Table of contents


Gas Laws

Science is all about making observations and exploring new things. For this purpose, many scientists struggled in the past two centuries to discover new phenomena.

Through their continual efforts, we became able to learn the science and logic behind almost all the natural events today.

Since matter - any entity that occupies space and possesses some mass- is the basic entity known to scientists, and all the research revolves around it. As we all know, there are four basic states of matter; Solid, Liquid, Gas, and Plasma.

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Among all these states, the state possesses completely different features from other states is gas. That's why several scientists spent so much time studying the behavior of gases by various methods in their periods.

These observations, when tested, again and again, earned the status of laws that we know today as GAS LAWS IN CHEMISTRY. These laws describe the behavior of gases in different conditions of temperature, pressure, and volume.

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What are the five gas laws?

Five main gas laws in chemistry are considered completely authentic and describe the major behavior of gases in varied environments. These five gas laws are as follows.

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  1. Boyle's Law

    Boyle's law is named after the scientist Robert Boyle. This law shows the relationship between pressure and volume of a gas when the temperature is kept constant. According to it, the pressure of a gas is inversely proportional to its volume at a constant temperature.

    In simple words, whenever the pressure over gas is increased, its molecules get closer to each other on compressing. Thus, its volume decreases.

    However, this condition can only be achieved when the temperature is kept constant. Otherwise, the effect of the varying temperature might change the behavior. Boyle's law can be written mathematically, such as

    Pressure ∝ 1/volume

    T = Constant

    P ∝ 1/V

    To replace the proportionality constant, we will replace the 1 with K, such as

    P ∝ K/V

    On rearranging the equation, it would become

    PV = K
  2. Charles Law

    Charles law is named after the scientist J. A. C. Charles, and it shows the relationship between temperature and volume of a gas when the pressure is kept constant. According to it, the temperature of a gas is directly proportional to its volume at constant pressure.

    In simple words, as the temperature of a gas is increased, the molecules of gas get enough kinetic energy to free up from intermolecular forces. Resultantly, the gas molecules will become more distant from each other, and thus, the volume of that gas will increase.

    Again, the pressure should be kept constant to observe this behavior. Mathematically, we can write Charles law as follow

    V ∝ T

    P = Constant

    To remove the proportionality sign, we will add proportionality constant in the equation, such as

    V = KT

    On rearranging the equation, it would become

    V/T = K
  3. Gay Lussac's Law

    Gay lussac's law is named after French scientist Joseph Louis Gay Lussac. The interesting thing about this law is that he accidentally discovered it when he was busy making an air thermometer.

    This law explains the relationship between pressure and temperature of a gas at a fixed volume. According to it, gas pressure is directly proportional to its temperature when the volume is kept constant. Mathematically, we can write Gay lussac's law such as

    P ∝ T

    V = Constant

    P = KT

    P/T = K

  4. Avogadro's Law

    Amedeo Avogadro studied the relationship between the volume and number of moles of gas by keeping the observations of Gay Lussac's law and John Dalton in front.

    According to avogadro's law, all gases possess an equal number of molecules and, thus, the same volume at constant temperature and pressure.

    In other words, the volume of a gas is directly proportional to its number of molecules at constant temperature and pressure. Mathematically, avogadro's law can be written as

    V ∝ n

    V = Kn

  5. Ideal Gas Law

    Ideal gas law combined all the four gas laws and was first proposed by Benoît Paul Émile Clapeyron. It shows the behavior of ideal gases. Plus, by using this law, we can also approximate the nature of real gases.

    On combining mathematical forms of the first four laws, we get the equation-of-state such as

    PV = nRT

    In this combined gas law equation, n is the number of moles, and R is the general or universal gas constant.

Final Words

All these gas laws show how gases perform in different environments. These laws might seem a bit confusing, but they possess great importance in our daily lives.

By these gas laws, we get a perfect illustration of how our breathing pattern, movement of vehicles, and even the natural events could alter on experiencing slight changes in temperature and pressure.

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