Simple Science
Penny cleaning
Direction
You will need
1. 60 ml of White
vinegar
2. Dull Pennies
3. 1 teaspoon of
salt
4. Glass or plastic
ball
5. Steel nail or
screw
1. Mix the salt and the vinegar in the bowl
2. Shiny Pennies
1. Drop a penny into the bowl (or for a better effect hold half of the
coin in the mixture)
2. After 20 seconds lift the coins out
3. Rinse and dry penny
4. Add as many pennies as possible (although it’s probably sensible
to add no more than 20)
5. Wait for 5 minutes
3. Colour changing Pennies
1. Remove half of the pennies from the bowl
2. Place these pennies on the paper towel
3. Remove the other pennies, rinse them thoroughly and then leave
them to dry on the paper towel
4. Leave both sets of pennies for an hour
4. How to bling up your nails
1. Place the nail/screw into the vinegar salt mix
2. After 20 minutes check the colour of the nail (if not try again after
an hour)
What’s going on?
The first part of this experiment uses the acid (vinegar) and the salt
mixture to dissolve the copper oxide on the surface of the coins. The
copper on the surface of the coins reacts with oxygen forming copper
oxide which has a dull colour. The copper oxide remains in the vinegar
solution.
In the second part of the experiment the green substance, which should
be visible on the coins after an hour, is known as Verdigris. Vedigris is
produced from the reaction of the copper and the salt and vinegar (left
on the coins from the salt and vinegar solution) with the oxygen. The
coins that were rinsed with water, and which are not covered by the salt
and vinegar solution should look nice and shiny.
The copper oxide which was has been dissolved from the surface of the
coins is in the salt and vinegar solution. It is a positively charged particle
(known as an ion). When you place the nail in the solution, the iron
oxides on the surface of the nail are dissolved and the surface of the nail
becomes negatively charged. The positively charged copper oxide is
attracted to the nail more strongly than the iron oxides, and so the
copper bonds with the surface of the nail. Did you see bubbles around
the nail when you put the nail into the vinegar? These were bubbles of
hydrogen which was formed from reactions between the acid and the
metal (copper or iron) oxides.
Centre for Lifelong Learning
Alex Brown, 2012
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