be using. Then use a finger to spread the oil all around each cup's surface.
  • Fill one of the tray's cups with the bath bomb mixture. Add a spoonful at a time and use the back of the spoon and/or the palm of your hand to press the mixture down into the cup continually as the mixture is added to the cup. If you are filling multiple cups, evenly divide up the mixture between them.
  • In a third bowl combine one tbsp. of citric acid, two tbsps. of baking soda and three tbsps. of cornstarch. If you are using Epsom salts, add in two tsps.
  • In a fourth bowl mix one tsp. of vegetable oil, two and one half tsps. of water and two drops of a different food coloring. If you want to include fragrance, also add 15 drops. Be sure to rinse and clean the medicine dropper and measuring spoons in between measuring the different ingredients.
  • Use a clean medicine dropper to slowly mix the wet mixture with the dry ingredients in the third bowl, one drop at a time, as you did before, using the spoon to press down on fizzy spots and continually stir the mixture. Fill the tray's cups as similarly as possible to how you filled them for the first bath bomb recipe.
  • Let the bath bombs dry. If you are using a muffin tray, dry the bombs overnight or turn off the oven (which was preheated to 170 degrees F) and let them stay in the (turned off) oven for 45 minutes with the oven door closed. If you are using a plastic ice cube tray, dry the bath bombs overnight at room temperature. Once the bath bombs have dried, carefully remove them from the cups.
  • Tip: If the bath bombs are very crumbly, the recipes may not have had enough water in them. To fix this, you can remake the bath bombs but try using a little more water.
  • Get ready to toss the bath bombs into a bath! Fill a tub with hot (but not scalding) bathwater. Then place the bath bombs in the tub. What happens when the bath bombs are placed in the water? Is a bath bomb made from one recipe fizzier than a bath bomb made from the other recipe? Does one take longer to dissolve than the other one? Which do you think worked best? How do you think the amount of cornstarch in the recipes is related to your results?
  • Extra: In this activity you tested your bath bombs in hot bathwater, but they might behave differently in colder water. You could use a stopwatch or timer to see how long they take to dissolve in hot water and then compare it with placing them in cold water. Do the bath bombs take a different amount of time to dissolve depending on water temperature?
  • Extra: Instead of citric acid, you could experiment with making bath bombs using citric acid substitutes, such as cream of tartar or lemon juice. How do bath bombs made using a citric acid substitute compare with those made using citric acid?
  • Extra: In this activity you tried varying the amount of cornstarch but you could try making bath bombs without any cornstarch. If bath bombs are made that don't have cornstarch, how do they compare with those made with cornstarch? Are they very different?

 [break] Observations and results Did the bath bomb made using more cornstarch (following the second recipe) take longer to dissolve than the one made with less cornstarch (following the first recipe)? Did the one made with less cornstarch fizz more?   When a bath bomb comes in contact with water, the baking soda and citric acid react to make carbon dioxide bubbles. This is an acid–base reaction, where baking soda (also called sodium bicarbonate) is a weak base and citric acid is a weak acid. The cornstarch acts as a "filler" to control the reaction between the baking soda and citric acid. In this activity the second recipe used more cornstarch, and less baking soda and citric acid, compared with the first recipe. Consequently, you should have seen that a bath bomb made using the first recipe produced more vigorous bubbles and impressive fizzing, and dissolved much faster, compared with a bath bomb made using the second recipe. (The size of the bath bombs also affects how long it takes them to dissolve, because larger bath bombs will typically take longer than smaller ones to dissolve. But because the bombs from the different recipes should have been similar in size, this factor should not have greatly affected the comparison.)   Cleanup If you have extra bath bombs and want to save them for later, put them in a sealable plastic bag. Once you've settled on your favorite recipe, you can also make them and give them out as gifts!   More to explore What's New, CO2? Get to Know a Chemical Reaction ( pdf ), from the American Chemical Society Try This: A Chilling Recipe , from the Commonwealth Scientific and Industrial Research Organization Fun, Science Activities for You and Your Family , from Science Buddies Shimmy, Shimmy Soda Pop: Develop Your Own Soda Pop Recipe , from Science Buddies  

This activity brought to you in partnership with Science Buddies

Your browser is not supported

Sorry but it looks as if your browser is out of date. To get the best experience using our site we recommend that you upgrade or switch browsers.

