Extreme Drawing

Baking soda and vinegar experiment: the fizzing volcano

Kitchen science experiment

Make a fizz that runs like lava

Vinegar is an acid and baking soda is a base. When they meet, they react and make carbon dioxide gas, so the mixture foams up, overflows like lava and then goes flat once one of them is used up.

Play in your browserDo it for real
  • Ages 4+
  • 15 minutes
  • With an adult
Painted illustration of the painter pouring red vinegar onto a heap of baking soda on a tray, which fizzes up into pink foam.

Quick facts

Age
4 to 10 (little ones with help)
Time
About 15 minutes
Mess
Medium: do it on a tray
Adult needed
Yes, to pour and to keep vinegar out of eyes
You need
Baking soda, vinegar, food colouring (a few pence/cents)
On screen / for real
Both

In Extreme Drawing

Open the Science tab. Shake the Baking soda sieve to dust a white heap onto the paper, then pick Vinegar and let drops fall on it. The heap fizzes up into a foam that rises, runs downhill like lava and then collapses, with a hiss. The white powder is really used up as it fizzes, so a big heap keeps going longer than a thin dusting.

The foam takes the colour of whatever dye is in the paper under it. Choose Red vinegar, Blue vinegar or Yellow vinegar, or drip Food colouring first and dust the soda over it, and every patch fizzes in its own colour. The acid soaks along through wet paper and through the fizz itself, so one drop can set off a whole heap.

Things to try:

  • Any acid fizzes, not just vinegar: put a lemon slice (Kitchen) or lemon-juice secret ink on the soda. Vinegar fizzes harder than juice.

  • Paint red cabbage juice first: it turns pink where the vinegar lands and green where the soda lies.

  • Dust soda in a pattern with the sieve, then drip vinegar along it and watch the fizz travel down the line.

Play in your browser
Painted illustration of the painter, goggles on his beret, studying a bottle foaming over in stripes, with red cabbage juice in pink and green glasses and fizzing baking soda.

Do it for real: a coloured volcano

You need

  • A tray, baking dish or the kitchen sink

  • A small cup, jar or plastic bottle (open at the top)

  • Play dough, modelling clay or damp sand for the volcano (optional)

  • 2 to 3 tablespoons of baking soda (UK: bicarbonate of soda)

  • About 100 ml (half a cup) of white vinegar

  • Food colouring

  • A squirt of washing-up liquid (dish soap) for extra foam

  • Goggles or sunglasses if you have them

Why you never mix bleach and vinegar

  1. Set up somewhere wipeable

    Put the tray on a table you can wipe, or work outside. Put on goggles if you have them.

  2. Build the volcano

    Stand the cup in the middle of the tray. Press play dough or clay round it into a mountain, leaving the top of the cup open. (A plain cup works too.)

  3. Load the soda

    Spoon 2 tablespoons of baking soda into the cup. Add a few drops of food colouring and a small squirt of washing-up liquid.

  4. Predict

    Ask: how high will it go? Will it fizz for a long time or a short time? What colour will the lava be?

  5. Pour the vinegar

    The grown-up pours the vinegar in, all at once for a big eruption or a little at a time for a slow one. Step back and watch.

  6. Find out what ran out

    When it stops, add a splash more vinegar. If it fizzes again, there was soda left over. If not, add a spoon of soda instead: now the vinegar was left over.

  7. Try the Extreme Drawing way

    Sprinkle a thin layer of soda over the tray and drip coloured vinegar on it with a spoon or pipette. Every drop fizzes in its own colour.

Painted illustration of the painter pouring purple red cabbage juice into a row of glasses that go from pink through purple and blue to green, with a lemon and baking soda.

Why it works

For kids: vinegar is an acid and baking soda is a base. When they touch, they swap parts and make something new: a gas called carbon dioxide, the same gas that makes the bubbles in fizzy drinks. The gas makes bubbles, and the bubbles make the foam.

For grown-ups: sodium bicarbonate (NaHCO₃) reacts with the acetic acid in vinegar (CH₃COOH). The carbonic acid that forms breaks down straight away into water and carbon dioxide (CO₂), leaving sodium acetate dissolved in the water: NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂. The washing-up liquid traps the gas in longer-lasting bubbles. The fizz stops when one reactant runs out (the limiting reactant), which is what step 6 tests. A new substance forms, so this is an irreversible change. The reaction also takes in a little heat: a cup of it feels slightly cooler.

In the game every spot of paper has its own acidity, and anything acidic fizzes with soda by the same rule. Nothing in the code pairs "vinegar" with "soda" by name, which is why lemon works too.

Try next: predict, then test

Vinegar or lemon juice?

Which fizzes harder? Test both on the same amount of soda, then check on screen.

More soda or more vinegar?

Which one makes the eruption bigger, and which one makes it last longer?

Warm or cold vinegar?

Does warm vinegar (from the tap, not boiling) fizz faster than vinegar from the fridge?

Does it get colder?

Hold the cup while it fizzes. Does it feel warmer or cooler than before?

For teachers

This experiment fits KS2 Year 5 "properties and changes of materials", where the action of acid on bicarbonate of soda is a named example of an irreversible change, and NGSS 5-PS1-4 (mixing two substances can make a new one). Show the fizz on the whiteboard first, ask the class to predict, then do the volcano on a tray.

Reversible and irreversible changes lesson

Questions about baking soda and vinegar

Is baking soda the same as bicarbonate of soda?

Yes. Baking soda (US) and bicarbonate of soda or bicarb (UK, Ireland, Australia) are both sodium bicarbonate. Baking powder is different: it already contains an acid, so it fizzes with plain water and gives a weaker volcano with vinegar.

What gas do baking soda and vinegar make?

Carbon dioxide. It is heavier than air, so it pools low around the volcano before it drifts away.

Why does the fizzing stop?

One of the two has been used up. Add more vinegar: if it fizzes again, there was soda left; if not, the soda ran out first.

Is the baking soda and vinegar experiment safe for kids?

Yes, with an adult: both are kitchen ingredients. Keep vinegar out of eyes, never seal the mixture in a closed bottle, and never mix vinegar with bleach.

Can I make a volcano without vinegar?

Yes, with any kitchen acid such as lemon juice. It fizzes a bit more gently than vinegar.

More fizz and colour

Painted illustration of the painter in oven gloves sniffing a golden loaf, with a ball of dough, a rolling pin, a bowl of yeast and a pretzel.

Bread and yeast

Soda bread rises with this same fizz, trapped inside the dough.

Fizz it on screen first

Dust the soda, pick a coloured vinegar and watch the lava run. Then build the real one on a tray.

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