hypothesis on bath bombs

The Learning Hypothesis

Bath Bomb Science Experiment. What, Why & How

High School · Holidays · Middle School · Physical Science

Bath bombs are little chemistry sets in action.  Our exploration into bath bombs includes the chemistry of the fizz, the purpose of Epsom salt, and making our own.  This would make an excellent science fair project. This post contains affiliate links, you can read my full disclosure here .

IN A HURRY>>>

The chemistry of the fizz.  exploring bath bomb science..

Bath Bombs have lots of ingredients:

• baking soda
• citric acid (I use food grade so that I can use it in projects like popping candy later.)
• Epsom salts
• essential oil or fragrance
• food coloring (any color you want)

A chemical reaction caused the fizz. Think of an antacid tablet in water.

What makes bath bombs fizz?

Baking soda should always be in your science cabinet because it is cheap and can be used in so many ways.  I buy large boxes for science.  That is why I buy the large citric acid packages as well.

The citric acid and the sodium bicarbonate combine with water to form sodium citrate and carbon dioxide (and water).

C 6 H 8 O 7 +   3NaHCO 3 —> Na 3 C 6 H 5 O 7 + 3CO 2 + 3H 2 O

What are the indications that a chemical reaction has occurred? (besides the bath bomb chemical equation)

The production of gas and change in temperature.

Make sure to test your mixture before giving it to others.

Grab this download to turn this into a bath bomb lab

How does espom salt help.

The Epsom salt is MgSO4 and is broken down in the presence of water into its ionic components magnesium and sulfate (a polyatomic ion).  These are thought to be absorbed by the body and may help with muscle fatigue, but there’s more to that story.

Why would magnesium help with muscle fatigue?

By flushing out a substance known as lactic acid.  When you exercise,  the demand for energy increases.  We make energy through processes that require oxygen (preferred) and process that don’t (not preferred).  When the energy demands are really high we use both of these pathways to try to keep up with demand,  unfortunately, this results in lactic acid.

Muscle soreness causes a slow down in training for athletes and is often associated with this lactic acid, however, lactic acid is not the cause of delayed onset muscle soreness.

Ok, that’s cool – BUT WAIT

The deal is that it isn’t true.  While lactic acid is often associated with muscle fatigue and soreness in the days following heavy exercise it isn’t true.  Lactic acid is responsible for the burning sensation that occurs during heavy exercise and serves as a warning that you are pushing the limits of your muscles and fitness levels.

Cellular muscle damage causes the muscle soreness that shows up 1-3 days after heavy training.  This damage releases unknown substances into the surrounding tissue. It is possible that Epsom salts help to wash those toxins away or that the warm bath helps to relieve the muscles.

Recipes for Bath Bombs

There are thousands of recipes for making bath bombs.   This is where experimenting can be beneficial.

The basic bath bomb is in a 2:1 ratio

• 2 baking soda
• 1 citric acid
• 1 Epsom salt

Then add anything additional for scent, color, or moisturizing (olive oil, coconut oil, grapeseed oil – endless options)

You can check out more directions for bath bombs at the epsomsaltcounil.org

Bath bombs are very popular and a great handmade gift. They’re also a perfect chance for a Christmas Science Experiment (check out the other Christmas Science Experiments HERE ). Christmas Science Experiment #4 – Bath Bomb Science Experiment

Roth, Stephen M. “Why Does Lactic Acid Build Up in Muscles? And Why Does It Cause Soreness?”  Scientific American , 23 Jan. 2006, www.scientificamerican.com/article/why-does-lactic-acid-buil/.

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May 8, 2014

Sudsy Science: Creating Homemade Bath Bombs

A Mother's Day Treat from Science Buddies

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

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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.

  Procedure

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

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!

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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 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.

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.

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.

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)

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!

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SCIENCE FAIR PROJECT IDEAS AND RESOURCES

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

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.

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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
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Originally published on Live Science .

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How to Explain the Chemistry Behind Bath Bombs + Free Recipe

Interested in learning the science behind your favorite spa-day treat? I’ll explain the chemistry that’s responsible for making bath bombs that transform your tub into a tranquil spa!

This post contains affiliate links.

My daughter loves having “spa days” – where we soak our feet in a warm bathtub of water and then take turns painting each other’s nails. She’s in elementary school, so I never know what kind of wild manicure or pedicure my spa treatment will include! I’ve been wanting to add to our spa day ritual by making bath bombs, and it dawned on me that you might be interested in learning the science behind how these work!

