Gas is one of the aggregate states of matter. It is widespread both on Earth and beyond. Gases can freely be in nature or released during chemical reactions. They participate in the breathing of most living things on the planet, and man has learned to use them in everyday life, industry, medicine and other fields of activity.
Gas is what?
In its state, gas is very similar to steam. It is a formless ephemeral substance that fills any space. Unlike steam, it does not transfer to liquid when its pressure increases.
Its name means “chaos” and was invented by the Dutch scientist Jan van Helmont. The gas molecules are very weakly bound, they move as they like, sometimes colliding and changing their trajectory. This state of affairs reminded Helmont of primitive chaos.
Gas is the basic state of matter in the universe. It forms nebulae, stars and atmospheres of planets. The air shell of the Earth also consists of gas, more precisely a mixture of various gases, dust, water and aerosols.
Basic properties
Most gases do not have pronounced physical characteristics. They are colorless and odorless. It is more difficult to describe the quality of a gas than any mineral that we clearly see and can touch. To characterize them, use the following parameters: temperature, volume, pressure and number of particles.
Gases do not have a specific shape and take the form of the object in which they are located. In this case, the substances do not form any surface. They always mix. The same amount of gas will fill both a small jar and a large room. But in the second case, the distance between the molecules will increase significantly, and its concentration in air will be less.
The pressure of a substance is the same at any point when gravitational forces do not act on it. With their influence, the pressure and density of gases decreases with height. It feels great in the mountains, where at high altitudes the air becomes rarefied.
With increasing temperature, the gases expand, while the velocity of the molecules increases. With increasing pressure and density, they, on the contrary, are compressed. They conduct heat and electricity poorly.
Combustion
By their ability to enter into a combustion reaction, gases can be divided into oxidizing, neutral and combustible. The least active substances are neutral or inert gases: argon, xenon, nitrogen, helium, etc. They interact worst with compounds and materials, and are also able to stop and limit combustion.
Oxidizing agents include oxygen, air, nitric oxide and dioxide, chlorine, fluorine. By their nature, they are not combustible, but they perfectly support this reaction. Under certain conditions, they can self-ignite and even explode, for example, when combined with grease or grease.
Combustible gases are ammonia, methane, carbon monoxide, propane, propylene, ethane, ethylene, hydrogen and others. In nature, they can be in a calm state. But, mixed in the right amount with oxygen or air, ignite. This does not happen if the oxidizing agent is too little or too much. So, for the complete combustion of methane gas (1 kg), about 17 kg of air is needed.
Interesting Facts
- Many gases are very light. The record holder among them is hydrogen, which is 14 times lighter than air. One of the most severe at room temperature is radon. Of the inorganic compounds, the most severe is tungsten hexafluoride.
- The most inert and inactive gas is helium. It is the second easiest after hydrogen, but it is not explosive, which is why it was used for airships.
- In outer space, the most common gas is hydrogen.
- Oxygen is the most abundant in the earth's crust, and radon is the least abundant.
- Under normal conditions, not all gases are colorless. Ozone has a blue color, chlorine is colored yellow-green, red-brown hues are characteristic of nitrogen.