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Liquification of Gases

Last Updated : 10 May, 2022
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Matter is defined as anything that occupies space and has mass. Modern scientists divide matter into two categories: physical properties and chemical properties. The matter is classified as solids, liquids, or gases based on its physical properties. Solids include things like sugar, sand, iron, and rocks. Water, milk, petrol, oil, among others, are liquids, while air, oxygen, and steam are gases. By altering pressure and temperature, one state of matter can be transformed into another. Applying pressure and lowering the temperature can turn a gas into a liquid. This is covered in depth further below.

What are Gases?

All matter can be categorized into three types based on their physical states: solids, liquids, and gases. Common gases include air, oxygen, hydrogen, nitrogen, carbon dioxide, and others. When compared to solids and liquids, the distance between particles in gases is substantially greater. 

A gas has relatively big gaps between its particles. The attraction between the particles in a gas is extremely weak. As a result, gas particles are free to flow in any direction. The positions of gas particles, as well as the distances between them, are not fixed. 

A gas’s particles have the highest kinetic energy. As a result, gases have the most disorganized particle arrangement. The particles of a gas move at great speeds in all directions due to tremendous kinetic energy and low forces of attraction. When fast-moving gas particles collide with the container’s walls, gas pressure is exerted by the particles. As a result, a gas exerts pressure on the container’s walls. When a gas is put into an empty container, it spreads swiftly across the container and entirely fills it. When a gas is heated, the gas’s particles begin to move quicker and faster.

Some of the characteristics of gases are.

  1. The shape of the gas is not fixed.
  2. There is no such thing as a fixed volume for a gas.
  3. Since its particles are widely apart and there are large gaps between them, a gas can be compressed easily.
  4. Since the particles in a gas are so far apart, it has an extremely low density.
  5. A gas fills its containers fully because its particles are travelling at rapid speeds in all directions due to high kinetic energy and low forces of attraction.
  6. A gas flows freely because its particles are unrestricted in its movement.

Changing the pressure can also modify the physical condition of matter. To put it another way, the physical condition of matter can be altered by increasing or lowering pressure. Gases, for example, can be converted to liquids by increasing pressure while lowering the temperature. When the pressure is reduced, some solids, such as solid carbon dioxide, can transform into gases.

Liquification of Gases – By applying pressure and lowering temperature

The process of liquefaction of gases is the transformation of substances from their gaseous state to their liquid state. Gases are a type of substance in which particles are often very far apart, move very quickly, and do not have strong attraction forces between them. Within the particles, there is a lot of empty space, and these particles have a lot of kinetic energy. Particles in liquids, on the other hand, are confined by fairly strong forces of attraction, and their kinetic energy is lower than that of gaseous particles.

A gas is compressed into a tiny volume when high pressure is applied to it, and it is liquefied when the temperature is lowered. As a result, we may argue that gases can be liquefied and converted into liquids through compression and cooling. This occurs in the following manner.

Gas turning into liquid

  • A gas has a lot of space between its particles. By confining a gas in a cylinder and compressing it with a piston, we can minimize the space or distance between its particles. 
  • The gas is highly compressed into a small volume if enough force or pressure is applied to the piston. The gas particles become so close together that they begin to attract each other enough to form a liquid, and the gas is said to have liquefied. When a gas is compressed excessively, heat is created as a result of the compression
  • As a result, it is required to cool gases while applying pressure to liquefy them in order to remove the heat generated during compression. Cooling helps to liquefy compressed gas by lowering its temperature. As a result, it may be deduced that applying pressure and lowering the temperature can liquefy gases. 
  • To put it another way, gases can be liquefied through compression and cooling. Before liquefication by pressure may occur, the gas must be cooled below a particular temperature. 
  • Water is routinely poured over the coils that convey the compressed gas to keep them cool. By applying high pressure and lowering the temperature, ammonia gas can be liquefied. That is, compressed and cooled ammonia gas can be liquefied. As a result, changing the state of matter from a gas to a liquid can be accomplished by increasing pressure and decreasing temperature.
  • As a result, increasing pressure and lowering temperature can liquefy gases. When pressure is applied to the gaseous particles, they cluster together and begin to attract one another. 
  • When a gas’s pressure is increased, its molecules become closer together, and its temperature drops, removing enough energy to cause it to transition from a gaseous to a liquid state. When the gas is exposed to high pressures and low temperatures, it can liquefy. The pressure and temperature that must be applied are determined by the molecular forces of the gas molecules. 

Solid being converted into Gas

  • Changing the state of matter from a gas to a liquid can be accomplished by increasing pressure and reducing temperature. Even changing the state of matter by lowering the pressure and rising the temperature is possible. Take, for example, the storage of solid carbon dioxide or dry ice under high pressure. 
  • This is due to the fact that when the pressure on solid carbon dioxide is reduced, it is instantly transformed into carbon dioxide gas. When a slab of solid carbon dioxide is exposed to air, the pressure on it is decreased to normal atmospheric pressure, the temperature rises, and the carbon dioxide gas begins to form. 
  • As a result, the transformation of solid carbon dioxide into carbon dioxide gas is a shift in the state from solid to gas, which is initiated by a drop in air pressure and a rise in atmospheric temperature. Solid carbon dioxide is a type of dry ice that is white in colour. Carbon dioxide in solid form is a very chilly substance. It’s used to keep ice cream cool and to deep freeze meals. Dry ice is defined as solid carbon dioxide that converts directly to carbon dioxide gas rather than melting to generate liquid-like ordinary ice.

Sample Questions

Question 1: Why don’t gases have a fixed shape and volume?


Since the positions of its particles are not fixed, gases do not have a fixed shape, and gases do not have a fixed volume because the spaces between its particles are not fixed.

Question 2: When a gas is heated, what happens?


When a gas is heated, the gas particles begin to move more quickly.

Question 3: Why do gases exert pressure on the container’s walls?


The pressure exerted by a gas is caused by collisions of fast-moving gas particles with the container’s walls.

Question 4: Why is dry ice so much more efficient at cooling than regular ice?


Dry ice can produce temperatures that are substantially lower than ordinary ice. As a result, it is far more effective at cooling than ordinary ice.

Question 5: In a liquid state and a gaseous state, how are the particles arranged?


In the liquid state, particle arrangement is less organised, and in the gaseous state, particle arrangement is non-existent.

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