Is Hydrogen a flammable gas? (A comprehensive overview)

This article will give you the answer to the question “Is Hydrogen a flammable gas?” and it will explain to you what exactly hydrogen gas is. The article will also help you to understand the importance of hydrogen gas, its properties and its uses.

Is Hydrogen a flammable gas?

Yes, hydrogen is an extremely flammable gas. It is the simplest and lightest chemical element. It is a tasteless, odorless and colorless gas.

The symbol, atomic number and atomic mass of hydrogen are given below:

  • Symbol: H
  • Atomic number: 1
  • Atomic mass: 1.00794 g/mol

Discovery of Hydrogen

The reaction between iron filings and dilute acids was detected and described by Robert Boyle in 1671. This led to the formation of hydrogen gas. However, a century later Henry Cavendish recognized hydrogen as a distinct substance during a metal acid reaction.

Hydrogen (as a chemical element)

Hydrogen is the first element in the periodic table which means that hydrogen is the lightest and most abundant element in the universe. The atomic number of an element denotes the number of electrons present in it. Since hydrogen has two electrons in total, the atomic number of hydrogen is 1. 

Physical Properties of Hydrogen

The physical properties of hydrogen are given below:

  • The boiling point of hydrogen is −252.879 °C
  • The melting point of hydrogen is  ​−259.16 °C
  • The density of hydrogen is 0.08988 g/L at standard temperature and pressure (STP)
  • The triple point of hydrogen is 13.8033 K, ​7.041 kPa
  • The critical point of hydrogen is 32.938 K, 1.2858 MPa
  • The heat of vaporization of hydrogen is 0.904 kJ/mol 
  • The heat of fusion of hydrogen is 0.117 kJ/mol
  • The molar heat capacity of hydrogen is 28.836 J/(mol·K)

Phases of Hydrogen

Phases of an element consist of regions in which they have essentially the same physical properties. Hydrogen can be seen in the following phases:

  • Solid hydrogen
  • Liquid hydrogen
  • Gaseous hydrogen
  • Plasma hydrogen
  • Slush hydrogen
  • Metallic hydrogen

Solid Hydrogen:

In this phase, hydrogen is in a solid state with a density of  0.086 g/cm3. It is one of the solids with the lowest density. The solid state of hydrogen can be obtained by reducing its temperature below its melting point.

Liquid Hydrogen:

In this phase, hydrogen is in a liquid state, which means that it possesses the ability to flow. The liquid state of hydrogen can be obtained by reducing its temperature (approximately −252.87 °C). This state can also be achieved by compressing the gaseous form of hydrogen.

Gaseous Hydrogen:

In this phase, hydrogen is in a gaseous state. This is the most common state of hydrogen. It is invisible, colorless, odorless and tasteless.

Plasma Hydrogen:

In this phase, hydrogen is in a plasma state, which means that it comprises a gas of ions. Hence it has an electric charge. It also acts as a reducing agent that has the potential to eradicate oxides from metal surfaces.


Slush Hydrogen:

In this phase, hydrogen exists as a combination of both solid and liquid phases. It is formed when repeated cycles of increasing hydrogen’s temperature to its boiling point and then decreasing its pressure. Compared to liquid hydrogen, slush hydrogen has a much lower temperature and higher density. 

Metallic Hydrogen:

In this phase, hydrogen acts as a conductor of electricity. Although hydrogen is not a metal, it forms diatomic molecules of hydrogen. These diatomic molecules are liquid in form under normal conditions but they solidify at low temperatures. In such cases, hydrogen behaves like a metal when subjected to immense pressure (approximately 25 GPa)

Isotopes of hydrogen 

Isotopes are nothing but different forms of the same element. For example, the number of protons will be the same in each of the forms but the number of neutrons will vary from one form to another. Hydrogen has three isotopes that occur naturally, they are:

  • Hydrogen 
  • Deuterium
  • Tritium


This is the first isotope of hydrogen and can be simply called “hydrogen”. This isotope consists of one proton and does not have any neutrons.


This is the second isotope of hydrogen. This isotope consists of one proton and has one neutron. In total, there are two nucleons, hence the name deuterium.


This is the third isotope of hydrogen. This isotope consists of one proton and has two neutrons. In total, there are three nucleons, hence the name tritium.

Flammability of Hydrogen 

Hydrogen is an extremely flammable gas. It can cause severe explosions if not handled with care. The fires caused due to hydrogen explosions are unseeable. Also, hydrogen leakages are difficult to detect as it is colorless and odorless. 

The enthalpy of combustion of hydrogen gas is −286 kJ/mol. When hydrogen comes in contact with air (oxygen), it yields water along with a huge amount of energy dissipated in the form of heat. The chemical reaction is given below:

2 H2(g) + O2(g) → 2 H2O(l) + 572 kJ

Uses of Hydrogen

Hydrogenation Reactions

The reaction of hydrogen with any other compound to saturate or decrease its form in the presence of a catalyst is called hydrogenation. Hydrogenation reactions are used for various purposes such as hydrogenation of unsaturated fats, hydrogenation of nitrogen gas, hydrogenation of carbon dioxide, etc.

Hydrogenation of unsaturated fats:

Unsaturated fats and oils are converted to saturated ones by hydrogenation. The production of margarine is one of the most common examples of this.

Hydrogenation of nitrogen gas:

The hydrogenation of nitrogen gas to produce ammonia is done by a process called Haber Process which fixes nitrogen in an artificial manner. A large portion of the protein consumed by humans comes from ammonia formed from this method.

Hydrogenation of carbon dioxide:

Methanol or methyl alcohol is a volatile liquid that is obtained by the hydrogenation of carbon dioxide. In this process, hydrogen gas formed during water decomposition bonds with the carbon dioxide on the surface of the catalyst to create methanol.

Hydrogen as a coolant

Although hydrogen is a highly flammable gas, it is commonly used as a coolant or a refrigerant. Due to their unique properties, hydrogen is used as a coolant in generators. For example, gaseous hydrogen is used as the coolant in a turbo generator.

Hydrogen in the semiconductor industry

Stabilizing material properties is made possible by saturating broken silicon and carbon bonds with hydrogen. This is commonly used in the semiconductor industry. 


This article addresses the question “Is Hydrogen a flammable gas?” 

The article has given a comprehensive overview of hydrogen gas and its flammability. The article has also given information about the physical properties, phases and uses of hydrogen gas.

Please do not hesitate to comment on the above content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): Is Hydrogen a flammable gas?

Does hydrogen catch fire? 

Yes, hydrogen does catch fire. It is an extremely flammable gas and reacts quickly.

Can hydrogen gas explode? 

Yes, hydrogen gas can explode as it is a highly flammable gas. It takes a relatively small amount of energy to ignite a small amount of hydrogen (especially liquid form) when combined with air

Is hydrogen harmful for human health?

Yes, can be quite harmful for humans especially when inhaled. It can cause severe headaches, nausea, unconsciousness and in general, a reduction in all the senses.

Can you burn hydrogen without oxygen?

No, you cannot burn hydrogen without oxygen. For a fire to exist, a chemical reaction of the following elements are crucial. They are:

  • Oxygen
  • Heat
  • Fuel


What was missing from this post which could have made it better?

Leave a Comment