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What is Charles’ Law?

by Soft2share.com

In the field of Science, students do come across many a type of principles that are being followed. All the mechanism which actually takes place is on the basis of the application of few basic principles.

Charles’s law is being defined as a statement that the volume occupied by a fixed amount of gas will be directly proportional to its absolute temperature if the pressure remains constant. This type of relation was first suggested by the French physicist J.-A.-C. Charles in the year 1787 and then it was later placed on a sound empirical footing by the chemist Joseph-Louis Gay-Lussac. The special case of the general gas law can also be derived from the kinetic theory of gases taking the assumption of a perfect (ideal) gas. If we look at the measurements it shows that at constant pressure the thermal expansion of real gases will be at sufficiently low pressure and high temperature, which conforms closely to Charles’s law.

This law is most commonly being referred to as the law of volumes. This is one law that gives a detailed account of how gas expands when the temperature at which the gas exists is being increased. On the other hand, we can also learn that when there is a decrease in the temperature of the gas it will lead to a decrease in volume as well.

So, in a normal environment, when we compare a substance under two different conditions, and then we apply the above statement we can write the representation in the following manner:




From the above equation, what we can derive is that as the absolute temperature increases, the volume of the gas also goes up in proportion. In simple words, the Charles law is also being known as the special case of the ideal gas law. This is one law that will be applicable for the ideal gases that are held at constant pressure but the temperature and volume keep changing.

Derivation of Charles Law

First of all let we need to understand the derivation of the Charles law. We all know that at constant pressure, the volume of the fixed amount of the dry gas is directly proportional to absolute temperature. So, taking that into consideration, we will be able to derive the following representation.


Since V and T are varying directly, we will be able to equate them by making use of the constant k.

V/T=constant =k

If we look at the equation, the value of k depends will always depend on the pressure of the gas, the amount of the gas, and also on the unit of the volume that is in consideration.


For, the equation, we are considering V1 AND T1 to be the initial volume and the temperature, respectively of an ideal gas.

We can rewrite the write equation (1) as


So, in the same equation if we change the temperature of the gas to T2, alternatively, we will notice that its volume changes to V2. So, we will be able to represent that as:


 Here, we will try and equate the above equations that is equation 2 and 3, we will be able to represent as:




We are all aware that on heating up a fixed amount of gas there will be increasing the temperature the volume also increases.

You are unaware of the fact that, on heating up a fixed amount of gas, that is, by increasing the temperature the volume also increases. In a similar manner, as we will decrease the temperature, the volume of the gas will also decrease. However, as we see that at 0-degree centigrade, the volume of the also increases by 1/273 that is what is said about the original volume for a unit degree increases in temperature.

 So, we can see that the relation between temperature and the volumes for the ideal gases can always be calculated.


In many of the day-to-day life activities, we make use of this Charles law.  Say for example, in the winters, as the temperature decreases, if we take a basketball outside in the ground the ball shrinks. This makes it important that we should check the temperature outside take the car outside as the car tyre tends to sink. The same principle applies to the inflated object.

 However, on a hot day, if we overfill a tube that is placed on a pool on a hot day, we will see that the tube can swell up in the heat of the sunrays and can even burst. The same principles do follow when we cook the turkey the gas inside the thermometer expands until it can “pop” the plunger. The most common example is the way the car engine works.

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