Posts tagged: lemons

Fruit – Polishing Pennies (Weekly Unplugged Project)

By , September 29, 2008 3:53 am

This week’s Unplugged Project theme was fruit.  We tried a really cool fruit project that was less than successful.  I would have posted about our failure, except that I KNOW it can succeed since I did it successfully as a child.  It needs a bit more fiddling (so we’ll keep working and post when it is perfected).

Instead I’ll post about a fruit science project from our book 730 Easy Science Experiments: With Everyday Materials.  My oldest daughter found this in the book last week and for some reason was desperate to do it: polishing pennies. (I reviewed this book here if you want to know more.)

The idea is to show how lemon juice (very acidic) can clean the oxidization off a grungy old penny. If you live outside the US, any copper coin will work for this.

We ratcheted this one up.  I had always heard that Coca Cola was acidic enough to strip enamel off teeth and polish stainless steel sinks, so a comparison test seemed in order.  I had a Coke in the fridge from leftover guests so we gave it a go.

I was hoping that the Coke might perform up to the standard of the lemon juice and prove once and for all that it is BAD for your teeth.

Here are the ingredients:

Squeeze the lemon (pretty fun):

Put some lemon juice (and some Coke-if you choose to try the comparison experiment) into separate bowls and drop pennies into each bowl:

Leave them for 15 or 20 minutes then remove and compare:

We probably should have kept a “control penny” for comparison (actually, you can see the originals in the “ingredients” photo) but trust me, the lemon juice pennies were like new!  The Coke pennies only slightly shinier.  So much for my anti-Coke campaign.


What did you do this week for fruit? If you joined in this week’s fruit project, then please leave a link to your project in Mr. Linky below. If you want to learn how to join in the Unplugged Project, then please read more here.


Next week’s Unplugged Project theme will be:



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