The Unknown Phase of Matter

Summary by Krater

Steve Mould explores the properties of super-critical fluids by building a transparent, high-pressure vessel to observe carbon dioxide transitioning between liquid, gas, and super-critical states.

From the video

Answers: What is a super-critical fluid and how does carbon dioxide behave at high pressure and temperature?

• super-critical fluids
• phase diagrams
• solid carbon dioxide sublimation
• liquid carbon dioxide density
• critical point
• thermodynamics and entropy

What it concludes

• At high pressure, solid carbon dioxide melts into liquid carbon dioxide instead of sublimating straight into a gas.
• In a sealed vessel at equilibrium, both liquid and gas phases can coexist with a meniscus as a boundary.
• Beyond the critical point, the distinction between liquid and gas disappears, forming a super-critical fluid with fluctuating density.
• Supercritical carbon dioxide retains low viscosity like a gas and solvent power like a liquid, making it useful for extracting caffeine from coffee beans.