Liquid Nitrogen Banana Hammer

A banana frozen in liquid nitrogen becomes so hard that it can be used like a hammer to drive a nail into wood.

1. Put on safety glasses and cryogenic gloves.
2. Place a banana into a container of liquid nitrogen and allow it to freeze solid.
3. Using tongs, remove the frozen banana from the liquid nitrogen.
4. Hold the banana firmly and attempt to hammer a nail into a piece of soft wood.
5. Observe that the banana is hard enough to act like a hammer.

The banana hammer experiment - BOC South Pacific:

• Try freezing other fruits or vegetables (carrots, cucumbers, or apples) and test their hardness.
• Compare how a fresh banana bends versus how a frozen banana shatters when struck.

• Safety glasses required.
• Wear cryogenic gloves when handling liquid nitrogen and the frozen banana.
• Use tongs to place and remove the banana from liquid nitrogen.
• Do not eat the banana (ingesting liquid nitrogen can be fatal).
• Only hammer into soft wood to prevent splinters or shattering of the banana.
• Ensure demonstration area is dry and non-slippery, as nitrogen fog can create condensation.

• Why does a banana, normally soft, become hard enough to hammer a nail?
• How does liquid nitrogen change the physical properties of organic materials?
• What happens at the molecular level when water inside the banana freezes so quickly?
• Why does the frozen banana shatter more easily compared to a fresh one?
• How could this principle be applied in real-world material testing or engineering?