Final answer:
Placing a balloon in liquid nitrogen does not constitute an adiabatic process because heat transfer occurs. The light blue liquid is likely liquefied oxygen, and the crystals are probably frozen nitrogen or other gases in the air.
Step-by-step explanation:
During a physics classroom demonstration where an instructor places an inflated balloon into liquid nitrogen, it is common to observe the balloon shrinking and then re-expanding upon warming. The process of placing a balloon into liquid nitrogen is not considered adiabatic because thermal energy is transferred between the balloon and the liquid nitrogen. Adiabatic processes are defined as those where no heat is transferred into or out of the system, as stated in the principles of thermodynamics.
The blue liquid observed within the cooled balloon is likely condensed oxygen, which has a pale blue color when liquefied. The snow-like crystals may be frozen nitrogen or other gases present in the balloon's air. Upon warming, the liquids boil, and some crystals sublimate, turning directly from a solid to a gas without becoming liquid first. Some crystals producing liquid again are indicative of the phase changes occurring as the balloon's temperature increases back to room temperature.