Or maybe I’m just secretly hoping you’re interested in how these work, and that you’ll allow me to geek out over bath bomb chemistry.  Either way – here’s the science.

The Chemistry Behind Bath Bombs

Traditional bath bombs are made up of a few simple ingredients that, when submerged in water, make a fantastic chemical reaction! Here is a list of the essential ingredients used in making most bath bombs:

• Sodium bicarbonate (also known as baking soda or bicarb)
• Citric acid
• Magnesium sulfate (commonly known as Epsom salts or bath salts)
• Cornstarch or Arrowroot Powder
• Coconut Oil
• Various Essential oils (optional)

The Purpose of Baking Soda and Citric Acid in Bath Bombs

Baking soda, also known by its chemical name, sodium bicarbonate (NaHCO 3 ) or bicarb for short, is classified as a base. Citric acid (C 6 H 8 O 7 ) is classified as an acid. In their dry, powder forms, these two substances do not react.  However, put the two in water and POW – a neutralization reaction occurs!

When the baking soda reacts with the citric acid in water, three products are formed: sodium citrate (Na 3 C 6 H 5 O 7 ) which is classified as a salt, carbon dioxide gas (CO 2 ) which is responsible for the famous bath bomb “fizzing”, and water.

Here’s what the chemical reaction looks like:

NaHCO 3 + C 6 H 8 O 7 + H 2 O→ Na 3 C 6 H 5 O 7 + H 2 O + CO 2

Baking soda + citric acid + water → sodium citrate + water + carbon dioxide

Watch this video to see the chemical reaction happen. Be sure to listen for the fizzing!

The Purpose of Epsom Salts, Cornstarch, and Oil in Bath Bombs

I’ve explained the scientific purpose of baking soda and citric acid in bath bombs. But what is the purpose of epsom salt, cornstarch, and oil?

Magnesium sulfate (MgSO 4 ), better known as Epsom salts or bath salts, is commonly used to soothe sore muscles. When put in water, the salts dissolve, allowing the magnesium and sulfate ions to separate from one another and be absorbed through the skin.

The reason for using cornstarch or arrowroot powder is to act as a stabilizer for the bath bomb. The presence of this ingredient helps to slow down the rate at which the bath bomb dissolves, causing the “fizz” rate (or the reaction between the baking soda and citric acid) to decelerate. The greater the amount of cornstarch, the slower the bath bomb will dissolve and react.

Coconut oil is often used in bath bomb recipes for several reasons:

• Moisturizing: Coconut oil is an excellent moisturizer that helps to hydrate and nourish the skin. When used in bath bombs, it can help to prevent dryness and leave the skin feeling soft and smooth.
• Binding Agent: Coconut oil also acts as a binding agent that helps to hold the other ingredients together in the bath bomb mixture. This is because it is solid at room temperature and melts when heated, allowing it to create a solid structure when it cools.
• Easy to find: Coconut oil is widely available in stores and is relatively inexpensive, making it a popular choice for DIY bath bomb makers.
• Shelf Life: Coconut oil has a long shelf life, which means that bath bombs made with it can last longer than those made with other oils that can spoil more quickly.

Overall, coconut oil is a versatile and beneficial ingredient in bath bomb recipes that can help to enhance the overall experience of using a bath bomb.

Essential oils are added to bath bomb recipes for a variety of reasons, from adding a pleasant smell to the bath to aiding in moisture retention of the skin.

Understanding the chemistry behind how bath bombs work is a practical application of science and a fantastic way to engage your learners in STEM.

Reasons to Make Homemade Bath Bombs with Kids

Making bath bombs with kids is a fun and pleasant-smelling science activity. There are several reasons why you may choose to create DIY bath bombs:

• Customizable: Homemade bath bombs can be customized to suit individual preferences by using specific scents, colors, and ingredients. This means that you can create bath bombs that are tailored to your needs and preferences, such as using essential oils that you find soothing or using ingredients that are known to help with specific skin conditions.
• Cost-effective: Making bath bombs at home can be more cost-effective than buying them from a store, especially if you plan to make them in large quantities. Additionally, making them at home can save you money on shipping fees and packaging costs.
• Creative outlet: Making bath bombs can be a fun and creative hobby that allows you to experiment with different colors, scents, and textures. Who doesn’t like a hands-on chemistry activity that smells lovely?
• Science is cool: Yep – that alone is a reason to make homemade bath bombs.

