Is Hydrogen a Solid, Liquid or Gas? (+ 3 Things to Know)

Hydrogen is a gas at standard temperature and pressure (STP). It becomes a liquid at -252.87°C and a pressure of 1 atmosphere, and it solidifies at a temperature of -259.14°C and a pressure of 1 atmosphere. ^{1 2}

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Why does hydrogen exist as a gas at room temperature?

Hydrogen exists as a gas at room temperature because it has a low boiling point and low molecular weight.

The boiling point of hydrogen is -252.87°C (-423.17°F), which is extremely low compared to other elements, such as oxygen and nitrogen, which exist as gases at room temperature but have much higher boiling points (-183°C and -196°C, respectively). ^{3 4}

This means that hydrogen requires very little energy to transition from a liquid to a gas, which allows it to exist as a gas at room temperature.

Additionally, hydrogen (H2) has a very low molecular weight (2 atomic mass units), which means that the intermolecular forces between hydrogen molecules are very weak. ⁵

As a result, hydrogen molecules do not tend to clump together and form a liquid at room temperature, but instead remain as individual gas molecules that move freely and rapidly in the air.

Overall, the combination of a low boiling point and low molecular weight allows hydrogen to exist as a gas at room temperature.

Does hydrogen exist in liquid or solid state?

Yes, hydrogen can exist in liquid and solid states under certain conditions of temperature and pressure.

At standard pressure, hydrogen only exists as a gas at temperatures above its boiling point of -252.87°C (-423.17°F).

However, if hydrogen is subjected to very high pressures, it can be compressed into a liquid state at temperatures below its boiling point. This liquid hydrogen is used as a rocket fuel due to its high energy content. ^{6 7}

Moreover, hydrogen can also exist in a solid state at extremely low temperatures and high pressures. ⁸

Solid hydrogen can occur in two forms: orthohydrogen and parahydrogen, which have different physical properties. The transition from liquid to solid hydrogen occurs at a temperature of around -259°C (-434°F) under atmospheric pressure.

However, creating and maintaining these extreme conditions required to observe hydrogen in its liquid and solid states is challenging and requires specialized equipment.

How is gaseous hydrogen different from solid hydrogen and liquid hydrogen?

Gaseous hydrogen, solid hydrogen, and liquid hydrogen differ in their physical properties and behavior.

In the gaseous state, hydrogen exists as individual molecules that move freely and rapidly in the air.
Gaseous hydrogen is very light and has a low density, which makes it highly compressible and difficult to store in large quantities. However, it is also highly reactive and has a wide range of applications, such as in fuel cells and combustion engines. ^{9 10}

In the liquid state, hydrogen molecules are much closer together and move more slowly than in the gaseous state.
Liquid hydrogen has a density that is only slightly higher than that of gaseous hydrogen, but it is much more energy-dense and can be stored in tanks.
Liquid hydrogen is used as a rocket fuel and in other applications that require a high energy density, such as in some fuel cell systems.

In the solid state, hydrogen molecules are arranged in a crystal lattice and exhibit very different physical properties from gaseous or liquid hydrogen.
Solid hydrogen has a very low density and is an excellent thermal insulator. ¹¹ Additionally, it exhibits unique quantum mechanical properties due to its low mass and simple molecular structure.
However, the creation and maintenance of solid hydrogen requires extremely low temperatures and high pressures, making it difficult to study and utilize.

Overall, gaseous, liquid, and solid hydrogen differ in their physical properties and behavior due to differences in the molecular arrangement and energy of the hydrogen molecules.

Further reading

Why is Hydrogen a Nonmetal?
Is Phosphorus a Solid, Liquid or Gas?
Is Sodium a Solid, Liquid or Gas?
Is Oxygen Solid, Liquid or Gas?
Is Lithium Solid, Liquid or Gas?

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