at what temperature does hydrogen become a liquid
Liquid hydrogen To exist as a liquid, H2 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[3] (−423.17 °F/−252.87 °C).[4][5] 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.
Viscosity The dynamic viscosity of water is 6996890000000000000♠8.90×10−4 Pa·s or 6997890000000000000♠8.90×10−3 dyn·s/cm2 or 0.890 cP at about 25 °C.