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Supported by Rolls-Royce

Polishing pennies

Make old pennies sparkle with some simple chemical reactions.
Plan a session with this activity

You will need

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


Before you begin

  • Set up three experiment stations with the necessary equipment:
    • one only using vinegar
    • one using vinegar and salt
    • one using vinegar and baking powder

Keep things safe

  1. Everyone should discuss how to keep themselves and others safe when conducting experiments like this one, which uses the power of chemical reactions for cleaning pennies. Highlight the importance of:
    • reading all warning labels on the materials being used
    • carefully following directions
    • wearing eye protection
    • wearing gloves
    • wearing protective clothing (such as a lab coat) or something with long sleeves
    • tying back long hair
    • keeping all chemicals away from your mouth, nose and eyes
    • not consuming any food or drink near an experiment.
  1. Everyone should make sure they are dressed suitably and safely.

Get ready to experiment

  1. Make some predictions about what might happen in the three experiments. What will happen when the penny touches the vinegar? How long will it take to see results? What will the chemical reactions between the salt, vinegar and baking powder look like? Which experiment will be most effective, and why?
  2. Everyone should split into three small teams. Each team should start at one of the experiment stations. Repeat the experiments three times so each team gets a go, or encourage everyone to record their findings and report back to the other teams.


Examine the results

  1. The teams should gather together with their pennies to discuss their results. What did you observe from your experiments? Are some pennies cleaner than others?
  2. Everyone should discuss what happened when salt or baking powder was added to the vinegar. Was a chemical reaction observed? What was it? (The baking powder caused the mixture to fizz as carbonic acid and sodium acetate were produced by the reaction.)
  3. Everyone should discuss how they think the vinegar cleaned the pennies. (Pennies are made from copper, which reacts over time with the oxygen in the air. This is called ‘oxidisation’, and makes the pennies look dull and dirty. Vinegar is also called acetic acid, and its acidity makes it able to strip off the copper oxide.)
  4. Everyone should discuss which vinegar mixture was the best at cleaning the pennies. Which came out the cleanest? (Adding salt or baking powder will strengthen the vinegar’s ability to remove the copper oxide.)
  5. Everyone should reflect on the predictions they made. Did any of them come true? Was anything surprising?


This activity was about learning new skills. Why might the cleaning power of vinegar be useful to know about? (It’s a household item that can be useful for cleaning lots of things, and isn’t harmful like other products). We made sure this experiment was done as safely as possible. Why was that important? What other experiments would you like to do?

This activity was also about problem solving. We all made predictions about what we thought might happen in the experiments. What led you to make those predictions? What did you learn from the ones that did and didn’t come true?



This task involves the use of potentially harmful fluids or chemicals. Make sure you follow all relevant safety guidance. Make sure you dispose of them appropriately too, in line with safety guidance.


Supervise young people, and only do science activities that are advised and age appropriate for your section. Test activities first, to make sure you’re confident you can lead them safely. Use protective clothing where necessary.

Ensure the vinegar solutions are disposed of carefully and that everyone washes their hands thoroughly after each experiment.

All activities must be safely managed. Do a risk assessment and take appropriate steps to reduce risk. Always get approval for the activity and have suitable supervision and an InTouch process.

Make it accessible

All Scout activities should be inclusive and accessible.