If you like us, please share us on social media, tell your friends, tell your professor or consider building or adopting a Wikitext for your course.
The volume of the balloon significantly decreases. When the balloon is removed from the liquid nitrogen, it regains its volume.
A gas expands when heated and condenses when cooled. Charles' Law predicts a four-fold decrease in the volume of a gas that is cooled from room temperature to the temperature of liquid nitrogen (77 K). If the gas inside the balloon condenses into a volatile liquid at or around 77 K, the volume change will be even larger.
Removing the balloon exposes the cold balloon to higher temperatures. The resulting thermal expansion fills the balloon to its original size again.