Find a solution

  • Skip to main content
  • Skip to navigation

hypothesis on bath bombs

  • Back to parent navigation item
  • Find resources
  • Experiments and investigations
  • Cross-curricular activities
  • Meet the scientists
  • Boost your knowledge
  • Beyond the classroom
  • Get funding
  • About the RSC

Hands mixing cornflower and water with green food colouring

  • More from navigation items

From kitchen to classroom

  • 1 Introduction
  • 2 Separation techniques
  • 3 Red cabbage rainbows
  • 4 Making bath bombs
  • 5 How to make butter
  • 6 Tricking taste buds with toothpaste
  • 7 Kitchen roll chromatography
  • 8 Investigating surface tension with milk
  • 9 Chalky spinach
  • 10 How to purify water

Making bath bombs

Learn how to make fizzing bath bombs by mixing an acid and an alkali

Did you know you can make bath bombs using ingredients you can find in your kitchen?

In this video, RSC education coordinator Catherine shows how to make fun fizzing bath bombs by making a mixture of an acid and an alkali, explaining the reaction when they are dropped into a bath. This simple activity can be set for learners to try at home with a responsible adult or used as a classroom experiment.

Equipment list

  • A tablespoon
  • Ice cube tray, or something to shape the bath bombs
  • Bicarbonate of soda
  • Citric acid powder or cream of tartar
  • A small amount of water
  • Food colouring (optional)
  • Essential oils (optional)

Health and safety

  • Make sure that you thoroughly clean any equipment before using for food.
  • Consider any possible allergies before undertaking the experiment.

Activity instructions

  • In one bowl, mix together two tablespoons of bicarbonate of soda with one tablespoon of citric acid or cream of tartar.
  • In the other bowl, mix together a tablespoon of water and 3-4 drops of food colouring and essential oils (this step is optional).
  • Tip the dry ingredients into the bowl with the wet ingredients and thoroughly mix together until combined. The result may still be a little crumbly but will stick together when pressed.
  • Shape the mixture into the mould you’re using and press down firmly to ensure the mixture sticks together. These quantities will make two small bath bombs.
  • Leave overnight, then the bath bombs can be eased out of the mould and placed into a tub or bath of water to watch the reaction.

Explanation

When an acid and an alkali react together, a gas is produced. This can be demonstrated by combining an acid and an alkali and observing that there is no reaction while the ingredients are dry. However, when dropped into water the bath bomb dissolves and a chemical reaction occurs and a gas can be seen fizzing from the bath bomb – in this case the gas is carbon dioxide. This experiment also shows how materials change and is an example of a non-reversible reaction.

Also check out

  • More simple experiments using everyday equipment which your learners can try at home or you can bring to the classroom on our  YouTube playlist .
  • Read the CLEAPSS guidance on practical activities for pupils at home during extended periods of school closure,  GL339 .
  • Read the SSERC guidance for  primary home learning .

Making bath bombs teacher notes

Making bath bombs handout.

