What Causes the ‘Rust’ on Old Coins?

Coins turn red when they meet water and air. It’s like when you leave a metal spoon in the sink for too long, it starts to look rusty! Over time, the coin reacts with oxygen in the air and water, making it change color from shiny silver to a rusty red. This is called oxidation, and it happens slowly, just like how apples turn brown when they’re left out.

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Examples

  1. A penny left in a jar with water turns reddish over time.
  2. An old nickel becomes dull and rusty after sitting on the kitchen table for years.
  3. Coins buried under dirt in a treasure hunt look like they've been through fire.

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Categories: Science · coins· chemistry· oxidation· rust· metals