A colourful foam erupts from the top of a lemon

We all love to decorate our homes and make everything nice at Christmas. Some people like tinsel. Some people like a star on the top of the tree. That’s all fine – but what I never understand are the decorations that are made of a slice of orange with some smelly stuff shoved into it. There are much more exciting ways we can use oranges this Christmas – for science experiments!

There are quite a few things we can do with oranges and their neighbouring fruits lemons. For a start, both contain a fair bit of acid so we can do some reactions that make gas like carbon dioxide – you could even launch a rocket with the gas you produce!

There are also some colourful reactions you could do using that acid, like the erupting lemon volcano!

Just cut a lemon in half, add food colouring to the different segments of the lemon and then sprinkle some bicarbonate of soda over the top.

The other experiment that we can do with oranges and lemons doesn’t use the acid in them, though. We can use an oil in the skin of the oranges – limonene – to pop a balloon.

Just imagine sitting at the Christmas table this year and challenging people to pop a balloon without even touching it. No pointy things or sharp objects allowed – just pop the balloon. You’ll know the trick and can wow everyone…

Here’s how:

Blow up the balloon – you want it to be stretched really taut to make it easier. The more you blow the balloon up the more stretched the rubber gets and that makes it thinner and thinner… this is why it will pop eventually because it will get stretched so thin that it isn’t strong enough to hold the air back any more.

Now peel the skin of an orange – you’ll need one of the really thick skinned oranges to have the best chance of this working. It depends on how long the oranges have been stored before you get to buy them and whether they have been coated in wax to help the shops keep them fresh for longer.

Take a big piece of peel and hold it close to the balloon. Point the orange side of the peel towards the balloon and then bend it and twist it and squeeze it. You’ll spray a fine mist of oil out over the balloon and cover the rubber in limonene. Here’s a slow-mo shot with backlight to show that it’s the oil from the peel that hits the balloon and causes the pop!

The limonene can get into the material of the balloon and start to move around inside the rubber, making it more flexible and soft. Eventually the rubber becomes so flexible that the air inside pushes it too hard and pop! The balloon will explode.

Lemons and oranges will both work for this but it’s harder to peel a lemon. The reason both of them work is that they both have this molecule limonene in their skin. The limonene causes the smell of both the lemon and the orange but one is ‘left-handed’ and one is ‘right-handed’ and your clever nose can actually tell them apart!

Try out some of these citrus experiments this Christmas!

Tags:

No responses yet

Leave a Reply

%d bloggers like this: