Behaviour and Properties of Gas

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Gas State of Matter

The enormous number of molecules in even a small amount of dilute gas results in simplification rather than compilation, as one would imagine. The explanation for this is that in most studies of gas behaviour and properties, only statistical averages are found, and statistical methods are very reliable when large numbers are involved. Only a few properties of gases, such as pressure, density, temperature, internal energy, viscosity, heat conductivity, and diffusivity, are important when compared to the number of molecules involved. (Electric and magnetic fields may be used to reveal more subtle properties, but they are of secondary importance.) 

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Is it Easy to Figure it?

The fact that these properties are not mutually exclusive is remarkable. If you know the first two, you can figure out the rest. That is to say, specifying only two properties for a given gas—usually temperature and density or temperature and pressure—fixes all the others. Thus, if the density and the temperature of CO2 are specified, the element can have only one possible pressure, one internal energy, one viscosity, and so on. These other properties must either be measured or estimated from the known properties of the molecules themselves in order to be determined. The ultimate aim of statistical mechanics and kinetic theory is to perform such calculations, and dilute gases are the case where the most progress has been achieved.

Equilibrium Properties

Ideal Gas Equation of State

Apart from its low density as compared to liquids and solids, a dilute gas's most noticeable Behaviour and properties are its high elastic behaviour of solids or compressibility and large volume expansion when heated. Both dilute gases have almost identical properties. Almost all of these gases can be correctly represented using the universal equation of state- pv=RT.

Since all real gases deviate slightly from this expression, it is referred to as the ideal, or perfect, gas equation of state. These deviations become less important as the density of the gas decreases. The pressure is p, the volume per mole is v, the universal gas constant is R, and the absolute thermodynamic temperature is T. If the volume is more than 10 times the critical volume, the expression is accurate to within a few per cent; the accuracy improves as the volume increases. In both high and low temperatures, the expression ultimately fails due to ionisation at high temperatures and condensation to a liquid or solid at low temperatures.

Internal Energy

Internal energy is a property or state function in thermodynamics that determines the energy of a material in the absence of capillary effects and external magnetic, electric, and other fields. The value of the energy, like any other state function, is determined by the state of the material rather than the existence of the processes that led to that state. The work is proportional to the change in internal energy when a system changes state as a result of a phase in which only work is involved, according to the first law of thermodynamics. If both heat and function are involved in a system's change of state, the change in internal energy is equal to the heat supplied to the system minus the work performed by the system, according to the rule.

Transport Properties

The three major transport Behaviour and properties, viscosity, heat conductivity, and diffusivity, are summarised below. The transfer of momentum, energy, and the matter is represented by these properties.


Viscosity is a form of internal friction found in all ordinary fluids. A constant force is required to keep a fluid flowing, just as a constant force is required to keep a solid body moving in the face of friction, also known as the viscoelastic behaviour of polymers. 

Heat Conduction

A flow of energy through a fluid may occur if a temperature differential is preserved through the fluid. According to Fourier's law, the energy flow is proportional to the temperature differential, with the heat conductivity or thermal conductivity of the fluid, aka, λ. Energy may be transported by mechanisms other than conduction, such as convection and radiation; it is thought that these can be omitted or modified in this case.


Diffusion is a mass transfer phenomenon that causes a species' chemical behaviour distribution in space to become more uniform over time. A chemical dissolved in a liquid or a part of a gas mixture, such as oxygen in air, is referred to as a species in this case.

Fun Fact

What is the composition of matter? Atoms are the building blocks of all matter. Atoms are the tiniest particles in the universe. They're so tiny that they can't be seen with the naked eye or even a normal microscope. A million atoms make up a typical sheet of paper. A scanning tunnelling microscope (STM), which uses electricity to map atoms, has been developed by science to classify atoms. More on atoms will be discussed later, but first, let's review the three states of matter.

FAQs (Frequently Asked Questions)

1. What is the Viscoelastic Behaviour of Polymers?

Ans: Creep under constant load, time-dependent recovery of deformation followed by load elimination, stress relaxation under constant deformation, and time-dependent creep rupture are all examples of viscoelastic or viscoplastic action of a material. The length and rate of loading have a significant impact on the deformation of polymeric materials. As the temperature exceeds Tg, it becomes more critical. Ahci and Talreja investigated creep-recovery test results for graphite fibre fabric composites with polyimide thermosetting resins with Tg values greater than 700°F. As the temperature reached the Tg value, the composite began to creep in the fibre direction. Beyond threshold stress of 13 ksi at 700°F, the viscoelastic behaviour displayed a nonlinear response.

2. What is the Rheological Behaviour of Fluids?

Ans: For today's formulators, emulsion rheological activity is becoming increasingly critical in optimising final product output and sensory attributes. The rheological behaviour of an emulsion can be influenced by the emulsifying mechanism. The experiments were carried out on an RM1-based emulsion with a 15 percent isopropyl palmitate oil process. Experiments were carried out using normal techniques on a Weisenberg rheometer with a measuring geometry of coaxial cylinders at 22°C-25°C. The structure created by an emulsion's ingredients has been attributed to its non-Newtonian (viscoelastic) rheological behaviour. In an oil-in-water emulsion based on sodium stearyl phthalate, the formation of lamellar gel network structures results in an extremely favourable rheological profile.

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