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Transporting gases is a difficult task. Transferring them from one location to another is nearly impossible due to the physical properties of these materials. The transformation of a gas into a liquid serves the same purpose as before. We can learn about changes in the properties and structure of a gas by studying the process known as liquefaction. Aside from that, it provides valuable information about the general structure of matter. Let’s take a look at how.
Liquefaction
It is the transformation of a gaseous substance into a liquid state that is known as liquefaction. This change is the result of a change in physical conditions such as temperature, pressure, and volume being experienced. Thomas Andrew was the first person to investigate the transition of Carbon Dioxide from its gaseous state to its liquid state. Following this discovery, it was discovered that most real gases behave similarly to Carbon Dioxide (CO2) and can transition from a gaseous state to a liquid state under the right conditions of temperature and pressure.
Andrews came to the conclusion that CO2 cannot be liquefied at high temperatures, despite the presence of high pressure, as a result of his experiment with the gas. Aside from that, the gases exhibit significant deviation from their ideal behaviour as the temperature rises as well. Carbon dioxide began to change from a gas to a liquid at 30.98° C in the case of carbon dioxide.
Critical Temperature, Volume, and Pressure
According to Andrews’ findings in his experiment, the gas sample could not be liquefied once it reached a specific temperature, no matter how high the pressure was applied. The critical temperature is the temperature at which a gas transitions from a state of being to becoming a liquid. The pressure required to liquefy a gas rises in direct proportion to the temperature of the gas under consideration. This temperature was the highest temperature at which a gas appears in the form of a liquid, according to the scientific literature. It is referred to as the critical temperature (TC).
The critical constants play an important role in the transition between different states of matter. Critical pressure, temperature, and volume are all examples of critical constants. The critical volume (Vc) of a gas volume liquefied at critical temperature is defined as the volume of one mole of the gas volume liquefied at critical temperature, whereas the pressure required to liquefy the gas at critical temperature is defined as the Critical pressure (pc).
Isotherm of Carbon Dioxide
The isotherm is a graph that depicts the relationship between pressure and volume at a constant temperature. When we look at the carbon dioxide isotherm, we can learn about the different temperature intervals at which a gas can show signs of liquefaction:
The changes in volume and pressure are critical in the transition from one state to another. The liquefaction of carbon dioxide is investigated in the isotherm.
We can see that the gaseous state of carbon dioxide changes to a liquid state at a temperature of 30.98 degrees Celsius. The curve changes when the temperature is lowered, whereas it does not change when the temperature is raised. At 30.98 degrees Celsius, the gas exhibits significant deviation from the ideal gas behaviour.
The state of equilibrium
We can see that the curve at increased pressure represents the compressibility of liquid CO2, whereas the steep line represents the isotherm of the liquid, where even the slightest compression results in a sharp rise in pressure, indicating the amount of compressibility of CO2.
This demonstrates the presence of liquid CO2. In this state, the gas exists in both liquid and gaseous forms at the same time. Further compression has no effect on the pressure of the gas at this point; instead, it results in condensation of the gas in the container. When the CO2 gas reaches this point, it has completely condensed, and further compression results in a rise in pressure.
CO2 exists in both the gaseous and liquid states, while it exists in both the gaseous and liquid states. It is a critical point in the compression of the liquid CO2 because it is nearly impossible. A state of equilibrium between the two states of matter can be observed.
We also discover that the behaviour of all the gases is very similar to that of CO2, which is due to the constant temperature or isothermal compression used in the experiment. Isothermal compression is a term used to describe the similar behaviour that gases exhibit when compressed at a constant temperature.
From Gaseous to Liquid
- The critical temperature of a gas is the highest temperature at which the first occurrence of liquefaction of a gas can be observed to take place.
The critical temperature represents the strength of the force of attraction that exists between the molecules.
The higher the critical temperature, the greater the intermolecular force of attraction and, consequently, the easier it is for the gas to liquefy itself.
liquefaction requires both cooling and compression of the gaseous state.
What gases, specifically, require both cooling and compression in order to liquefy? The gases that show a positive deviation from the compressibility factor (Z) are permanent gases, which means that they require both cooling and compression to change their state of equilibrium.
We already know that the compressibility factor is the ratio of the original volume of a gas to the molar volume; however, if the value of Z is positive or greater than 0 then it will be necessary to use both cooling and compression to achieve the desired change in state of the gas.
Compression and cooling
When you compress a gas, you are applying increasing pressure to the molecules of the gas. It brings the molecules closer together as a result of the interaction. As soon as the molecules come into close proximity to one another, the reduced temperature causes the random movement of the molecules to be slowed significantly. Intermolecular interactions are triggered as a result of the dual action of compression and cooling. When this intermolecular interaction begins, the molecules gradually and closely move toward one another, causing a change in the state of the system.
Conclusion
Liquefying a gas refers to the process of converting a gas into a liquid. It is the transformation of a gaseous substance into a liquid state that is known as liquefaction. This change is the result of a change in physical conditions such as temperature, pressure, and volume being experienced. For example, when high pressure is applied to a gas, the gas is compressed, and when the temperature of the gas is reduced, the gas is cooled
By observing the behaviour of carbon dioxide in both the gaseous and liquid states, Thomas Andrews was able to determine the complete relationship between volume, temperature, and pressure of a substance in either state. Andrews came to the conclusion that CO2 cannot be liquefied at high temperatures, despite the presence of high pressure, as a result of his experiment with the gas. After conducting additional research into this relationship, it was discovered that the high-temperature isotherms are similar to those of an ideal gas, but that the gas cannot be liquefied even under high pressure. Carbon dioxide began to change from a gas to a liquid at 30.98° C in the case of carbon dioxide. Whenever the temperature of the gas is lowered, the curve begins to deviate from the ideal curve.
