This science trick is so easy, you can do it in a fast food restaurant.
First, grab some ketchup and salt packets and some napkins. Squirt the ketchup on the napkin (you may need more than 1 napkin because the cheaper ones tend to break apart, and you don’t want to be stuck with ketchup on your hands!) and sprinkle a generous amount of salt on top. Then add your penny to the mix and fold the napkin around it. Rub the penny in the salt/ketchup mixture for about a minute, and then check on your results. Your penny should look close to new!
If you want to take this experiment a bit further, you can ask your kid, what is going on here? What do you think the salt does? How do you think the ketchup cleans up the penny? Are there any other condiments that could work too? Before you answer their questions, have them try their own experiments to see what happens.
The reason that the penny shines up with ketchup and salt is mainly because the ketchup contains vinegar (a.k.a. acetic acid). If you’re the kind of person who uses vinegar as a cleaning product, you’re probably already aware of its versatility. One of my favorite things to use it for is to clean a dirty showerhead. Other condiments contain vinegar too, such as mustard or pickle brine. The reason for the salt is that it acts as an abrasive and cleans the penny quicker than ketchup alone. Although, you could probably just leave the penny in the ketchup for a few hours and it probably would have the same effect. In fact, as a followup experiment, why don’t you try that with your kids too?
If you have a favorite science experiment, leave it in the comments!