Simple, DIY Vegan Bath Bomb Recipe for Kids

Here’s a simple recipe to make homemade, vegan bath bombs with kids. Be sure to check your kitchen and pantry shelves to see which ingredients you have on hand before purchasing new materials.

Ingredients to Make Simple Vegan Bath Bombs

• 1 cup baking soda
• 1/2 cup citric acid
• 1/2 cup Epsom salts
• 1/2 cup cornstarch
• 2 tbsp. coconut oil (melted)
• 2-3 drops essential oil of your choice
• Food coloring (optional)
• Metal bath bomb molds (you can also use silicone muffin cups or small plastic containers)

Bath bomb molds come in multiple sizes. They are measured by their diameter. I chose to use 2.2 inch metal bath bomb molds, which are similar in size to a clementine. You can also purchase Epsom salts scented with essential oils, which can allow you to skip the addition of 2-3 drops of additional oil.

Instructions for Simple DIY Vegan Bath Bombs

• In a large mixing bowl, combine baking soda, citric acid, Epsom salt, and cornstarch. Mix well.
• In a separate small bowl, mix melted coconut oil, essential oil, and food coloring (if using). Stir until the color is evenly distributed.
• Slowly add the liquid mixture to the dry mixture, while stirring constantly. Mix well until everything is evenly distributed.
• If the mixture is too dry, add a small amount of water (a few drops at a time) until the mixture holds together when pressed in your hand.
• Fill each half of your bath bomb mold with the mixture, pressing down firmly. If using silicone muffin cups or plastic containers, pack the mixture in firmly.
• Let the bath bombs dry for at least 24 hours before removing them from the molds.
• Store the bath bombs in an airtight container until ready to use.

That’s it! You now have homemade bath bombs that you can enjoy in your bath or gift them to a friend or family member!

Excellent Bath Bomb Kit for Kids

If you don’t want to purchase the ingredients you need to make DIY bath bombs from scratch, you can buy a simple bath bomb making kit that perfect for kids! I really like the DIY bath bomb kit from Earthy Good . 

Once I received the kit, I was immediately impressed with their attention to sustainable packaging, using seed packing paper to fill the empty spaces in the cardboard box the ingredients were shipped in, as well as the beautiful furoshiki gift-wrapping cloth that could be used to wrap the kit. The essential oils were packed in glass bottles and the form to make the bath bombs was made of tin – both materials that could easily be reused or recycled.

The instructions to make our homemade spa treat were easy to follow and my daughter and son both joined in the fun of making their own bath bombs.

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How to Make Simple, Vegan Bath Bombs

Here is a simple recipe to make vegan bath bombs at home.

• 1/2 cup Epsom salt
• Bath bomb molds (you can also use silicone muffin cups or small plastic containers)

Instructions

Bath bomb molds come in many different sizes. They are sold in various diameters. I chose to use 2.2” diameter metal bath bomb molds, which made bath bombs that were approximately the same size as a small orange. I also chose to use Epsom salts that were infused with essential oil, so I did not need to add my own. I opted to skip the addition of food coloring and chose instead to make white bath bombs.

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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.

Introduction

Separation techniques

Red cabbage rainbows

How to make butter

Tricking taste buds with toothpaste

Kitchen roll chromatography

Investigating surface tension with milk

Chalky spinach

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

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Ep66 – DIY Bath Bombs Science Project

Handouts are available below

Are you looking for a hands-on project in chemistry that allows students to build and test prototypes while also making chemistry real? I get students to do the DIY bath bombs project for just that reason. The project illustrates how science concepts – like rates of reactions – can be taught in hands-on ways. And, also requires students to build and test prototypes – which generally doesn’t happen in chemistry labs. My students enjoyed doing the lab, and best of all, it’s a fun, engaging, and hands-on way to teach students about the factors that affect reaction rate.

Episode Notes

The objective of the lab is for students to create 200ml of bubbles in exactly 15s. It’s like a 15s timer but with bubbles and bath bombs.

