Scientific experience: A volcano in the house !!!

Following the experiment we did on crystals (see here), our son was very eager to discover new scientific experiences. So I rummaged a little the web, and we opted for an experiment consisting of making a small volcano at home.

This experience involves vinegar / baking soda and is a classic. Many variations exist, and can be achieved on the same basis: a taking-off rocket, a balloon that swells without blowing into it, and so on.

I choose the volcano version because it is simple and fast to achieve. In the same afternoon, we made two different versions (because children always ask for more). The classic version and this one, allowing the phenomenon to be observed for a longer time thanks to the appearance of foam.

Starting Question

How does a volcanic eruption occur?

Phenomenon to be observed

Chemical reaction between two products, acid-base concept

Materials needed for the experiment:

• A glass, a cup or a small bottle
• Warm water
• Dishwashing soap
• A glass of white vinegar (about 200 ml)
• Sodium bicarbonate (2 tbsp)
• Food coloring (some are using red ink or grenadine syrup)
• A large bowl

Optional: sand or soil to make a ‘mini-volcano’.

@moelflow used clay or wax to make his volcano: the advantage is that it can easily be reused, but still it must be at home! See here for more information.

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Step 1: Making the volcano

Put the glass (or the plastic bottle) in a large bowl, and prepare the "volcano" with sand or soil leaving only the top of the glass or the neck of the bottle uncovered.

Step 2: Mix

Pour lukewarm water into the glass (say about 1/4) and add a few drops of dishwashing liquid, a few drops of red food coloring (for volcano lava effect) and sodium bicarbonate.

Now pour the vinegar quickly into the glass.

Step 3: Observe

The foam forms, emerges through the neck and flows over the sand like lava on the sides of the volcano.

Be careful, however, when pouring the vinegar: if the neck of the bottle is narrow, the explosion can be quite impressive ... it is better to avoid having the face right above it!

The foam thus formed lasts long enough and the children can then play with it safely.

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Questions asked to Zachary, 6 years old

How does a volcanic eruption occur?

Lava is melted rock and sinking fire, when the (tectonic) plates move, the lava explodes.

What do you think happened here? There is no magma or heat?

We put some bicarbonate and vinegar, it brought out the food coloring, and render it like a volcano.

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Scientific explanations of the phenomenon

Sodium bicarbonate is a compound with a basic pH while vinegar has an acidic pH. When these two products are put in contact, a chemical reaction occurs: an acid-base reaction.

It is not easy to explain this reaction in detail without entering into the chemical formulas, which I will avoid here. After all, the purpose of the experiment is to interest children in science, not to make them confused from the start!

Let's just say that this reaction produces something completely different from the two original products, something new that is neither vinegar nor bicarbonate: carbon dioxide, which is a gas, and water.

It is the carbon dioxide that yields the bubbles, and that makes the foam possible to be formed! The dishwashing liquid makes it possible to observe this foam longer.

In the case of a volcano, water and vinegar represent magma. The magma is composed of very hot rocks that have melted, much like an ice cube that melts when heated, but at temperatures much higher than that of the stove!

There are also gases that accumulate underground and create pressure. When the pressure increases too much, it causes the magma to spring out of the volcano: it is the volcanic eruption.

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Commentary by Zachary after explanation of the phenomenon

It's like dad when he's farting: he says he has gas ...

Indeed, it is a fairly similar phenomenon, but still different and a little more complex. It is called fermentation. We will wait a few years for testing the change of grape juice into wine… ;)

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References :

• @moelflow Steemit article
• Ref. 1
• Ref. 2
• Ref. 3
• Ref. 4

For other experiments with sodium bicarbonate, see here