<Tr> <Td> </Td> <Td> </Td> </Tr> <P> Liquid hydrogen (LH2 or LH) is the liquid state of the element hydrogen . Hydrogen is found naturally in the molecular H form . </P> <P> To exist as a liquid, H must be cooled below hydrogen's critical point of 33 K . However, for hydrogen to be in a fully liquid state without boiling at atmospheric pressure, it needs to be cooled to 20.28 K (− 423.17 ° F / − 252.87 ° C). One common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle . Liquid hydrogen is typically used as a concentrated form of hydrogen storage . As in any gas, storing it as liquid takes less space than storing it as a gas at normal temperature and pressure . However, the liquid density is very low compared to other common fuels . Once liquefied, it can be maintained as a liquid in pressurized and thermally insulated containers . </P> <P> There are two spin isomers of hydrogen; liquid hydrogen consists of 99.79% parahydrogen and 0.21% orthohydrogen . </P>

At what temperature does hydrogen become a liquid