Born 240 years ago in Paris, Gay-Lussac is most notably acknowledged for his definition of the ‘ideal gas law’ that looks at the thermal expansion of gasses.

Gay-Lussac studied at École Polytechnique in Paris, and then went on to work with notable scientists such as Claude-Louis Berthollet, Louis-Jacques Thenard and Jean-Baptiste Biot.

The Ideal Gas Law

Also known as the Pressure Law, this defines the relationship between the pressure and temperature of a fixed mass of gas kept at a constant volume.

• If a gases temperature increases, so does the pressure if the mass and volume of the gas are held constant
• The formula for the law is most commonly stated as: PV=nRT
• P is the pressure of the gas,
• V is the volume of the gas,
• n is the amount of substance of gas (also known as number of moles),
• R is the ideal, or universal, gas constant, equal to the product of the Boltzmann constant and the Avogadro constant,
• T is the absolute temperature of the gas.

where:

A computer animated version of the law is illustrated on the NASA website here.

Giving Credit to Charles

A previous scientist, Jacques Charles, provided the foundations for Gay-Lussac Law by defining the law of volumes, explaining that gas expands when heated. It was Gay-Lussac that further confirmed this.

Practical Applications Using Gay-Lussac’s Law

• Demonstrate the relationship between pressure and temperatures of a fixed volume of an ideal gas with the Ideal Gases – Gay-Lussac’s Law Experiment (TD1001).

Further Experiments for Learning the Gas Laws

• Understand Boyle’s Law of Ideal Gasses (TD1000) that shows the relationship between pressure and volume of an ideal gas at a fixed temperature.
• Demonstrate the behaviour and expansion of a perfect gas with the Expansion of a Perfect Gas experiment (TD1004).