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Methane

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Methane is a fundamental chemical compound used widely across the globe. Its chemical formula is CH4. This means it consists of one carbon atom bonded to four hydrogen atoms.

Covalent
Covalent

As the simplest alkane, it is the primary component of natural gas. This makes it an economically important fuel for many industries. Methane is an organic hydrocarbon, which is a type of organic compound. It exists as a colorless and odorless gas at standard temperature and pressure. Because it is hard to store as a gas, it is often transported as a liquid. This liquid form is known as liquefied natural gas, or LNG.

The structure of a methane molecule is quite specific. It is a tetrahedral molecule. This means the four hydrogen atoms are arranged around the central carbon atom in a shape like a pyramid with a triangular base.

Covalent
Covalent

The bonding involves the overlap of molecular orbitals. The lowest-energy orbital comes from the overlap of the carbon 2s orbital with the 1s orbitals of the four hydrogens. Above this, there is a set of three higher-energy orbitals. These involve the overlap of carbon 2p orbitals with the hydrogen 1s orbitals. This specific "three-over-one" bonding scheme is confirmed by scientists using photoelectron spectroscopy.

Methane is produced through various natural processes on Earth. It can be formed by geological processes deep within the planet. It is also created by biological processes.

Origins of Biotic and Abiotic Methane
Origins of Biotic and Abiotic Methane

Some methane is found under the seafloor. The largest reservoir of this gas is held in the form of methane clathrates. These are ice-like structures found under the seafloor.

Frozen Methane Bubbles (11927906233)
Frozen Methane Bubbles (11927906233)

When methane moves from the ground into the air, it becomes atmospheric methane. This gas plays a major role in our climate. It is transparent to visible light, but it absorbs infrared radiation. This absorption makes it a potent greenhouse gas.

Human activities have significantly changed the amount of methane in our atmosphere. Since the year 1750, atmospheric methane concentrations have risen by approximately 160%. The vast majority of this increase is caused by human activity.

Global Methane Budget 2017
Global Methane Budget 2017

According to a 2021 report from the Intergovernmental Panel on Climate Change (IPCC), methane accounted for 20% of the total radiative forcing from all long-lived greenhouse gases. Radiative forcing refers to the change in energy balance in the atmosphere. Reducing methane emissions is considered a way to limit near-term warming. It can also improve air quality by reducing global surface ozone.

Sources of methane emissions, 2021
Sources of methane emissions, 2021

Methane undergoes several important chemical reactions. One major reaction is combustion, which is the process of burning. When methane burns, it releases energy. The heat of combustion for methane is 55.5 MJ/kg.

The fire within her
The fire within her

Another process is steam methane reforming, or SMR. This is the standard industrial method for producing hydrogen gas. In this process, methane reacts with steam at high temperatures, between 700 and 1100 °C. This reaction requires a metal catalyst, usually nickel. It produces a mixture of carbon monoxide and hydrogen, known as syngas.

Diagram of sustainable methane fuel production-en
Diagram of sustainable methane fuel production-en

This hydrogen is used in petroleum refineries and for making ammonia.

Methane is also vital for space exploration. It is used as a rocket propellant when combined with liquid oxygen. Engineers call this combination "methalox."

PIA19088-MarsCuriosityRover-MethaneSource-20141216
PIA19088-MarsCuriosityRover-MethaneSource-20141216

Using methane offers several advantages over other fuels like kerosene. It produces smaller exhaust molecules, which reduces soot buildup in the engine. Methane is also easier to store than liquid hydrogen. This is because it has a higher boiling point and higher density. Many modern rocket engines, such as the Raptor and the BE-4, use methalox. Future launch vehicles like Starship and New Glenn are also designed to use this fuel.

Beyond Earth, methane is a subject of great interest in astrobiology. Methane has been detected on other planets, including Mars.

PIA19088-MarsCuriosityRover-MethaneSource-20141216
PIA19088-MarsCuriosityRover-MethaneSource-20141216

Finding methane in space can provide clues about potential biological activity. We also see the visual effects of methane in our solar system. On the planets Uranus and Neptune, methane in the atmosphere absorbs red light.

PIA22481-SaturnMoon-Titan-Lakes-20170911
PIA22481-SaturnMoon-Titan-Lakes-20170911

This absorption causes these planets to appear blue or bluish-green. From the deep oceans of Earth to the distant reaches of space, methane is a molecule that connects many different worlds.

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🖼️ Images & Media (13)
File:Covalent.svg
Covalent.svg
File:The fire within her.jpg
The fire within her.jpg
File:Global Methane Budget 2017.jpg
Global Methane Budget 2017.jpg
File:Origins_of_Biotic_and_Abiotic_Methane.jpg
Origins_of_Biotic_and_Abiotic_Methane.jpg
File:CSIRO ScienceImage 1898 Testing Sheep for Methane Production.jpg
CSIRO ScienceImage 1898 Testing Sheep for...
File:The Creation of Methane Within a Ruminant.svg
The Creation of Methane Within a Ruminant.svg
File:Frozen Methane Bubbles (11927906233).jpg
Frozen Methane Bubbles (11927906233).jpg
File:Diagram of sustainable methane fuel production-en.svg
Diagram of sustainable methane fuel...
File:Sources of methane emissions, 2021.jpg
Sources of methane emissions, 2021.jpg
File:Abatement potential of policy measures, 2021.jpg
Abatement potential of policy measures, 2021.jpg
File:PIA19088-MarsCuriosityRover-MethaneSource-20141216.png
PIA19088-MarsCuriosityRover-MethaneSource-...
File:PIA22481-SaturnMoon-Titan-Lakes-20170911.jpg
PIA22481-SaturnMoon-Titan-Lakes-20170911.jpg

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