Finding Absolute Zero

Liquid nitrogen and dry ice can cause severe frostbite on contact. Always wear insulated gloves when handling these materials. Ensure adequate ventilation as both liquid nitrogen and dry ice produce large volumes of gas that can displace oxygen. Never seal cryogenic liquids in closed containers.

Use caution around the hot plate and boiling water. Position the demonstration where students cannot accidentally contact hot surfaces. Turn off the hot plate when not actively taking measurements.

Purpose

Measure gas pressure at four known temperatures and plot pressure vs. temperature to experimentally determine absolute zero by linear extrapolation. Provides a concrete foundation for the Kelvin scale and Gay-Lussac's Law.

Gas thermometer with copper spherical bulb, brass stem, Winsco gauge reading -60 to 60 cm Hg, brass valve with hose barb, and black handle

Gas thermometer copper bulb submerged in boiling water in a large glass beaker on a Thermolyne hot plate, hand holding the black handle

Gas thermometer bulb submerged in ice-water mixture in a large glass beaker, hand holding handle, gauge reading near -20 cm Hg

Figure 1: Gas thermometer assembly: copper bulb (gas reservoir), brass connecting tube, Winsco gauge calibrated in cm Hg, and valve for pressure equilibration.

Figure 2: Measuring gauge pressure with the copper bulb submerged in boiling water on a hot plate.

Figure 3: Measuring gauge pressure with the bulb submerged in an ice-water bath at 0°C.

Warning: Cryogenic Hazards

Warning: Boiling Water

Purpose

Safety Warnings

Warning: Cryogenic Hazards

Warning: Boiling Water

Purpose