Science Experiments

Coke Can Eruption

Sun, 24th Jun 2007

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What you Need

At least 2 cans of fizzy drink

A hand

What to do

Shake up both cans

Leave them on their side for 10-15sec

Turn them upright.

Tap one sharply on the top 4-5 times

Wait 10sec

Open both cans.

Is there any difference.

What may happen

The theory is that the can that  you tapped should froth out less than the one that you didn't.

Why does it happen?

An Unshaken Can

Opened Can

Fizzy drinks are fizzy because they have loads of carbon-dioxide dissolved in them under pressure.

So when you release the pressure by opening the can the carbon-dioxide will come out of the liquid. Bubbles are difficult to start so if the can is clean not many bubbles will form.

Shaken Can

Frothing Coke Can

If you have shaken the drink you will have mixed a whole lot of bubbles into the liquid.

These  bubbles have already started so if you open the drink immediately the bubbles can expand rapidly creating foam. This foam is much larger than the can so the drink will splurt out.

Stuck Bubbles

Tapping the Can

Often when you shake a can bubbles get stuck to the sides which will stay there until they dissolve which will take 10s of minutes.

If you tap the can it will dislodge some of the bubbles and if you give them long enough to reach the surface it should reduce the amount of foam produced.

Dave Ansell


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