← Little Scientists ScienceBubbles of gas15 minutesStd 1–2

Dancing Raisins

✨ The raisins rise to the top, wobble and sink again, over and over, as if they had learned to dance.

A glass of fizzy water where a raisin at the bottom collects gas bubbles and rises, then the bubbles pop at the surface and the raisin sinks again, drawn as a loop. — How it works

🧰 You need

a tall clear glass
water
one teaspoon of baking soda
a few spoons of vinegar
six raisins or sultanas
a spoon

👀 What you will see

The liquid fizzes and tiny bubbles cling to the wrinkled skin of every raisin. A raisin carrying enough bubbles lifts to the surface, where the bubbles burst with a small pop. With its bubbles gone it sinks again and starts collecting new ones.

🧪 Do it

Fill the tall glass three quarters full of water and stir in one teaspoon of baking soda.
Drop in the raisins and watch them settle at the bottom.
Pour in a few spoons of vinegar and stand back a little.
Watch the raisins for two minutes without touching the glass.
Count how many times one raisin travels up and comes down again.

💡 Why it happens

Vinegar and baking soda react together and make a gas called carbon dioxide, and the bubbles you see are that gas. A bubble is far lighter than the same amount of water, so a raisin wearing bubbles becomes light for its size and floats up. At the surface the bubbles escape into the air, the raisin becomes heavy for its size again and down it goes. The dance keeps going for as long as the fizzing keeps making new gas.

🔁 Now try this

Try the same fizzy glass with a grape, a lentil and a small piece of dry pasta, and find which one dances best.

🤔 Think about it

Why does a smooth glass marble never dance, even in the fizziest glass?

🧘 Ask the Acharya

“Why does a smooth glass marble never dance, even in the fizziest glass?” — ask him and he will explain it from your own chapters.

Ask Guru →

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