Some pennies are mostly copper and some pennies are mostly zinc. What happens to the different materials when they are cooled with liquid nitrogen and then hit with a hammer?
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: And this is a container of liquid nitrogen!
Steve: And this is a cup with a bunch of pennies in it!
Joanna: And just like any normal person would do in this situation, we're going to mix the nitrogen with the pennies!
Steve: While all pennies look more or less alike, there's a big difference between newer pennies and older pennies. Older pennies are made mostly out of copper, but newer pennies are made mostly out of zinc. They just look like copper because they have a thin copper plating on them. The transition between copper pennies and zinc pennies happened in 1982.
Joanna: There's also a big difference between copper and zinc when they get cold. Copper doesn't mind so much. I can hit an older penny with a hammer, and nothing really bad happens.
Zinc, however, gets really brittle when it's cold. If I hit a newer penny with a hammer, it shatters!
Thanks for watching! I hope you'll join us again soon for another experiment!
Steve: Okay, so which of these pennies are mine again?
Joanna: The zinc ones!
Steve: The zinc ones?
Joanna: These are for you.
Joanna: These are mine!
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