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A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. Thus, as energy in the form of heat is added, a solid (e.g. ice) will first melt to become a liquid (e.g. water), which will then boil or evaporate to become a gas (e.g. water vapor). In some circumstances, a solid (e.g. "dry ice") can directly turn into a gas: this is called sublimation. If the gas is further heated, its atoms or molecules can become (wholly or partially) ionized, turning the gas into a plasma.

Physics


In the gas phase, the atoms or molecules constituting the matter basically move independently, with no forces keeping them together or pushing them apart. Their only interactions are rare and random collisions. The particles move in random directions, at high speeds, whose range is dependent on the temperature and defined by the Maxwell-Boltzmann distribution. Therefore, the gas phase is a completely disordered state. Following the second law of thermodynamics, gas particles will immediately diffuse to homogeneously fill any shape or volume of space that is made available to them.

The thermodynamic state of a gas is characterized by its volume, its temperature, which is determined by the average velocity or kinetic energy of the molecules, and its pressure, which is determined by the average velocity and density or number of molecules. These variables are related by the fundamental gas laws, which state that the pressure in an ideal gas is proportional to its temperature and number of molecules, but inversely proportional to its volume.

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CORGI Gas - CORGI oversees the safety of gas installations. Provides some information about the law and a facility to check installers' registrations.

ELEXON - Balancing and settlement code company, manages the electricity and trading arrangements of England and Wales. Details of panel, signatories, papers and other information.
Meta Description: [ The public website of Elexon Ltd ]

Energywatch - Energywatch represents the interests of gas and electricity consumers in Great Britain. Provides practical information for consumers and some policy documents.
Meta Description: [ Energywatch - your gas and electricity watch dog ]

Health and Safety Executive - Downstream gas - The HSE oversee safety regulation in downstream gas. Includes codes of practice, incident reports, and information for the industry.
Meta Description: [ Health and Safety for domestic gas consumers and the gas supply industry ]

Health and Safety Executive - Offshore oil and gas - HSE pages relating to the regulation of safety cases for offshore gas platforms.
Meta Description: [ Provides occupational health and safety information for the offshore oil and gas industry ]

Joint Office of Gas Transporters - Responsible for the governance of gas industry-wide arrangements and codes, particularly the Uniform Network Code. Full code text available (PDF).
Meta Description: [ The Joint Office of Gas Transporters has been created as part of the distribution network sales process which has been overseen by Ofgem ]

Nuclear Safety Directorate - Part of the Health and Safety Executive responsible for the safety regulation of the civilian nuclear industry. Some policy documents and a variety of reports on cases.
Meta Description: [ Information about, and the work of, HSE's Nuclear Safety Directorate ]

Office for the Regulation of Electricity and Gas - Ofreg or NIAER. Regulates the electricity and gas markets in Northern Ireland. Consultation and decision documents.

Office of Gas and Electricity Markets - Ofgem. Regulates the electricity and gas markets in Great Britain. All consultation and decision documents, and many consultation responses from regulated companies and other organisations.

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