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Difference between Ideal Gas and Real Gas

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Introduction:What is Ideal Gas and Real Gas?

Gases are an essential part of our everyday lives, from the engines that drive our cars to the cooling systems in our houses. The ideal gas and actual gas are the two essential ideas. These ideas offer insightful information on the traits and features of various gases. Let's think about an everyday situation: blowing up a balloon, to better understand the distinction between ideal gas and real gas.

Have you ever pondered the mechanism behind a balloon's expansion after receiving air? An interesting look into the universe of gases and the distinction between ideal gas and real gas can be gained through the operation of inflating a balloon. This article will examine the distinctions between ideal and actual gases as well as their definitions, characteristics, and uses.

Ideal Gas:

An ideal gas is a hypothetical conception that symbolises a gas that complies with specific presumptions and abides by the ideal gas rule. It is predicated on the idea that the gas particles have a tiny volume and do not interact with one another intermolecularly. In other words, an ideal gas presupposes that everything is flawless and that there are no interactions between the gas particles.

The behavior of an ideal gas is described by the ideal gas law, which relates the pressure (P), volume (V), and absolute temperature (T) of the gas. The ideal gas law equation is given as PV = nRT, where n represents the number of moles of the gas and R is the universal gas constant.

In this equation, R is a constant that is equal to 8.3145 J/(mol K) or 0.0821 L/atm/(mol K) depending on the units used. Given the values of the other variables, the ideal gas law is used to compute the volume, pressure, and temperature of an ideal gas, among other features.

Real Gas:

Real gas, in contrast to an ideal gas, exhibits properties that deviate from the assumptions of the ideal gas law. Real gases have non-negligible intermolecular forces of attraction and occupy a definite volume. Unlike the hypothetical nature of ideal gases, real gases exist in the physical world and can be found in various environments. The behavior of real gases is influenced by factors such as temperature, pressure, and molecular interactions. At high pressures and low temperatures, real gases tend to deviate significantly from ideal gas behavior. The intermolecular forces between the gas particles become more pronounced, resulting in a reduction in volume and increased molecular interactions.

One important characteristic of real gases is their tendency to liquefy when cooled to sufficiently low temperatures or high pressures. This occurs due to the increased intermolecular forces causing the gas particles to come closer together and form a liquid phase.

Difference between Ideal and Real Gas:

The difference between ideal gas and real gas can be understood by examining the assumptions made about their behavior. Ideal gases are a theoretical concept used to simplify calculations and describe gases under idealized conditions. They serve as a model that assumes certain characteristics of gas particles to make calculations more manageable. On the other hand, real gases take into account the complexities of intermolecular forces and molecular interactions that exist in the physical world.

The table describes the comparison between Ideal and Real gas:

Ideal Gas

Real Gas

Ideal gases are assumed to have negligible or no intermolecular forces of attraction between the gas particles.

Real gases experience intermolecular forces of attraction between the gas particles, which can be significant under certain conditions.

Ideal gases are thought to have no intrinsic volume. They are taken to fill the full space and have an endless capacity for expansion and contraction.

Real gases take up space and have a known volume. It is impossible to ignore the size of the individual gas particles.

A perfect gas's particles collide elastically, which means there is no kinetic energy lost during contact.

A real gas's particle collisions could not always be fully elastic, which might cause kinetic energy to be lost or transferred.

Ideal gases are considered to have no defined mass.

Individual gas particles contribute to the overall mass of real gases, which have a fixed mass.

Ideal gases follow the ideal gas laws, such as Boyle's law, Charles's law, and Avogadro's law, which describe their behavior under specific conditions.

At high pressures and low temperatures, real gases depart from the rules of ideal gases. 

Ideal gases are hypothetical and do not exist in their pure form in the real world.

Real gases exist in the physical world and can be found in various environments. Examples of real gases include carbon dioxide, nitrogen, oxygen, and water vapour.


We have looked at what is ideal gas and real gas, and the key distinctions between them. A perfect gas has no internal volume and is characterised by the absence of intermolecular forces of attraction. It is presumed that an ideal gas's particles are fully elastic and freely moving. However, a real gas deviates from the behaviour of an ideal gas because it has mass and volume as well as intermolecular forces of attraction.

The classifications of real gas and ideal gas draw attention to the differences in their characteristics and behaviours. A real gas does not precisely obey the gas laws and necessitates more complicated equations to fully explain its behaviour, whereas an ideal gas adheres to the Ideal Gas Law and is frequently employed in theoretical calculations.

For several applications in physics, chemistry, and engineering, it is essential to comprehend the differences between these two categories of gases. In real-world situations, when intermolecular forces and molecular interactions are at play, real gases play a crucial role. Real-world gases behave differently at different pressures, temperatures, and volumes, and this has effects on areas like thermodynamics, gas dynamics, and chemical reactions.

Last updated date: 29th Sep 2023
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FAQs on Difference between Ideal Gas and Real Gas

1. Can a gas transition from being real to ideal or vice versa?

Changes in conditions cause changes in gas behaviour. Greater divergence from ideal behaviour and a movement towards real gas characteristics are caused by higher pressure or lower temperature. On the other hand, perfect gas behaviour can be achieved by increasing temperature or decreasing pressure.

2. How are ideal gas and real gas equations different?

The Ideal Gas Law and other ideal gas equations make no assumptions about intermolecular interactions or molecular volume. Real gases need complex equations that take these considerations into account, like the van der Waals equation.

3. Is ideal gas behaviour significant in real-world applications?

In thermodynamics, gas dynamics, and the development of gas-based systems like air conditioning, ideal gas behaviour is used as an approximation. Despite variations in the behaviour of real gases, it offers a starting point for computations and research.