Gas

An illustration of the random way gas molecules move, without being attached to each other.

A gas is one of the four most common states of matter. In a gas the molecules move freely and are independent of each other. This makes it different from a liquid where the molecules are loosely attached. It is also different from a solid where the bonds are strong and hold the molecules together.

In a pure gas, each molecule may be made of an individual atom. It may be elemental, where each molecule is made of more than one of the same atom bound together. It may be compounds where molecules are made of many types of atoms together. An example of a monoatomic gas is neon, an example of an elemental gas is hydrogen and an example of a compound gas is carbon dioxide.

A gas mixture contains a mix of any of the above types, for example air which is 78% nitrogen, 20% oxygen and 2% argon and carbon dioxide.[1]

Poison gases were used as chemical weapons in World War I but were later banned. Natural gas is a natural mixture of methane and other gases.

Physical Characteristics

All gases can flow, like liquids. This means the molecules move about independently of each other. Most gases are colourless, like hydrogen.[2] Gas particles will spread about, or diffuse, in order to fill all the space in any container such as a bottle or a room. Compared to liquids and solids, gases have a very low density and viscosity. We cannot directly see most gases since they aren't coloured. However it is possible to measure their density, volume, temperature and pressure.

Pressure

Pressure is the measure of how much pushing force something is putting on another object. In a gas, this is usually the gas pushing on the container of the object or, if the gas is heavy, something inside the gas. Pressure is measured in pascals. Because of Newton's third law, we can change the pressure of a gas by putting force on the object containing it. For example, squeezing a bottle with air inside pressurises (gives more pressure) to the air inside.

When talking about gas, pressure is often related to the container. A lot of gas in a small container would have very high pressure. A small amount of a gas in a big container would have low pressure. Gas can create pressure itself when there is a lot of it. The weight of the gas creates pressure on anything underneath it, including other gas. On a planet, this is called atmospheric pressure.

Temperature

The temperature of a gas is how hot or cold it is. In physics it is usually measured in kelvins although degrees Celsius are more used elsewhere. In a gas, the average velocity (how fast they move) of the molecules is related to the temperature. The faster the gas molecules are moving, the more they collide, or smash into each other. These collisions release energy, which in a gas comes in the form of heat. Conversely if the temperature around the gas becomes hotter then the gas particles will convert the thermal energy to kinetic energy, making them move faster and making the gas hotter.[3]

Other Languages
Afrikaans: Gas
Alemannisch: Gas
Ænglisc: Lyft
العربية: غاز
aragonés: Gas
asturianu: Gas
Avañe'ẽ: Mba'etĩ
azərbaycanca: Qaz
বাংলা: গ্যাস
Bân-lâm-gú: Khì-thé
башҡортса: Газ
беларуская: Газ
беларуская (тарашкевіца)‎: Газ
भोजपुरी: गैस
български: Газ
bosanski: Plin
brezhoneg: Gaz
буряад: Хии
català: Gas
čeština: Plyn
chiShona: Gasi
Cymraeg: Nwy
dansk: Gas
Deutsch: Gas
eesti: Gaas
Ελληνικά: Αέριο
English: Gas
эрзянь: Лекся
español: Gas
Esperanto: Gaso
euskara: Gas
فارسی: گاز
Fiji Hindi: Gas
français: Gaz
Gaeilge: Gás
Gaelg: Gas
Gàidhlig: Gas
galego: Gas
ગુજરાતી: વાયુ
客家語/Hak-kâ-ngî: Hi-thí
한국어: 기체
հայերեն: Գազ
हिन्दी: गैस
hrvatski: Plin
Ido: Gaso
Bahasa Indonesia: Gas
interlingua: Gas
íslenska: Gas
italiano: Gas
עברית: גז
Basa Jawa: Gas
ಕನ್ನಡ: ಅನಿಲ
ქართული: აირი
қазақша: Газ
Kiswahili: Gesi
Kreyòl ayisyen: Gaz
kurdî: Gaz
Кыргызча: Газ
Latina: Gas
latviešu: Gāze
lietuvių: Dujos
Limburgs: Gaas
la .lojban.: gapci
magyar: Gáz
македонски: Гас
മലയാളം: വാതകം
मराठी: वायू
მარგალური: აირი
مصرى: غاز
Bahasa Melayu: Gas
Mìng-dĕ̤ng-ngṳ̄: Ké-tā̤
монгол: Хий
မြန်မာဘာသာ: အငွေ့
Nāhuatl: Ahuiyapopotl
नेपाली: ग्यास
नेपाल भाषा: वायु
日本語: 気体
Napulitano: Ggas
Nordfriisk: Gas
norsk: Gass
norsk nynorsk: Gass
Novial: Gase
occitan: Gas
Oromoo: Gaazii
oʻzbekcha/ўзбекча: Gazlar
ਪੰਜਾਬੀ: ਫੂ
پنجابی: گیس
Patois: Gias
Plattdüütsch: Gas
polski: Gaz
português: Gás
română: Gaz
Romani: Zaro
Runa Simi: Wapsi
русский: Газ
саха тыла: Гаас
Scots: Gas
shqip: Gazi
sicilianu: Gas
සිංහල: වායු
سنڌي: گيس
slovenčina: Plyn
slovenščina: Plin
ślůnski: Goz
Soomaaliga: Hawo
کوردی: گاز
српски / srpski: Гас
srpskohrvatski / српскохрватски: Gas
Basa Sunda: Gas
suomi: Kaasu
svenska: Gas
Tagalog: Gas
தமிழ்: வளிமம்
татарча/tatarça: Gaz
ไทย: แก๊ส
тоҷикӣ: Газ
Türkçe: Gaz
тыва дыл: Хей
українська: Газ
اردو: گیس
vèneto: Gas
vepsän kel’: Gaz
Tiếng Việt: Chất khí
walon: Gåz
文言: 氣體
West-Vlams: Goaze
Winaray: Gas
吴语: 气体
ייִדיש: גאז
Yorùbá: Ẹ̀fúùfù
粵語: 氣體
žemaitėška: Dojės
中文: 气体