One of my favorite science experiments to do with kids is the volcano reaction. It's a classic that never gets old. My kids and I have experimented with many variations of the volcano - it's actually the origin of our shared love for exploring science together.
One of the more memorable times we had with this experiment happened outside. The kids were creating a volcano using a pile of dirt with a crater in the backyard. They were so excited to watch their mountain erupt! Using a measuring spoon, they took turns adding baking soda to the crater. Next came the vinegar. As we watched the eruption, something unexpected happened.
The vinegar hit the baking soda and started fizzing in the crater. We waited for the lava to come out the top, but we soon noticed the volcano was erupting... sideways! Our creation had a mind of its own, and the foamy "lava" decided to escape through a crack in the side.
Although our volcano experiment didn't go completely as expected, we embraced the chaos and enjoyed the sideways volcano. After the mishap, we patched up the crack for a smoother reaction next time. We learned that science experiments don't always go as planned, but that's part of the fun and discovery!
Since then, we've enjoyed adding twists to the classic volcano experiment. We've found ways to make a more foamy reaction, we've added colors, and even made the "lava" glow! Follow the step-by-step guide below for more inspiration on how to create the best volcano reactions.
Science behind the volcano reaction
The volcano reaction involves the interaction of an acid and a base, resulting in the production of carbon dioxide gas, water, and a salt compound. In the guide below, the acid is either vinegar (acetic acid) or citric acid, while the base is baking soda (sodium bicarbonate).
Acid-Base Reaction: An acid is a substance that donates hydrogen ions (H+) when dissolved in water, while a base is a substance that accepts hydrogen ions or donates hydroxide ions (OH-). When an acid and a base come into contact, they undergo a chemical reaction known as an acid-base reaction or neutralization reaction.
Reaction with Vinegar (Acetic Acid): When vinegar (CH3COOH) comes into contact with baking soda (NaHCO3), the following acid-base reaction occurs:
CH3COOH (acetic acid) + NaHCO3 (sodium bicarbonate) → NaCH3COO (sodium acetate) + H2O (water) + CO2 (carbon dioxide)
In this reaction, the acetic acid (acid) donates a hydrogen ion (H+) to the baking soda (base), resulting in the formation of sodium acetate (salt), water, and carbon dioxide gas. The carbon dioxide gas released during the reaction creates the foamy eruption, while the water and salt remain dissolved in the mixture.
The reaction with citric acid is similar, although instead of forming sodium acetate as the salt, sodium citrate is formed.
Adding soap to the eruption
Soap is a complex compound, typically composed of long hydrocarbon chains (made up of carbon and hydrogen atoms) with a polar "head" region (which is hydrophilic, or water-loving) and a non-polar "tail" region (which is hydrophobic, or water-repelling). This unique structure allows soap molecules to lower the surface tension of water, creating bubbles and foam.
When soap is added to the baking soda and vinegar or citric acid reaction, its molecules surround and encapsulate the carbon dioxide gas released during the reaction. The hydrophobic tails of the soap molecules cluster together around the carbon dioxide bubbles, while the hydrophilic heads remain attracted to the surrounding water. This stabilizes the bubbles and creates the foam eruption that enhances the visual excitement of the volcano experiment.
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You will need:
A volcano (Make your own with this kit, use an Erlenmeyer flask, mold one with Play-Doh, or go outside and make one with dirt or sand mixed with water)
2 Tablespoons baking soda
1 Tablespoon citric acid (or 1/4 cup vinegar, see note)*
1/4 cup water (leave out if using vinegar)
1 teaspoon dish soap as surfactant (optional but recommended for more foamy reaction)
Optional Additions:
Several drops of food coloring
1 teaspoon glow powder
1 teaspoon glitter
Step 1: Get your volcano ready
Start by placing your volcano of choice on a plate. Or if you are opting outside, start building your volcano in dirt or sand, adding in a little water to strengthen the structure.
Step 2: Add the baking soda
Using a measuring spoon, scoop two Tablespoons of baking soda to the "crater hole" on top of your volcano.
Step 3: Add the citric acid
If you are using citric acid powder for this experiment, add one Tablespoon to the baking soda in the crater hole. Mix together with a spoon. I prefer to use citric acid because I feel more comfortable letting kids mix soap into water and pouring that mixture rather than vinegar, just to avoid any skin sensitivities if the vinegar spills or splashes. If you use vinegar, just skip this step and move on to the next one.
Optional Step: Add the extras
To add extra excitement to this reaction, mix in the optional add-ins. You may choose to add in a generous scoop of glitter for extra sparkle, or glow powder. If you use glow powder, it will work better if you first activate the glow powder by shining direct light for several minutes. Then go into a dark room for the reaction. If you are using food coloring, add this to liquid in the next step.
Step 3: Mix soap into the liquid
If you are using citric acid, mix 1 Tablespoon of dish soap into 1/4 of water. If you are using vinegar, add soap directly to the vinegar and leave out the water. This is also a great time to add in food coloring if you are using it.
Step 5: Start the reaction
Slowly pour your liquid into the crater hole and watch your eruption take place! Remember to turn out the lights if you are using glow powder.
The volcano reaction is a very fun demonstration of an acid-base reaction. The interaction between the acid (vinegar or citric acid) and the base (baking soda) produces a salt compound, water, and carbon dioxide gas. The addition of soap enhances the foam formation, adding an extra element to the eruption. Plus there are so many additive options such as glow powder or dyes to elevate your reaction even more. Through this experiment, witness the exciting chemical reactions that occur when acids and bases meet, providing a glimpse into the field of chemistry. Have fun!
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