Kinetic Theory Of Gases – A Model Of Gases As Moving Particles

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What Is Kinetic Theory Of Gas?

Kinetic Theory Of Gases– A Model Of Gases As Moving Particles

The Kinetic Theory Of Gas is a statistical model that precisely describes the materialistic behavior of gas. According to the Kinetic Molecular Theory Of Gas, “the submicroscopic particles (atoms or molecules) that make up the gas are constantly moving in random motion, and that randomness arises due to the collision of molecules not only with each other but also with the sides of the wall of the container”.

Any sample of gas is made up of molecules (submicroscopic particles) having all the chemical properties of the gas. The kinetic theory of gas explains macroscopic physical properties of the gas such as heat, temperature, pressure viscosity, etc by evaluating their molecular composition and motion. The kinetic theory of gages is sometimes also pronounced as a Kinetic Model or Kinetic Molecular Model etc.
The Kinetic Theory can also be applied to fluids as well and the phenomenon is known as Brownian motion explained by Albert Einstein in 1905. 

History Of Kinetic Molecular Theory

If we go deep down in the historical timeline; it was Lucretius a Roman Greek poet and philosopher who advocated The Theory Of Atomism. He proposed that all the macroscopic bodies are made up of rapidly moving very small atoms that are constantly bouncing off each other. But sadly, his theory of atomism was completely abandoned for centuries because of the dominance of Aristotlean View. 
So many centuries after Lucretius’s hypothesis, in the year 1738 Daniel Bernoulli a Swiss Mathematician and Physicist devised his Kinetic Theory Of Gases. Bernoulli’s arguments were the same as Lucretius’s that we are using until today. His theory didn’t influence the physicist of that time because the Law Of Conservation Of Energy had not been established at that time; so as a result physicists were unable to understand that how the collisions between molecules could be perfectly elastic.

Within one century, physicists around the globe started to recognize the kinetic theory of gases i.e modern view of matter as composed of small particles called atoms and molecules.  In the year  1857, a German Chemist and Physicist August Krönig proposed his Kinetic-Gas Model, in which he explain the translational motion of particles; which was later modified by Rudolf Clausius a German-born Physicist and Mathematician who not only explained the translational motion of particles but also explained the rotational and vibrational motion of particles. In the year 1859, after examining the work of Clausius; a Scottish Scientist and Mathematical Physicist James Clerk Maxwell formulated his world-famous Maxwell Distribution of molecular velocities (This was the first-ever statistical law in physics) which was later generalized by Ludwig Boltzmann an Austrian physicist and philosopher into Maxwell-Boltzmann Distribution.

Even after so many happenings, the 20th-century physicist believed that atoms are rather purely hypothetical construct; i.e atoms are not real. This dilemma that whether atoms are real or just a hypothetical construct was finally resolved by Albert Einstein in his 1905 papers. Einstein developed a diffusion formula by applying the statistical method and later that phenomenon to be known as Brownian motion.

Editor’s Choice: Dalton’s Law – The Law of Partial Pressure

Assumptions Of The Kinetic Theory

The Kinetic-Molecular Theory of ideal gases are as follow:
  1. All gases are made of molecules moving randomly in all possible directions.
  2. The size of a molecule is much smaller than the average separation between molecules.
  3. The molecules exert a force on each other and the wall of the container only at the time of the collision.
  4. The collision between particles and the wall of the container is perfectly elastic.
  5. The molecules obey Newton’s laws of motion.
  6. When the gas is left unhindered for sufficient time, it comes to the steady-state.
  7. Each molecule is treated identically to the other molecules and their results are obtained on average using the statistical method.

The Ideal Gas Law

The Ideal Gas Law or sometimes called the General Gas Equation; is the equation of state for describing the behavior of many gases under different conditions. This equation was first derived by a French Engineer and Physicist Benoît Paul Émile Clapeyron in1834 by combining Boyle’s Law, Gay-Lussac’s law, Avogadro’s Law, and Charles’s Law. Mathematically it is described as:
P = pressure of the gas
V = volume of the gas
n = amount of substance taken (in moles)
R = ideal or universal gas constant ( product of Boltzmann constant and Avogadro constant)
T = absolute temperature of the gas

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I am a Physics Educator, positively impacting the students by igniting their imagination and curiosity about nature as well as their laws and guiding them to answers. Talking about education, I am a postgraduate in physics and trying to collect as much as I can out of the immense treasure of knowledge.

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