Rust and Iron
A rusty "Children Playing" sign from Japan
You can easily see that iron rusts and turns red when oxygen touches it. Go look around your backyard or your neighborhood and try to find ten things that are made of iron and have rusted. You might check cars, fences, old toys or tools left in the yard, nails, and street signs. If you're working on this in school, you could bring in photos of these rusty things to make into a poster.
What happens when you rub on the rust? Can you rub it all off and make the iron shiny and black again?