When testing their bath bombs, students fill a 250ml graduated cylinder with 50 ml of water; add a drop of dish soap; add the bath bomb and start the timer. When the bubbles reach the 250mL line of the graduated cylinder, stop the timer. 

Students are marked on how close they get to forming 200ml of bubbles in 15s. This requires students to speed up or slow down the reaction – by adjusting the concentration of the bath bomb (ie. ratio of citric acid, baking soda and corn starch in the bath bomb), shape or surface area of the bath bomb, or temperature of water – to either make bubbles more quickly or slowly to get to the 15s goal while adhering to some build restrictions.

Students also perform a few rounds of experimentation, which is part of the fun. I mark students on their improvements between prototypes as well as the overall performance of their final prototype.

Download the handouts below for bath bomb building instructions. By the end, your students will be bath bomb experts. 

Thanks for watching, and let’s talk science education again soon.

Handout(s): Ep66 Handouts – DIY Bath Bombs Science Project

A complete lab package of this activity is available now! Head to REAL Sc Lab – DIY Bath Bombs Project to purchase your copy today.

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Bath Bomb Experiment

December 28, 2020

A bath bomb or  bath fizzer is a mixture of an alkaline and an acid which reacts in water. This easy experiment explores what happens when acid and an alkaline mix, and can make bath-time a fun learning experience.

Scroll to the end of the post for a printable experiment card for you and your child to follow.

How to make a bath bomb

Bath bombs contain an acid and an alkaline in powder form. If not water is present they are unable to react together.

But, when water is added (like if you were to, say, drop it into a hot bath), then the acid and alkaline are able to mix and react with each other. This causes the intense fizzing reaction that you want from a bath bomb. Don’t worry its not dangerous, the fizzing is caused by bubbles of gasses released during the reaction.

Bath bombs often have perfume, scent or oils mixed in to make for a more pleasant bath experience.

Ingredients/ materials

Bath bombs usually just contain sodium bicarbonate and lemon juice or citric acid. These are (respectively) the alkaline and acid required for our experiment.

You may be able to source pure versions of these ingredients from some pharmacists, but they are both available at your regular grocery store (probably at a fraction of the cost).

Sodium bicarbonate is the main (and often only) ingredient in baking soda. Citric acid can be bought pure from some grocery stores, but is the main ingredient of fizzy lemon or orange drink crystals and bath salts. Sodium bicarbonate is E500, and citric acid may be listed as as E330 (in European countries).

Sodium bicarbonate [NaHCO 3 ] reacts with citric acid [H 8 O 7 ] in the presence of water to form sodium citrate, [Na 3 C 6 H 5 O 7 ], water [H 2 O], and carbon dioxide [CO 2 ].

Instructions/ the experiment

The ideal quantities of each of the ingredients will depend on how pure the products you managed to source are.

If both the citric acid and the bicarbonate are pure then a 1:1 ratio will probably work the best. If the baking powder contains any other ingredients (it often has rice flour or an other anti-caking agent), then you will need to adjust so there is more baking soda in the ratio. You may have try different mixtures: 1:1, 1:2, 1:3, until the most lively reaction occurs.

To make the bath bomb:

• Swirl the two dry powders together on a plate and then,
• Use clean wet hands, squeeze the powders into a ball. The moisture on your hands will react with the outer layers, which will feel funny and form a sort of outer crust or shell. (note: don’t do this if you have cuts or grazes on your hands as it will hurt). Getting the right amount moisture to make the ball ‘set’ will require a bit of trial and error!
• Once the ball has set, place it on a dry surface. Wash and dry your hands thoroughly.

Now take some water that is as hot as is comfortable for a bath, drop the ball into it, and watch what happens!

Once you have the basic recipe nailed you can try adding some aromatic cooking spices or natural oils such as lavender, vanilla or nutmeg. You can also add coloring – use food coloring drops, but only add a small amount and mix into one of the ingredients, and allow it to fully dry before adding to the other ingredient (or the chemicals will start reacting before we are ready!).

Bath Bomb Experiment Instruction Card

• 1/4 cup sodium bicarbonate
• 1/4 cup citric acid
• Ice-cream scoop (optional)

Instructions

• Mix sodium bicarbonate and citric acid together in a bowl.
• Use wet hands to squeeze the powders together into a ball shape. The moisture on your hands will react with the outer layers to form an outer crust or shell. Getting the right amount moisture to make the ball 'set' may require a bit of trial and error!
• You can use an ice-cream scoop to create a rounder ball shape if you like.

