Behaviour of Gases

One may assume that the vast number of molecules in even a tiny volume of dilute gas results in simplification rather than a complication. This is because most gas behaviour and properties study only record statistical averages, and statistical procedures are rather precise when huge numbers are involved. Only a few parameters of gases, such as pressure, density, temperature, internal energy, viscosity, heat conductivity, and diffusivity, are essential compared to the number of molecules involved. While electric and magnetic fields can be used to reveal more subtle features, they are of secondary importance.

These other qualities must either be measured or derived from the known properties of the molecules themselves. The ultimate goal of statistical mechanics and kinetic theory is to perform such calculations, and dilute gases are the area where most progress has been made.

Solid, liquid, gas, plasma, and the Bose-Einstein condensate are the five primary states of matter. A unique state emerges from these gases. Their properties are simple to investigate. Thus, gases follow a set of rules known as gas laws. The behaviour of gases is described by these rules or values and relationships of temperature, pressure, and volume. The behaviour of gas molecules is dictated by the qualities and laws that the molecules in the gas follow. According to physicists, the molecular distribution of a gas, liquid, or solid has significant distinctions. Gas laws and gas properties have been created to explain the propensity and distribution of molecules in a gas. The kinetic theory of gas molecules explains the behaviour of gas molecules. Gas molecules can be studied at a microscopic level. The fact that these traits are not mutually exclusive is surprising. If you know the first two, you can figure out the remainder. In other words, specifying only two parameters for a given gas—usually temperature and density or temperature and pressure—fixes all others. As a result, if the temperature and density of carbon dioxide are known, the gas can only have one pressure, internal energy, viscosity, etc.

Properties of Gases

There are various properties of gases that you should know about when you study them. As we all know, gases do not have a definite shape, size, or weight. It is highly flexible and fills any given space. They can occupy a space completely that is given to them. For instance, oxygen. The intermolecular forces of attraction present in gases are particularly lower than that of solids and liquids. This gives all the gases adequate mobility to move around without any hindrances. Therefore, gases also have high kinetic energy and velocity. 

The main properties of gases are mentioned below:

1. Compressibility

Huge intermolecular gaps exist in the middle of gas particles. This gap can be considerably reduced by applying pressure, bringing the particles closer. As a result, the volume of gas can be drastically reduced. This is known as compressing the gas.

2. Expansibility

When you apply pressure to gas, it contracts. When the pressure is released, however, the gas expands. The constituent particles gather more energy, travel quicker, and move farther from each other as the temperature rises, resulting in less intermolecular attraction. The volume of the gas expands.

3. Diffusibility

When two gases are combined, particles from one gas flow across the intermolecular gap of the other gas with ease. As a result, both gases are thoroughly and consistently combined, and the gas mixture always remains homogeneous.

4. Low Density

Because gases have huge intermolecular gaps, their volume is significant compared to their mass. As a result, their densities are lower. If 1 millilitre of water at 39.2°F is converted to steam at 212°F at 1-atmosphere pressure, it will occupy 1700 ml of space.

5. Exertion of Pressure

Solids exert pressure solely in one direction: downward. Liquids exert pressure downward and to the sides.

Boltzmann Constant

The Boltzmann constant was named after a renowned scientist and scholar named after Ludwin Boltzmann. The Boltzmann constant is usually represented by K. Plank introduced it in the world of Physics. It is an important term of Thermodynamics. 

Boltzmann constant refers to the ratio of the Avogadro number and the ideal gas constant. To obtain the formula for the Boltzmann constant, we need to divide the Avogadro number with the ideal gas constant.

Boltzmann constant (K) = 1.3806452 × 10-23 J/K

The Boltzmann constant finds numerous applications in Physics. It helps in understanding the values of the thermal voltage in semiconductors. It also expresses the equipartition of the atom energy. 

Perfect Gas Equation

Perfect gas, also called ideal gas, conforms in physical behaviour to a specific, idealised relation between pressure, volume, and temperature called the final gas law. The perfect gas equation is governed by a law that is an amalgamation of both Charles’ Law and Boyle’s Law. It states that: 

PV = nRT

Herein, P is the pressure, and V is the volume

Further, T is the temperature given to the gases, and R is the constant here. This is the perfect gas equation. 

No gas in the universe has the attributes of a perfect gas. An ideal gas law describes the relationship between the pressure exerted by a gas, the amount of gaseous substance present, the absolute temperature of the gas, and the volume occupied by the gas. A perfect gas or general gas law is a gas that perfectly obeys the law of ideal gas. It is represented by the perfect gas equation. 

Conclusion 

We infer that particle randomness, or entropy (H), is proportional to the temperature of the molecules within the gas, so that the higher the temperature, the higher the entropy. The order of unpredictability (Entropy) in the three states of matter will be:

Solid > Liquid > Gaseous

The gaseous state has the most entropy among the three states of matter.