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Description

Make old pennies sparkle with some simple chemical reactions.

Courtesy of The Scout Association
https://www.scouts.org.uk/activities/polishing-pennies/

Resources

Old pennies
White wine vinegar
Salt
Baking powder
Non-metallic spoons
Non-metallic bowls
Paper towels

See video at https://www.scouts.org.uk/activities/polishing-pennies/


REMEMBER TO DISCUSS SAFETY WHEN USING CHEMICALS


Take it further
- Create more copper cleaning solutions by using different acidic liquids. While vinegar contains acetic acid, lemon juice contains citric acid and coca cola contains phosphoric acid. Repeat this experiment using lemon juice and coca cola to explore which liquid, when reacted with salt, is best at removing copper oxide.

- The best liquid will be the one will the lowest pH number. The pH scale measures how much acid is in a solution, and the lower this number is, the more acidic it is. Depending on the vinegar, its pH is likely to measure between 2.4 and 4.5. Coca Cola generally comes in lower, at about a 2.5 pH. Lemon juice is the most acidic of all, with a pH of about 2.

Instructions

RECOMMENDED: See PDF instructions attached; or
ALTERNATIVE: continue below for a version adapted from the Scouts webpage

Experiment station: vinegar
One member of the team should pour enough vinegar into two bowls to form a shallow puddle.
Add salt to one of the bowls.
Another member should fill a third bowl with water.
Use a spoon to carefully place several pennies in the vinegar. Don’t overcrowd the bowl with pennies. Make sure each one is fully submerged.
Leave the pennies to sit in the bowl for between 10 and 30 seconds. As the pennies soak, you should notice the dirt melting away from them. Gently shake the bowl to remove even more of the dirt.
One member of the team should use a spoon to remove the pennies from the vinegar and put them into the bowl of water.
Everyone should use their hands to get the last of the grime off the pennies.
Once they are clean, everyone should take the pennies out of the water and place them on paper towels to dry.
Record your observations.
Repeat the experiment with the salt &vinegar bowl.
Record your observations
Compare the two experiments. Which one cleaned the coins best and why?

Answer: vinegar is an acid with a ph between 2&4 depending on the vinegar used. Salt is neutral(ph 7 usually) but it speeds up the oxidising process that removes the dirt from the coins.

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Badge Links

• Experiment - Experiment
• Scientist - Vinegar