A rt W ith J enny K .

Science Experiment with Bath Bombs

Home » Projects » Science Experiment with Bath Bombs

Description

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. There are tons of recipes online, so we read about them and then sort of did our own thing. Since we were taking the experimentation road, we didn’t care too much if something went wrong (because there is value in that). We were having fun just trying things to “see what would happen if….” Our daughter loved the freedom of that as well. Some of the best things we learn are from our mistakes. I will break down the basic recipe we used and tell you some of the things we tried.

This project has extra credit! Check it out!

My daughter is 3, and a few months ago, she decided that taking a bath would be optional in our household (for her, at least). Her father and I disagreed, and the nightly bath struggle began. One day, while at the mall, she saw some bath bombs at LUSH and decided she wanted to try some. She LOVED them, and so did we. Finally, she would willingly take a bath – in fact, she wanted to take several baths daily. However, at almost $6 a pop (for the large ones), there was no way we would maintain that kind of entertainment just to have a bath.

So, we decided to try to make our own bath bombs. In the process, we discovered what a great opportunity it was to teach our daughter about experimenting, hypothesizing, and connecting to science (and saving money). “Hypothesis” is a big word for a 3-year-old, but I figured if she could learn “supercalifragilisticexpialidocious” or “John Jacob Jingleheimer Schmidt,” she could learn hypothesis – and she did. My husband is a scientist, so this was one artsy-craftsy thing he got roped into doing that he could relate to and enjoy (for at least the first 2 out of 5-6 batches).

There are tons of recipes online, so we read about them and then sort of did our own thing. Since we were taking the experimentation road, we didn’t care too much if something went wrong (because there is value in that). We were having fun just trying things to “see what would happen if….” Our daughter loved the freedom of that as well. Some of the best things we learn are from our mistakes. I will break down the basic recipe we used and tell you some of the things we tried. (Please note that links below are amazon affiliate links- see disclosure HERE ).

• Citric acid 
• Baking soda
• Corn starch
• Color (food coloring or liquid watercolor paint)
• Oil (olive, vegetable, coconut & baby oil – or any of your choice)
• Essential oils (for fragrance)
• You’ll need regular cooking supplies like measuring cups, bowls, forks, etc.
• Optional: We used Epson salts and bath pearls and experimented with bubble bath (see how that experiment went below).
• We used measuring cups to get the shape of most of our bombs and also a meatball maker for the round ones. To get the kid shapes, we used kinetic sand toy molds.

Optional: We hid small toys like spinning tops and balls in the larger bath bombs and used cupcake liners to dry our finished bath bombs in.

How to make your own Bath Bombs!

Mix Dry Ingredients:  We made big batches of the dry mixture by multiplying the basic recipe and keeping it in a large bowl to scoop out of. This is the basic mixture:

• 1 cup citric acid
• 1 cup baking soda
• 1/2 cup cornstarch

Mix the wet ingredients:  Mix 1/2 cup oil + drops of color + drops of essential oil in a separate bowl.

The type of oil, colors, and essential oils are all your choice. This is where there is a lot of room for experimentation and learning – the combinations are endless. For the oils, we used vegetable, olive, baby, and coconut. The colors we added using food coloring and liquid watercolor paint. For the essential oils, we used peppermint, tangerine, and Beautify ( from Aveda ). Repeat this process for every color and fragrance you want to make.

Add the wet mixture to 2 cups of the dry mixture and stir it together . If the mixture feels too dry and won’t stick together, add some more oil – a little at a time. If it’s too wet, add some more of your dry mixture. With a little experience, you’ll get a good feel for the right consistency. Your mixture should stick together pretty well by squeezing it in your fist but break apart when you pinch it.

Put the mixed-up bath bomb mixture in the molds.  Once you have the mixture, you want then add it to the molds you are using. Something as simple as a measuring cup as a mold works great. We also used sand toys from our kinetic sand for the kid shapes like starfish, alligators, and cupcakes.

We experimented by adding layers, putting bath pearls at the bottom of the cup (which will later be the top), putting Epson salts in the molds, and hiding toys inside the larger balls.  Here is an example of the bath pearls…

Pack everything together as hard as you possibly can. Once you have packed everything in really tightly, tap on the mold. It should pop out into the palm of your hand. Then lay out your bath bomb to dry either in a cupcake liner or on a paper towel. The oils will stain the paper as they dry.