Young girl dying water different colours

Introduction

Picture of a modern kitchen

Separation techniques

Picture of chopped red cabbage

Red cabbage rainbows

Picture of an orange bath bomb fizzing under water

How to make butter

Glass of orange juice

Tricking taste buds with toothpaste

Picture of kitchen roll

Kitchen roll chromatography

Picture of swirling patterns of food colouring in milk

Investigating surface tension with milk

Picture of fresh spinach leaves

Chalky spinach

Picture of a glass of water in a desert

How to purify water

  • Practical experiments
  • Acids and bases
  • Practical skills and safety
  • Observing and measuring
  • Reactions and synthesis

Specification

  • 8. Investigate reactions between acids and bases; use indicators and the pH scale
  • Acids, bases and salts. Neutralisation - formation of a salt from an acid and a base.
  • cii) neutralisation as the reaction of: ii) acids with bases, including carbonates, metal oxides and alkalis (water-soluble bases), to form salts, including full equations
  • C5.4.4 describe neutralisation as acid reacting with alkali to form a salt plus water including the common laboratory acids hydrochloric acid, nitric acid and sulfuric acid and the common alkalis, the hydroxides of sodium, potassium and calcium
  • C5.3.3 describe neutralisation as acid reacting with alkali to form a salt plus water including the common laboratory acids hydrochloric acid, nitric acid and sulfuric acid and the common alkalis, the hydroxides of sodium, potassium and calcium
  • C3.3d describe neutralisation as acid reacting with alkali or a base to form a salt plus water
  • A neutralisation reaction is one in which a base reacts with an acid to form water. A salt is also formed in this reaction.
  • a metal carbonate + an acid → a salt + water + carbon dioxide

Related articles

A photo of a test tube of a clear liquid containing with brown-edged blue liquid blobs. The test tube is also submerged in a clear liquid.

Demonstrate concentration and density with a transition metal colloid cell

2024-02-19T10:06:00Z By Declan Fleming

Boost 11–14 learners’ understanding of diffusion and transition metal chemistry

Paracetamol book | The extraction and purification of paracetamol from tablets

How pure is paracetamol? This practical lets learners distil and tablets and answer that very question.

q2

Paracetamol book | The formation of an amide

Explore the formation of an amide with this practical experiment suitable for learners ages 16-18

1 Reader's comment

Only registered users can comment on this article., more from primary science.

A photo of students doing an experiment in a school lab

Catherine’s chemistry practical skills sessions

Find out how Catherine organised her chemistry practical skills sessions and get tips for applying to the RSC Primary Science Teaching Empowerment Fund

The Primary Science Teaching Trust (PSTT) logo, featuring a segmented, multicoloured circle, against a white background

CPD support from the Primary Science Teaching Trust

Explore professional development resources, webinars and support from the Primary Science Teaching Trust.

Six pictures of various scientists carrying out their job roles

STEM careers and skills activities

Five out of five

Introduce primary learners to STEM careers and encourage them to explore their own skills. Includes a game, colouring poster, fact files and teaching notes.

  • Newsletters
  • Find your local education coordinator

Site powered by Webvision Cloud

  • Earth Science
  • Physics & Engineering
  • Science Kits
  • Microscopes
  • Science Curriculum and Kits
  • About Home Science Tools

Science Projects > Chemistry Projects > How To Make a Fizzy Bath Bomb Reaction  

How To Make a Fizzy Bath Bomb Reaction

Some bath products fizz and make bubbles when added to water.

Ever wonder why?

Discover how fizzy bath bombs can not only invigorate your bath time but your science lessons, as well!

With this easy spa science project, you’ll first make your own fizzy bath bombs, then experiment with them to discover acid-base chemical reactions. (Adult supervision recommended.)

hypothesis on bath bombs

What You Need:

  • 1/2 cup baking soda
  • 1/4 cup citric acid in powder form
  • 1/4 cup cornstarch
  • 2-1/5 tablespoons Epsom salts
  • 1-1/4 tablespoons olive or almond oil
  • 1-3/4 teaspoons water
  • 1/4 teaspoon fragrance oils
  • 1/8 teaspoon borax
  • Plastic mixing bowl
  • Jar with lid or other airtight container
  • Molds* or ice cube trays

What You Do:

mix fizzy bath bombs

1. Put the gloves on and combine the baking soda, citric acid, corn starch, and Epsom salts together in a bowl. Mix well and set aside.

