Year 3 Science Experiment

Build a Volcano

Create your own volcanic eruption using a chemical reaction between baking soda and vinegar!

Adult supervision recommended for younger children.

This experiment can be messy! Do it outside or on a large tray. Food colouring may stain surfaces.

Safety First!

• Do not taste or drink the vinegar-baking soda mixture.
• Wear old clothes — food colouring can stain.
• Keep the eruption away from electronics and anything that should not get wet.
• Do this experiment outdoors or on a large tray to catch the overflow.

You Will Need

✓ A small plastic bottle (empty, ~250-500ml)

✓ Baking soda (2-3 tablespoons)

✓ White vinegar (about 1 cup)

✓ Dishwashing liquid (a squirt)

✓ Red and yellow food colouring

✓ Sand, clay, or playdough (to build the volcano shape)

✓ A large tray or baking dish

✓ Warm water

Step-by-Step Instructions

Build Your Volcano

Place the empty plastic bottle in the centre of your tray. Build a volcano shape around it using sand, clay, or playdough. Leave the opening of the bottle exposed at the top — this is the crater! Make it look like a mountain with slopes on all sides.

Add the Baking Soda

Carefully add 2-3 tablespoons of baking soda into the bottle through the opening. You can use a funnel or rolled-up piece of paper to help.

Add the Extras

Add a good squirt of dish soap into the bottle (this makes the eruption foamier). Add a few drops of red and yellow food colouring to make it look like real lava. Add a splash of warm water and give it a gentle swirl.

Prepare for Eruption!

Make sure everyone is watching. Have your vinegar ready to pour.

ERUPT!

Pour the vinegar quickly into the bottle and step back! Watch as the "lava" foams and flows over the top of your volcano, running down the sides just like a real eruption!

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Do It Again!

You can repeat the eruption by adding more baking soda and vinegar. Try changing the amounts — what happens with more vinegar? More baking soda?

What Happened?

When you poured vinegar onto the baking soda, a fizzy, foamy "lava" erupted from the bottle and flowed down the sides of your volcano. You may have heard a fizzing sound and seen lots of bubbles.

This happened because vinegar (an acid) reacted with baking soda (a base). When they mix, they create a chemical reaction that produces carbon dioxide gas (CO₂). The gas forms bubbles, and the dish soap traps these bubbles into foam, making the eruption look bigger and more dramatic.

The gas builds up pressure inside the bottle and forces the foamy mixture out through the opening — just like lava erupting from a real volcano!

The Science Behind It

This experiment demonstrates a chemical reaction — when two substances combine to form new substances that did not exist before.

Vinegar contains acetic acid (an acid). Baking soda is sodium bicarbonate (a base). When an acid and a base meet, they react.

The reaction produces three new things: water, sodium acetate (a type of salt), and carbon dioxide gas (CO₂). The CO₂ gas is what makes all the bubbles and fizzing.

Real volcanoes work differently — they erupt because of extreme heat and pressure deep underground that melts rock into magma. When the pressure gets too high, the magma forces its way to the surface. But the shape and flow of your model helps you visualise what a real eruption looks like!

Australian Curriculum link: Science Year 3 — A change of state between solid and liquid can be caused by adding or removing heat. Earth's surface changes over time as a result of natural processes (AC9S3U02, AC9S3U03). Chemical sciences: substances can change when mixed.

Think About It

How is your model volcano different from a real volcano? What is the same?

What would happen if you used lemon juice instead of vinegar? (Hint: lemon juice is also an acid!)

Can you think of other places where you see chemical reactions producing gas? (Think about baking a cake...)

People who live near real volcanoes face real dangers. What should communities do to prepare for volcanic eruptions?

Key Concepts Summary

● A chemical reaction happens when substances combine to form new substances.
● Acids (like vinegar) and bases (like baking soda) react together.
● This reaction produces carbon dioxide gas (CO₂), which causes fizzing and bubbling.
● Real volcanoes erupt due to heat and pressure deep inside the Earth, not chemical reactions like our model.
● Models are useful in science because they help us understand and visualise things we cannot easily observe.

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