Things you might want to know before you start.

Oil : You can use any oil that you want. We experimented with vegetable oil, olive oil, baby oil, and coconut oil. Try to keep it light. Some of the heavier cooking oils get, well, a bit oily in the tub when the bombs dissolve. I found that coconut oil was the nicest but let your kids play and see what they think. We learned – the fun way – to use oils instead of bubble bath to bind all of the ingredients together. We experimented to see if we could substitute the baby oil with bubble bath so our bombs would fizz AND bubble in the tub. This is what happened…

In a memorable way, our daughter learned that you couldn’t add the liquid soap into the mix, or it starts the fun fizzy part a little sooner than you want it to! Maybe something like a dry foaming bath powder would work, but we couldn’t find any.

Color : We used regular food coloring and talked about making new colors from the basic primary colors. We didn’t experience any staining in the bathtub but of course, be mindful of this before adding colors to your mixture. I had my daughter mix yellow+red to get orange, red+blue to get purple, and yellow+blue to get green. We also used some liquid watercolor paints that had glitter in them – that bathwater was shiny and beautiful. We experimented with making new colors by mixing the colors in the oil and by mixing the colors in the dry mix (and then adding oil separately).

The image on the left is red and blue food coloring mixed in the oil before adding it to the dry mix. The image on the right is red and blue food coloring mixed directly into the dry mix and then the oil added in separately. As you can see, it made a difference – the colors never truly combined when we mixed them right into the dry mixture.

Fragrance : Use any essential oils you want. We used peppermint, tangerine, and Beautify from Aveda but you could order a fragrance of your choice or use things you already have.

Again, experiment with things like – what happens if we add the vanilla extract from our spice cabinet for the smell? Depending on the age of the kids, you could really go nuts with experimenting with smells. Realize that if you use oils with a fragrance, they will compete with your essential oil fragrances. This is also a great time to introduce eyedroppers and how to use them – both great for a science connection and the fine motor skills of a child – they are tricky if you are learning how to use them as a kid!

Epson Salt: We used an Epson salt that had a nice lavender fragrance. So for that batch, we didn’t add any essential oils. We also noticed that it started to get dry partially through the mixture, and we needed to add more oil. We hypothesize that the salts were absorbing some of the moisture and drying it up – when we added a little more oil, it was fine.

While we were making these, I kept thinking, I wish my daughter were older because this would make a great science experiment to write up for a school project. What happens when you combine different oils, fragrances, and colors to make your own bath bombs? The charts the kids could make of their observations, the pictures, and the finished products would make this a great science experiment for school. Use the image below to PIN this idea for the next time you need a good science experiment.

I’d be lying if I said making your own bath bombs didn’t make a big mess and use tons of dishes – but hey, science can be messy! It all cleans up just fine in the end, and it’s worth the mess.

After the bombs are dry (overnight, probably), you can use them in the next bath your kids take or treat yourself to a nice relaxing bath. I’ll be saving some of the beautiful ones we made for gifts when my daughter has birthday parties to attend and at Christmas for grandparents and aunts. Luckily they are easy to make, so when we run out, we’ll make more! As a rough estimate, I would say that our homemade bath bombs came in at about 1/4 to 1/3 the price of store-bought ones. Still not super cheap, but at least we’re getting three baths now for the price of one!

I would love to see your students’ work if you decide to create any of my projects with them. Feel free to tag me (@artwithjennyk or #artwithjennyk) on social media so I can see what they make! You’ll find me on Twitter , Facebook , and Instagram ! 

Thank you for reading and for all you do!

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GREAT FOR ANY AGE

This lesson is very easy for teachers (low prep) but so much fun for kids! Each student is given one piece of a large mosaic collaboration poster to color according to the instructions on the page. Once all sheets are colored and cut out, they are then assembled to reveal a large multi-colored poster that says “We Heart Science.”

There are 30 poster pages, and the final poster is approximately 35 in. x 42 in. (depending on printer settings).

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The science of bath bombs

Have you ever wondered how bath bombs work? What is the science of that colourful fizzing ball in your tub? In the video below I did some experiments to find out. Have look at the video, and the explanation below, so next time you throw a Lush Experimenter bath bomb in your bath tub, you know what’s going on!