2. Combine the oils, water, and borax in a jar. Cover it with the lid and shake vigorously to mix the ingredients well.

3. Slowly add the liquid mixture to the dry mixture, a few drops at at time, stirring continuously and quickly to minimize fizzing. When fully mixed, the mixture will be very dry and crumbly.

hypothesis on bath bombs

4. Pack the mixture into molds or ice cube trays and let rest for two days. *We used the Bath Bomb Science Kit , which contains the non-household ingredients you need—including the molds shown here—in the amounts you need.

hypothesis on bath bombs

5. After two days, carefully remove the mixture from the molds. 

6. Take one of the finished bath bombs and drop it in water. What happens?

What Happened:

Bath fizzies, fizzy bath bombs, effervescent bath bombs—no matter what you call them, fizzy bath bombs are a bath time treat that shows how acids and bases react when mixed together.

In this fizzy bath bomb science project, the baking soda is the base and the citric acid is, well, the acid. But the chemical reaction of this acid-base combination can be controlled by the other ingredients in the bath bomb.

The cornstarch and Epsom salts in the bath bombs both act as liquid absorbers to help keep the baking soda and citric acid from reacting with each other when liquids are added.

They are also helpful if you live somewhere with high humidity. The borax acts as both a preservative and an emulsifier, stabilizing the acid and the base within the bath fizzies.

It helps prevent them from reacting with each other before entering the water. If that effervescent reaction happened before they hit the bath, you’d have quite a mess!

Water is the catalyst  that causes the reaction to occur. It dissolves the solids and allows the ions in the acid and the base to move and collide with each other, causing a chemical reaction.

A catalyst is something added to a chemical mixture that speeds up the chemical reaction time. This reaction forms carbon dioxide, a gas, which rises to the surface of the bathwater in the form of bubbles.

The oils and the fragrances are useful as a liquid to help form the fizzy bath bombs as well as leave the skin smooth and scented.

To make this spa science project even simpler, download a free fizzy bath bomb printable here. And check out the complete fizzy bath bomb science kit .

Click Here to Download

For further study , try these other fun spa science projects:

  • Homemade Bath Salts
  • DIY Sugar Scrub
  • Natural Lip Balm

Welcome! Read other Chemistry articles or explore the rest of the Resource Center, which consists of hundreds of free science articles!

Shop for Chemistry Supplies!

Home Science tools offers a wide variety of Chemistry products and kits. Find affordable beakers, test tubes, chemicals, kits, and everything else you need for lab experiments.

Related Articles

Thanksgiving Science Projects eBook

Thanksgiving Science Projects eBook

Fun & Easy Science Activities Your Kids Will Love!

Weekly Lesson Plan Sheet for Homeschool Science

Weekly Lesson Plan Sheet for Homeschool Science

Want to make planning your children’s homeschool science school calendar simple? Who doesn’t? We created this handy planning worksheet you can use for any student, K-12 to make lesson planning easier and faster.

K-12 Science Curriculum Guide

K-12 Science Curriculum Guide

Selecting a science curriculum that’s a good fit for you and your students is the first step toward a great science learning experience. Because every teacher-student situation is different, there is no one science curriculum that is best for every homeschool family....

Best Homeschool Science Curriculum

Best Homeschool Science Curriculum

Every year most homeschool families go through the difficult process of deciding what curriculum to use for the next year.

10 Science Experiments You Want To Do This Year

10 Science Experiments You Want To Do This Year

Science experiments are one of the most fun things you will get to do in your homeschool or classroom! You’re not only learning and applying knowledge — you’re also having fun! I've put together some really fun and easy science experiments for you and your family to...

