Ideal Gas Equation and Absolute Temperature – Class 11 | Chapter – 11 | Physics Short Notes Series PDF for NEET & JEE

Ideal Gas Equation and Absolute Temperature: The ideal gas equation, also known as the equation of state of an ideal gas, is a fundamental relationship between the pressure, volume, temperature, and the number of moles of a gas. The equation is given by:

PV = nRT


  • P is the pressure of the gas (in pascals or atmospheres)
  • V is the volume of the gas (in cubic meters or liters)
  • n is the number of moles of the gas
  • R is the universal gas constant (8.314 J/(mol.K) or 0.08206 L.atm/(mol.K))
  • T is the absolute temperature of the gas (in kelvins)

The equation describes the behavior of an ideal gas, which is a theoretical gas that is composed of particles that have negligible volume and do not interact with each other except through perfectly elastic collisions. Although no real gas perfectly follows this model, many gases behave closely to the ideal gas law under certain conditions, and the equation is useful for predicting the behavior of gases in a wide range of situations.

Ideal Gas Equation and Absolute Temperature

Absolute temperature is a thermodynamic temperature scale that is based on the properties of an ideal gas at a constant pressure. The most commonly used absolute temperature scale is the Kelvin scale, which is defined by setting the zero point at absolute zero, the theoretical temperature at which all matter would have zero entropy.

On the Kelvin scale, the unit of temperature is the Kelvin (K), and the size of the degree is the same as that of the Celsius scale. One Kelvin is equal to one degree Celsius, and the relationship between the two scales is given by:

T (K) = T (°C) + 273.15

Absolute temperature is important in thermodynamics because it allows the behavior of a system to be described in terms of its absolute energy rather than its relative energy. This makes it possible to predict the behavior of a system under different conditions, and to compare the behavior of different systems.

One important consequence of absolute temperature is the second law of thermodynamics, which states that no process can result in a net transfer of heat from a colder body to a hotter body without the expenditure of energy. This principle is a fundamental constraint on the behavior of all physical systems, and it is the basis for many important applications in engineering, chemistry, and physics.

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By Team Learning Mantras