The bath bomb recipe

To make the bath bomb in the video, I followed a recipe with some adaptations. If you watched the video, you know that my version was functional, but had too much olive oil. So, below is a version of what I did, but with different oils!

Ingredients

• 200 gram baking soda
• 100 gram citric acid
• 100 gram cornstarch
• 100 gram epsom salt
• 1 tbsp water
• 1 tbsp almond oil
• 1 tbsp essential oils
• drops of perfume or food colouring

How to make the bath bomb:

• Mix all the dry ingredients together
• Mix all the wet ingredients together
• Very carefully, drop by drop, add the wet mix to the dry mix. Immediately after adding a drop the mixture will start to fizz a bit. Stir it right away and it will stop. Keep adding drops at a time and stirring or mixing with your hands until it gets the consistency of wet sand that just sticks together. Watch the video above to see what it looks like.
• Fill a bath bomb mold or a small bowl. Press it very tight and as full as possible. If you’re using a bowl or an open mold, press that onto a flat surface (like a cutting board) as hard as you can. If you have a mold that closes, pack both halves as full as possible and squeeze them together.
• Leave the bath bomb in the mold to dry overnight. Remove the mold and dry even longer. I left mine for a few days.
• You don’t have to use the exact same amounts as I did. The most important thing to get it to fizz is to have 2:1 weight ratio of baking soda to citric acid. The other ingredients are mostly to get it into a bath bomb shape, so you have a bit of freedom there.
• If you’re in the UK and can’t find food grade citric acid for sale anywhere, I used Scale Away ! As far as I can tell, citric acid is the only ingredient of this appliance descaler. If you use it to clean a tea kettle, you can probably also use it in the bath tub…

How do baths bombs work?

Now that you’ve made a bath bomb, it should work just like a store bought one. But why does it fizz? If you look at the ingredients above, most are not involved in the fizzing chemistry at all. Only three ingredients are important: baking soda, citric acid, and water.

When in water, the baking soda and acid start reacting together in an acid-base reaction . The citric acid is obviously the acid, and the baking soda is a base.

In the video, you can watch me do a very simple experiment to prove that these three ingredients are all required.

Experiment: What makes bath bombs fizz?

You will need:

• A bowl with baking soda (this is a base)
• A bowl with citric acid (this is an acid)
• An empty bowl

Take one teaspoon from the citric acid and transfer it to the third (empty) bowl. Take two teaspoons of baking soda and transfer that to the third bowl as well. Observe that nothing happened when you just added dry citric acid and dry baking soda together.

Now add a bit of water to all three of the bowls. The citric acid alone or the baking soda alone don’t fizz when you add water. But the bowl that has both will immediately start to bubble!

Note: If you live in an area with “hard water”, you will see a little bit of fizzing when you just add tap water to the citric acid. This is because the limescale in the water is a base, just like the baking soda.

What’s the chemical reaction?

So why the fizzing? When the citric acid and the baking soda react, they form new molecules. One of those molecules is carbon dioxide (CO2). This is a gas, and the sudden production of gas molecule in the mixture causes small bubbles to form. And that’s what you see when you throw a bath bomb in the tub!

(source: American Chemical Society .)

Eva Amsen is a writer, science communicator and blogger. She has been writing about science and scientists in art/culture/life since 2005, both on this blog and for other sites and publications. Portfolio | Twitter | Contact

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Great tip to try the bath bombs with my kids. Thank you for all the details

Oooh, this is soo cool! My daughter has been wanting to make bath bombs, so maybe this weekend, but I’d love to show her how they actually work. Love the video and how easy it will be for her to understand, since my explanation she just stared at me blankly haha. Thanks for sharing!

What fun. This would make a great birthday party activity and a little learning thrown in.

This is so cool! We are obsessed with bath bombs and they are not cheap – would love to go all science-y and make my own!

This is such a cool experiment! Absolutely loved it and will be passing it on to some young scientists I know.

I don’t use bath bombs bit was always intrigued by them. Thanks for breaking down how it works!now every time I see one I’m going to have the chemical reactions in mind lol!

Love bath bombs and I love how you broke it down. Real educational! Thanks

How fun! I have got to try this with my kids. They’d really enjoy it 🙂 thank you for sharing!

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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.)

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:

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.

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.

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 .

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

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

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