* Hydrogen's phases: Hydrogen exists as a gas (H2) at room temperature and pressure. To transition from a gas to a liquid, it needs to be cooled significantly.
* Melting point: The melting point of hydrogen is extremely low, at -259.14 °C (-434.45 °F). It's so low that even a very cold environment wouldn't cause it to melt from a solid to a liquid.
* Direct phase change: When hydrogen is cooled below its melting point, it undergoes a direct phase change from a gas to a solid (a process called deposition). The solid form is called "solid hydrogen".
Therefore, hydrogen doesn't melt in the traditional sense. It transitions directly from a gas to a solid.
Note: While hydrogen can exist as a liquid at extremely low temperatures and pressures, it's not a common occurrence.