JOIN OUR COMMUNITY

Get project ideas and special offers delivered to your inbox.

should I learn computer coding

  • Science & Math
  • Sociology & Philosophy
  • Law & Politics

The Effect of Temperature on Hydrochloric Acid and Bath Bombs to Produce Carbon Dioxide Lab Answers

  • The Effect of Temperature on…

INTRODUCTION:

Bath bombs consist of a wide range of ingredients, including bath salts, food coloring, fragrance, citric acid, sodium carbonate, and other components. Bath bombs ‘fizz’ when water inclines to trigger a reaction between an acid and a base (neutralizing substance). Many bath bombs contain citric acid, and sodium carbonate, which incline to have a weak base. This reaction helps to break up the bath bomb, releasing fragrances, detergents, and oils. Furthermore, when a bath bomb contacts with water, the sodium carbonate, and citric acid react to make carbon dioxide bubbles and gas that defines the product. This is an example of a chemical reaction. The kinetic energy associated with particles increases or decreases with temperature. As such the more energy produced within a practical, the more It bounces. The more it bounces around, the more likely it will collide with other particles. Therefore, for this reason, the rate of reaction hugely increases the temperature. However, as a contrast, it does also decrease the temperature.

AIM:   To investigate how temperature affects the reaction of hydrochloric acid and bath bombs to produce carbon dioxide.

HYPOTHESIS:   The higher the temperature, the greater volume of carbon dioxide produced.

Independent Variable: Temperature ( C)

Dependent Variable:  Volume of Carbon Dioxide (cm). Carbon Dioxide is measured through the use of a balloon and string. After the balloon is filled up with carbon dioxide after a minute, the string is used to check the diameter of the balloon in cm. 

Controlled Variables :

  • 25ml Measuring Cylinder 
  • 3x petri dishes
  • 3x plastic tubs
  • Hot water & Room temp water
  • Ice  
  • 15 grams bath bombs 
  • 6x balloons 
  • Stopwatch 
  • String 
  • Measuring tool (i.e. ruler and kitchen scale)
  • Hydrochloric acid 1.0M (150ml total)
  • Place 1 beaker in a tub filled with ice cubes, then place another filled with hot water, finally leave the 3rd beaker as it is. 
  • Collect 25ml of 1.0 hydrochloric acid in a 25ml measuring cylinder.
  • Collect and add 5g of bath bombs into three different petri dishes.
  • Empty each petri dishes with 5g of bath bombs into all three beakers. 
  • Get a balloon and stretch the opening.
  • Pour the Hydrochloric acid from the measuring cylinder into a beaker.
  • Quickly place a balloon on top of the beaker, making sure the gas does not escape.
  • Time the reaction for a minute using a stopwatch.
  • Measure the circumference of the balloon using a string and a ruler. 
  • Repeat steps 1-9 1 more time.

DISCUSSION:

The results derived from the experiment show that the average balloon size for temperatures like iced inclined to 19, room was 19 and hot was 18.25. These results however incline to highly differentiate from the expected results. As the particle theory states that as temperature increases, the particles in a reaction then have more kinetic energy, which in turn causes them to move faster and collide more. Hence, this should usually mean that the width of the balloon in the hot water tub should incline to be greater than the balloons in ice and room temperature, due to there being fewer collisions happening because of lower temperatures the breakers are placed in. The inconsistencies could be due to various random and systematic errors being present.

EVALUATION:

Random errors- As the number of random errors increases the reliability decreases and vice versa. 

It is important to repeat the experiment after noting the systematic errors, since it inclines to then help provide more accurate results, knowing that they won’t occur again.

CONCLUSION:

The aim of this practical is to determine the effect of temperature on hydrochloric acid and bath bombs to produce carbon dioxide. The findings inclined to highly vary from the hypothesis. This was due to all temperatures producing the same averages. The contrast of results derived might be due to the random and systematic errors.

BIBLIOGRAPHY:

Davies, E 2018,  What causes bath bombs to fizz? , BBC Science Focus Magazine, BBC Science Focus Magazine, viewed 25 November 2021, <https://www.sciencefocus.com/science/what-causes-bath-bombs-to-fizz/>.

