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Vacuuming marshmallows

By David Shaw, 27 June 2019

This vacuum chamber really sucks!

In this hands-on activity, you’ll make your own vacuum chamber and watch marshmallows turn into fluffy clouds of sugar!

You will need

• Cheap wine-preserving pump*
• Small glass bottle. The mouth needs to be big enough to fit a marshmallow and small enough to fit the pump.
• Marshmallows

*If you can’t find one to borrow, you can buy these from some liquor stores and homeware stores.

What to do

1. Clean and dry the bottle. If it has any labels on it, take them off so you can see inside easily.
2. Put a marshmallow in the bottle.
3. The pump should come with plugs. Put one plug on the end of the pump and make sure it will seal nicely over the mouth of the bottle.
4. Put the plug on the bottle and start pumping. Watch what happens to the marshmallow.
5. When you’ve pumped as much as you can, take the pump off. Then watch the marshmallow as you take the plug off the bottle.
6. Try pumping and releasing the same marshmallow a few times. Does that affect what happens?
7. You can also try putting shaving foam or whipped cream in your vacuum chamber!

What’s happening?

Air might seem like empty space, but it’s actually packed with molecules. In one teaspoon of air, there’s about 100 million million million moving molecules! These molecules bang and crash into surfaces, and the pressure of these pushing molecules is known as air pressure.

Marshmallows are filled with tiny bubbles, and the air molecules in the bubbles are pushing against the marshmallow. Usually, that’s balanced by the pressure of air outside the marshmallow.

When you place the marshmallow in a bottle and start pumping, you reduce the number of air molecules – and therefore the air pressure – surrounding the marshmallow. As air in the bottle is removed, the air molecules inside the marshmallows can push harder in comparison, so the marshmallow pushes out and takes up more space.

As you take the plug off, air molecules rush into the bottle. The molecules push hard on the marshmallow and shrink it back down again. The marshmallow will probably end up a bit smaller than at the start – some of the bubbles in the marshmallow will pop, making it a bit less aerated.

More information

Check out this video about suction

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