The coldest known gas is a form of hydrogen called molecular hydrogen (H2) when it is cooled to near absolute zero. At this extreme temperature, the gas exhibits unique properties and behaviors that differ significantly from its warmer counterpart.
To put it into perspective, absolute zero is 0 Kelvin, or about -273.15 degrees Celsius (-459.67 degrees Fahrenheit). When hydrogen gas is cooled to these temperatures, it enters a state where quantum effects become pronounced, and its molecules slow down dramatically, leading to almost no thermal energy.
This phenomenon is often studied in laboratories to understand various quantum mechanical effects. It’s important to note that while hydrogen is not the only gas that can be cooled to these temperatures, it is one of the simplest and most researched.