Science Buddies 2014,  Sudsy Science: Creating Homemade Bath Bombs , Scientific American, viewed 25 November 2021, <https://www.scientificamerican.com/article/sudsy-science-creating-homemade-bath-bombs/>.

Related Posts

  • Glucose & Sucrose Fermentation: Carbon Dioxide Production Lab Answers
  • The Carbon Cycle
  • What are acid/ base Indicators?

Author:  William Anderson (Schoolworkhelper Editorial Team)

Tutor and Freelance Writer. Science Teacher and Lover of Essays. Article last reviewed: 2022 | St. Rosemary Institution © 2010-2023 | Creative Commons 4.0

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

Post comment

COMMENTS

  1. Bath Bomb Science

    1 2 3 4 5 1,858 reviews Abstract Have you ever had a refreshing bath using a bath bomb? A bath bomb is several ingredients mixed and molded into a shape, which becomes fizzy when it touches the water. It can be quite a relaxing experience, especially if your bath bomb has a nice fragrance or includes some bath salts.

  2. Fascinating Bath Bomb Science Fair Project

    By Shelley Brewer Updated 31/05/2023 You know we love a good bath bomb project around here. It's a fantastic way to explore science, and specifically chemistry, in a hands on, real life way. Kids love making bath bombs, and most of all erupting bath bombs! That fizz is irresistible.

  3. The Science of Bath Bombs (and How to Make Them)

    The cornstarch in a bath bomb has just one job: It slows down the reaction. By binding to the baking soda as well as the citric acid, the cornstarch slows down the rate at which both of them...

  4. How Do Bath Bombs Work? The Science

    Citric acid + sodium bicarbonate → sodium citrate + water + carbon dioxide. This is almost the same reaction as the one commonly used in volcano science projects to create foaming "lava" (they usually use vinegar as the acid). Of course, in bath bombs, there's also fragrance and colours and glitter - the fizzing helps the bath bomb ...

  5. Sudsy Science: Creating Homemade Bath Bombs

    Background Bath bombs can have a wide range of ingredients, including bath salts (which can help sooth muscles), food coloring, fragrances and other components. There are, however, a few key...

  6. Sizzle and Fizzle of Bath Bombs: An Inexpensive and Accessible Kinetics

    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.

  7. Fizzy irreversible changes and bath bombs

    This resource is also available in Welsh and Irish. Get the Welsh language version. Get the Irish language version. This experiment focuses on how materials change when they react together. First watch the 'bath bombs' demonstration video, then find out how your learners can use similar ingredients to explore an irreversible reaction.

  8. PDF How to Produce the Most Fizz with Bath Bombs

    and citric acid in bath bomb recipes to produce the optimum amount of fizz that is released once the bath bomb touches water. It was expected that a mixture of approximately 0.76 grams of citric acid for every gram of baking soda would produce the most fizz. This hypothesis was based on the chemical reaction formula. Methods

  9. PDF Bath Bombs: How Can We Make Something New That Was Not There Before

    Lesson 5: Students argue from evidence what gas(es) could be produced by a bath bomb reaction. The class tests ^the flammability of air from the room, gas from the bath bomb, and helium gas _ (Teacher Edition, page 117). They argue from evidence that the gas from the bath bomb could be nitrogen, argon, or carbon dioxide.

  10. Making bath bombs

    Leave overnight, then the bath bombs can be eased out of the mould and placed into a tub or bath of water to watch the reaction. Explanation. When an acid and an alkali react together, a gas is produced. This can be demonstrated by combining an acid and an alkali and observing that there is no reaction while the ingredients are dry.

  11. PDF Experimental Procedure

    Making bath bombs can be significantly affected by surrounding humidity levels. i. If the bath bomb mixture ever appears to continue to puff up and fizz even after you have thoroughly mixed in some wet ingredients, then the mixture may be too wet and the bath bombs will not form properly.

  12. How to Make Fizzy Bath Bombs Science Fair Project

    How To Make a Fizzy Bath Bomb Reaction With this easy spa science project, you'll first make your own fizzy bath bombs, then experiment with them to discover acid-base chemical reactions. (Adult supervision recommended.) 1/4 cup cornstarch 2-1/5 tablespoons Epsom salts 1-1/4 tablespoons olive or almond oil 1-3/4 teaspoons water

  13. Ask an Expert: Bath bomb project question

    Our hypothesis was that the extra cornstarch recipe will do more reaction (bubbles and fizziness) but we had to declined our hypothesis. The normal recipe did a way better and impressive bath bombs reaction. Also, the extra cornstarch recipe dissolve in less time than the normal one. I just want to know if that make sense at all.

  14. BUBBLE BUBBLE Bath Bombs

    Our hypothesis is that the bath bomb with a ratio of 5:1 or 1:5 of baking soda and citric acid will bubble for a long amount of time in the same bubbling condition. This means that the bubbling may last longer but the bubbling of the bath bomb will be weaker. If one of the numbers in the ratio is extremely high or low, when the Baking soda and ...

  15. Bath Bomb Hypothesis

    Bath Bomb Hypothesis 667 Words3 Pages Developing a topic for Science Fair will never be easy unless you have a little background about that certain topic. One particular scientist is developing her topic by researching questions she has that revolved around her topic.

  16. Science Experiment with Bath Bombs

    Bath bombs are "da bomb" because they fizz in the bath and they turn the water different colors. They also smell amazing and make your skin soft from the oils. You can make them in kid shapes using sand toys and-presto-taking a bath becomes fun again (for kids AND adults!). They also make lovely gifts.

  17. The Effect of Temperature on Hydrochloric Acid and Bath Bombs to

    Many bath bombs contain citric acid, and sodium carbonate, which incline to have a weak base. This reaction helps to break up the bath bomb, releasing fragrances, detergents, and oils. Furthermore, when a bath bomb contacts with water, the sodium carbonate, and citric acid react to make carbon dioxide bubbles and gas that defines the product.

  18. Hypothesis

    Hypothesis - Bath bombers Our hypothesis is that if we increase the pH,the time it will take to fizz will increase, because of the carbon dioxide created from the chemical reaction between the citric acid in the lemon juice and the baking soda. This will cause it to fizz because having more acid means having more fizz.

  19. Does the temperature of water affect how fast a bath bomb dissolves?

    Hypothesis I think the hottest temperature of water (195) will make the bath bomb dissolve the fastest. I feel like it will make it melt sort of and then it will dissolve fast. Procedure 1....

  20. Ask an Expert: Bath Bombs Expert Interview Questions

    1. Why do the specific ingredients of bath bombs create the reaction that it does? 2. Does the temperature of the water a bath bomb is placed in impact its reaction? If so, why? 3. Do stress-relieving bath bombs have different ingredients causing different reactions? 4. Does hard and soft water create different reactions? If so, why? 5.

  21. Science Fair Note Cards Flashcards

    Hypothesis - Our hypothesis is that if the temperature of water is hotter, than the reaction time of the bath bomb will be faster, but if the temperature of the water is cooler, than the reaction time of the bath bomb will be slower. ... Variables-

  22. What to Know About Bath Bombs and Your Skin

    Here are the most common issues caused by bath bombs: Skin irritation: caused by synthetic fragrances and artificial dye can aggravate the skin, lead to redness, itching, hives, and rashes or ...

  23. What is a Bath Bomb? (with pictures)

    Fact-checked What is a Bath Bomb? A bath bomb is a delightful blend of soothing salts, fragrances, and oils compacted into a fizzy sphere that dissolves in water, transforming an ordinary bath into a spa-like experience. It's a treat for the senses, releasing colors and aromas that relax the body and uplift the mood.