What is money made of? Chemistry!

by Rosie Coates

What is in your wallet?  Some coins perhaps and maybe some paper money if you’re lucky! You also have a whole load of chemistry.

Your ‘coppers’ aren’t copper, nor is your ‘silver’ money silver.

1p and 2p pieces used to be bronze but are now copper-plated steel and the other coins are alloys (a mixture of two or more different metals).

5p, 10p and 50p pieces are made up of 75% copper and 25% nickel and a pound coin is 70% copper, 5.5% nickel and 24.5% zinc.

Why not use real copper, silver and gold?  

If we did the value of the metal that makes the coins would then be worth more than the face value of the coin.  Before 1992 1p coins were 97% copper; in 2006 the price of copper was so high that the scrap metal value of one of the copper coins was 1.5p!

Pure metal coins wouldn’t actually stand up to being used for very long.

'Silver' coins from the rein of Elizabeth II

‘Silver’ coins. Image: Public Domain

 

Alloys are mixtures (rather than chemical compounds). One of their great advantages, over pure metals, is that they tend to be harder than the metals they are made from.

The atoms of different elements are different sizes, making it harder for them to move over each other than in the pure metal, resulting in a harder material.  Great news if you’re making coins as you can produce money that can withstand being bumped around in our wallets, parking meters and occasionally the washing machine without being damaged too much.

Giving your coins a chew to check if they’re real

You might have seen pirates in films and cartoons biting on a gold coin to check their treasure.

If the coins were fake, made to look like gold, (like our own £1 coins- 70% copper, 5.5% nickel and 25.5% zinc) they would be hard. A real gold coin would be pleasingly soft to a pirate’s tooth!

Plate your own coins

Turn a penny ‘silver’ and then ‘gold’ with this nice experiment on alloys from the Royal Society of Chemistry.

Check out the video of it here:

Don’t try to use your coins to buy anything though: There are already lots of ways to check whether coins are fake or real and the Royal Mint has recently developed a new type of coin which is even more sophisticated and uses a secret ingredient in the alloy to give even more security. You can find out more in this BBC Wales News report (but the secret ingredient stays secret!)

If you fancy trying some of the techniques used to find out how much of different metals there are in alloys (like brass, bronze and steel) give this experiment (Key Stage 4+) a go.

Australian banknotes are made from polypropylene (photo: Martin Kingsley)

Australian banknotes are made from polypropylene. Photo: Martin Kingsley(CC-BY)

What about paper money? 

If you’re better at keeping hold of your cash than me you might have some paper money in your wallet.

In the UK our paper money is made out of cotton fibre and linen rag, the main component is cellulose. That makes it much tougher than normal paper from wood pulp but not nearly as tough as the ‘paper’ money found in Australia, Canada, Romania, Vietnam and New Zealand. The money in those countries is made of a plastic called polypropylene, a polymer.

Plastic money lasts much longer (which is better for the environment), is more secure (as extra safety features can be included) and can even survive a spin in the washing machine!

Plastic money could be coming to the UK too so you might want to find out more about how polymers work and how to identify them.  This experiment explores ways to identify different polymers, in this case different plastics.

 

Curriculum Links

Key Stage 3:

Pure and Impure Substances

  • mixtures

Materials

  • properties of polymers

Key Stage 4:

This science made simple blog intends to enrich, and give context to AQA GCSE Science CHEMISTRY 1 Unit C1.3.2 Alloys and Unit C.1.5.2 Polymers

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Posted in Chemistry