How to simulate a volcanic eruption with an acid and a base

Safely creating an erupting ‘volcano’

When a liquid acid is mixed with a solid carbonate base such as powdered bicarbonate of soda, carbon dioxide gas is produced.

The resulting mix is a gas plus a liquid instead of a liquid plus a solid, which takes up more space.

If a flask is used to simulate the magma chamber of a cone type volcano, the gas-liquid mix will rise up dramatically to create a simulated eruption. Adding red food dye to the mix completes the illusion.


Step 1

Get the ingredients together

Fill the flask a quarter full of water. Add red food coloring and swirl to mix. Next add acid to raise the level to half full. Set the flask in a flat container such as a baking dish to catch the overflow.

Step 2

Add the acid

Any acid will work. In the school laboratory, weak hydrochloric acid is a good choice. In the kitchen, cheap vinegar is an excellent choice because it is safe and easy to use.

Step 3

Add the bicarbonate of soda and stand back

The addition of a bicarbonate base starts the reaction. The base reacts with the acid to form a salt, water and carbon dioxide gas.

acid + carbonate base —> water + salt + carbon dioxide

Step 4


The carbon dioxide and liquid mix move up the flask like molten magma up the magma tube to the top of the volcano.

The result is a beautiful eruption.

Step 5

Clean up the mess

You will be grateful that you used a dish when you clean up the mess.

Food coloring is mildly staining but bleach will remove it.

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Things Needed
• Acid such as vinegar
• bicarbonate of soda
• flat bottomed flask
• red food coloring
• container to catch the overflow

Tips & Warnings
• Be sure to put the flask in a baking dish or other container to collect the overflow as this experiment is quite messy
• This could be a Science Fair experiment.


Comment: 2
    Judson  24.10.2017 06:24

    The eruption usually lasts for about a minute and there are several bursts of bubbles. I just lucked out with that photo!

    Ridings  24.12.2017 00:23

    Keeping this experiment up my sleeve for next time grandson visits; he’ll love it!! Gosh even I might try it beforehand so I know what I’m doing! Great picture you got; wonder did you have a special speed, or just set on auto to capture that special moment. How long does the eruption last; is it just that single burst?

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