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Speedy Experiment – Lemon Volcano20/08/2020

I can’t say I’m a big fan of lemons. They’re just like oranges, but a more boring colour and with a horrible taste. But, like them or hate them, with a few simple ingredients, you can turn them into a lemon volcano! You don’t need time or a laboratory for this one; like the tremendous teabag rocket, the test takes less than ten minutes. Furthermore, it uses entirely household materials, so won’t harm the environment!

You will need:

  • A lemon – mine was quite an old one, which was good as it stopped me from wasting food.
  • A spoon
  • A knife (get a grown-up’s help for this one!)
  • Bicarbonate of Soda
  • A spare container; the second ramekin (little dish) in my photograph has a dash of washing-up liquid under the recommendation of another experimenter; however, I found that I didn’t need this.

The method:

1) Cut the two ends off of the lemon with the knife.

2) Use the spoon to core out some of the middle.

This should make a “bowl” shape like the image above.

3) Squeeze out the lemon juice from the lemon-ends into the spare container.

4) Add some bicarbonate of soda to your lemon-bowl.

The lemon juice will react with the soda and create an eruption. If your reaction is underwhelming, add a little of your spare lemon juice…

If you like, try testing the lemon volcano method with other citrus fruit. Does it work with lime? Orange? Grapefruit?

The science:

Bicarbonate of soda contains carbon – it’s in the name (bicarbonate) . When the citric acid in lemon juice reacts with the soda, those carbon dixoide atoms gain two oxygen atom companions each, and become carbon dioxide. Carbon dioxide is a gas, so that creates bubbles in the juice-and-soda – and because quite a lot of it is being produced, the lemon seems to erupt!

Speedy experiment – nervous coins22/07/2020

Your pocket money is alive! Well, sort of. Well, not really. But your coins will certainly seem alive after this experiment. You don’t need time or a laboratory for this one; like the tremendous teabag rocket, the test takes less than ten minutes. Furthermore, it uses entirely household materials, so won’t harm the environment!

You will need:

  • An old bottle – I used an old wine bottle; if your parents don’t have one of those about, you can use any any tall glass container
  • Coins – I tested two, but aim for multiple sizes (as long as one is large enough to cover the mouth of the bottle)
  • Some water
  • Access to a freezer

The method:

1) Remove the bottle cap, and place the empty bottle in the freezer.

2) While you’re waiting (at least five minutes), immerse your coins in water.

3) Remove the bottle from the freezer, and place one of the coins on top.

The coin should jump around and make strange clicking noises, like some sort of especially nervous robot. Try testing with other sizes of coin. Does it work if the coin doesn’t cover the entirety of the hole? What about with different coin materials? Do you have any coins from other countries that you could test?

The science:

As the helpful diagram below shows us, hot air rises.

Warm-Up: Why does hot air rise and cold air fall downward ...

On top of that, it also takes up a larger volume of space than cool air. This means that if you put cool air inside a container – for example, a recycled bottle – it will try to escape as it warms up.

When you take the uncapped bottle out of the freezer, the air inside the bottle begins to warm up, rising and expanding. The coin on top moves simply because the new larger air is pushing past it.

So, no, as far as we know, coins aren’t sentient. But they can jump about when air warms up behind them, and that is very fun to watch.