The baking soda volcano experiment is a classic, and most of the time it gets done as a show: pour, fizz, wipe the table, done. Done right, the baking soda volcano experiment is a real chemistry lesson and a real fair test, using only kitchen supplies. Below: the recipe, the science in words your child can repeat, and three ways to turn it into a baking soda and vinegar volcano science project.
How to do the baking soda and vinegar volcano experiment
This recipe follows the USGS and National Park Service volcano lesson, scaled for a kitchen tray6. The tissue trick is the clever part: it lets your child drop all the baking soda in at once instead of spooning it in slowly.
The classic volcano
- A small plastic bottle (8 or 9 oz)
- Household white vinegar
- Baking soda and a teaspoon
- One sheet of tissue
- Optional: food coloring, dish soap
- A baking tray
- Goggles for everyone close by
- Adult supervision the whole time. Goggles on.
- Pour vinegar in until the bottle is at least one third full6. Add the food coloring and soap now if you use them.
- Put one heaping teaspoon of baking soda on the tissue and roll it into a little bundle6.
- Ask for a prediction: "What will happen? How high will it go?"
- Drop the bundle in and step back. Do not cover the opening.
- Touch the bottle. Warmer or colder? (Colder: kids are always surprised4.)
Why it fizzes: an acid plus a base makes carbon dioxide gas
Here is the chemistry in one line. Baking soda is sodium bicarbonate. Vinegar contains acetic acid. When they meet, they make sodium acetate, water and carbon dioxide, and only the carbon dioxide is a gas5. Those gas bubbles push the liquid up and out of the bottle. That is your lava.
Ohio State's Wonders of Our World program calls baking soda and vinegar a well-known acid-base reaction8. The same move shows up in a classic book experiment with chalk:
Vinegar is an acid. It makes the bones bend and the chalk fall apart.1
The chalk bubbles because chalk, like eggshell, contains calcium carbonate, and an acid reacting with it also makes carbon dioxide gas1. Different starting stuff, same gas.
A kind of substance that tastes sour in foods, like vinegar or lemon juice18. In experiments we look, we don't taste.
Say it: “Which of our kitchen things do you think is an acid?”The opposite team to an acid. Baking soda is a base8.
Say it: “What happens when the two teams meet?”Is a volcano science experiment like a real eruption?
Partly, and the honest answer makes a better volcano eruption science project. Gas really does power eruptions. USGS scientists explain that gases dissolved in magma expand when pressure on the magma is released, like a shaken soda bottle opened fast7. The main gases are water vapor, carbon dioxide and sulfur gases7.
The difference: in a real volcano, the gas is not made by a sudden chemical reaction, and in most eruptions water, not carbon dioxide, is the main gas doing the pushing6. Say it plainly to your child, and the model becomes a talking point instead of a myth.
The best volcano project is the one that says what the model gets wrong.
Make it a baking soda volcano science fair project: 3 fair tests
One eruption is a demo. A science fair project needs a question and a fair test: change one thing, measure one thing, keep everything else the same. Those same-every-time things are the constants:
Constants are the factors within an experiment that are kept the same for all2
The one thing you change is the independent variable. The thing you measure is the dependent variable, the one that responds2. And you run each version more than once, because repeated trials reduce the effect of measuring mistakes and small differences2.
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01Use a tall clear cup.
Mark a strip of masking tape every half inch up the side to read the foam height.
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02Measure the vinegar every time.
The chemistry teachers' version uses the same 50 mL of vinegar in every run4.
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03Change one thing only.
Pick Test 1, 2 or 3 below. Everything else stays the same2.
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04Three tries each.
Fresh cup each run. Repeating is part of a strong design2. Use the middle number.
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05Write it down.
Question, prediction, method, results, conclusion: the experiment words in DK's 1000 Words STEM3.
Test 1: does more baking soda make a bigger eruption?
Keep the vinegar at 50 mL and change only the baking soda: half a teaspoon, 1, 1 and a half, then 2 teaspoons. That is exactly the design a second-grade teacher uses in the American Association of Chemistry Teachers lesson4. Measure the highest foam line each time.
Test 2: vinegar or lemon juice? (a lemon volcano experiment)
Lemons contain citric acid, which gives them their sour taste, and citric acid reacts with baking soda much like vinegar does, releasing carbon dioxide8. Keep the baking soda the same and swap 50 mL of vinegar for 50 mL of lemon juice. An adult does any cutting8. Which acid makes more foam?
Test 3: soap or no soap?
Ohio State's lemon volcano adds dish soap to trap the gas in bubbles and make a foam8. Run the recipe with and without one squirt of soap. Does soap make more gas, or just catch the gas you already had?
| Version | Try 1 | Try 2 | Try 3 | Middle number |
|---|---|---|---|---|
| EXAMPLE: 1 tsp baking soda | 3 marks | 4 marks | 3 marks | 3 marks |
| ____ | ____ | ____ | ____ | ____ |
| ____ | ____ | ____ | ____ | ____ |
| ____ | ____ | ____ | ____ | ____ |
The bubbles are just air.
They are carbon dioxide, a new gas made by the reaction5.
Bonus: egg experiments with vinegar
Want a slow-motion version of the same chemistry? STEPS to STEM puts a raw egg in a glass of vinegar. The shell is calcium carbonate, and the acid dissolves it; it can take 12 to 24 hours to dissolve a good part of the shell, and you may need fresh vinegar to finish1. Watch for tiny bubbles on the shell: the same carbon dioxide1.
Then rinse the shell-less egg and set it in plain water overnight. It swells, because water passes through the membrane once the shell is gone1. Nobody eats it.
- A question in one sentence
- Your prediction, written before testing
- What you changed and kept the same
- Your results chart, all three tries
- A conclusion, plus one way the model differs from a real volcano
What to expect by age
Frequently asked questions
Is the baking soda volcano science experiment safe for kids?
Yes, with simple rules: goggles on, nothing tasted, and the bottle never capped while it fizzes45. Use household vinegar, never anything stronger than 7% acetic acid5. Do it outdoors or on a tray6.
How does a volcano eruption science experiment work?
Vinegar (an acid) and baking soda (a base) react and make carbon dioxide gas, plus water and sodium acetate5. The bubbles push the liquid up and out, like lava.
How do you make a baking soda and vinegar science project a fair test?
Change one thing, like the amount of baking soda, and keep everything else the same, like 50 mL of vinegar each time24. Measure one result, such as foam height, and run each version three times2.
What can you use instead of vinegar in a volcano experiment?
Lemon juice works: it contains citric acid, which reacts with baking soda and releases carbon dioxide8.
Why does the volcano science fair project get cold?
The temperature drops during the baking soda and vinegar reaction, and the AACT lesson notes that second graders are always shocked by it4.
Keep exploring
- Ramps, cars and your child's first fair test The same change-one-thing idea, with toy cars.
- Air is not nothing More experiments where an invisible gas does the pushing.
- "How do you know?" How to talk about results like a scientist.
If you want a project in the mail
Everything above runs on kitchen supplies. If you would like a new hands-on project arriving each month to predict, test and talk about, there is our Club.
ClubA sealed box for every monthMonthly at $39, or $29 a box on the 12-month plan. Siblings pay less.from $29GoP Toys sells the Club mentioned above. None of the sources cited tested our products.