Shrinking Balloon

Liquid nitrogen at 77 K can cause severe frostbite and cold burns on contact with skin. Always use tongs or insulated gloves when handling materials in contact with liquid nitrogen. Ensure adequate ventilation, as large amounts of boiling nitrogen can displace oxygen in poorly ventilated spaces.

When the balloon warms back up, it will rapidly re-expand. Keep the balloon contained or pointed away from people and equipment during the rewarming process. Do not seal frozen balloons in closed containers as pressure buildup during warming can cause rupture.

Purpose

Students observe Charles's Law ( $V \propto T$ at constant $$P$$ ) as a balloon shrinks dramatically in liquid nitrogen. Comparing balloons filled with air, CO $$_2$$ , and helium reveals both the ideal gas relationship and phase transitions at cryogenic temperatures.

Tan liquid nitrogen dewar with warning label, clear glass bowl, inflated dark green balloon, and metal tongs on a green benchtop

Collapsed dark green balloon submerged in glass bowl with tongs, next to the liquid nitrogen dewar

Figure 1: Equipment: 4L liquid nitrogen dewar, glass bowl, inflated balloon, and tongs for safe handling.

Figure 2: Balloon after cooling in liquid nitrogen, dramatically reduced in volume.

Warning: Cryogenic Hazard

Warning: Pressure Hazard

Purpose

Safety Warnings

Warning: Cryogenic Hazard

Warning: Pressure Hazard

Purpose