Can Ketchup Clean a Penny?

Squeaks loves collecting shiny pennies, but sometimes he finds one that's sort of grimy and dull. Lucky for him, Jessi knows a really cool science trick to clean up those tarnished pennies!
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buggyandbuddy.com/science-for-...
www.exploratorium.edu/science...
playfullearning.net/2012/06/si...
chemistry.stackexchange.com/q...
cleaning.lovetoknow.com/Penny_...
applenetwork.us/experiments/Vi...
water.usgs.gov/edu/ph.html