Gay-Lussac’s Law

One of the most amazing aspects that we can know about gases is that, despite the great differences in the chemical properties that each one of them has, all gases more or less obey the gas laws . Gas laws refer to how gases behave with respect to pressure , volume , temperature, and quantity .

Gay-Lussac's LawThe Gay-Lussac Law states that when the gases react , they do volumes that have a relationship single one another, and that the volume of the formed product, if gaseous , maintains the temperature and pressure constant .

  • What is the Gay-Lussac law?
  • History
  • Who proposed it
  • Gay-Lussac Law Statement
  • Formula
  • Experiments
  • Applications
  • Importance of the Gay-Lussac law
  • Examples

What is the Gay-Lussac law?

Gay-Lussac’s law is a law that tells us that depending on the volume  that exists constantly , the pressure  of a gas will be directly proportional to the temperature . When the temperature is increased, the molecules that a gas has mobilize more quickly and for this reason the number of shocks that occurs against the walls increases, in other words, the pressure is increased since the container has fixed walls and its volume cannot change.

It consists of establishing a relationship between the pressure  and the temperature of an ideal gas, keeping it at a constant volume , by means of a constant of direct proportionality . In the we are told that when there is a constant volume, as the temperature increases , the pressure of the gas increases and when the temperature decreases , the pressure of the gas decreases.


The law was first published by Louis Joseph Gay-Lussac in 1802, but it made reference to the unpublished work of Jacques Charles , from around 1787, which led to the law being usually attributed to Charles. The relationship had been anticipated earlier in the works of Guillaume Amontons in 1702.

Who proposed it

The scientist who proposed the law was Gay-Lussac who was born in St. Leonard , a town in southern France , and who studied at the École Polytechnique in Paris . Upon leaving it, in 1801, he began his work in the Department of Roads and Bridges. He began his investigations when he was chosen by Berthollet to work as his assistant in government chemical establishments .

Gay-Lussac Law Statement

Gay-Lussac’s law states as a statement that:

“At constant volume , the pressure exerted by the gas is directly proportional to the absolute temperature it supports”


The mathematical equation or formula that explains Gay-Lussac’s law is written as follows:

1 / T 1 = P 2 / T 2


  • 1 =  Initial Pressure
  • 1 =  Initial Temperature
  • 2 =  Final Pressure
  • 2 =  Final Temperature


Some experiments that can be done with this law are:

Experiment 1


  • Test tube
  • Water
  • Cork
  • Candle


  • A little water is placed in a test tube and the tube is covered with a cork.
  • Then you begin to heat the tube with a candle, the gas that was inside the tube (the steam generated by water and air) began to expand.
  • An escape route will be needed so the cork will fly off and the gas will now be able to leave quietly.

Experiment 2


  • Glass bottle
  • Candle
  • Rubber balloon


  • At the top of the bottle we will put the mouth of the balloon and then we will heat the bottle.
  • After a long time, the gas will be released until the rubber balloon is inflated.


Some of the applications in which we can observe this law are the following:

  • Gay-Lussac’s law is applied in our daily life, for example in pressure cookers in which when the temperature of the pot is increased , the gas inside will raise its pressure .
  • To design propellants in cans the pressure so that gas can build up and then have a controlled outlet .
  • In soda or soft drink cans they are known as popular, use of gases is made , since the amount of gas that is dissolved in a liquid is directly proportional to the pressure that gas exerts on the liquid. Since soda is a liquid that uses carbon dioxide , when the can is opened the gas escapes and the dissolved carbon rises to the top and escapes, hence the sound it emits.

Importance of the Gay-Lussac law

Basically, the importance of this gas law is that it tells us that as the temperature of a gas increases, its pressure increases proportionally, assuming that the volume does not change. In much the same way, when the temperature is lowered, the pressure drops proportionally.


In everyday life the Gay-Lussac law has a wide range of applications and some of the most common examples are mentioned below:

  • When a car tire is on fire : the burning rubber will cause an increase in air pressure in the tire because there is an increase in temperature which can cause an explosion of the tire wall.
  • When a bullet is fired : Gay-Lussac’s law can be applied in this case when the ignition of the gunpowder forms a superheated gas that at the same time increases the pressure causing the bullet to travel at high speed for much longer.
  • When a closed aerosol can is heated : the increase in temperature increases the pressure that could cause the container to explode. This is why we see a warning on deodorant bottles and other canned goods.
  • Heating food in an oven : By placing food in an oven to heat it, the air inside the oven heats up and becomes pressurized.

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