Define Gay-Lussac's Law.

Gay-Lussac's Law states that the pressure of a gas is directly proportional to its absolute temperature, when the volume is kept constant. This law is also known as the pressure-temperature law. Mathematically, it can be expressed as P1/T1 = P2/T2, where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the final pressure and temperature.

Gay-Lussac's Law states that the pressure exerted by a gas is directly proportional to its temperature in Kelvin at constant volume. Mathematically, it can be expressed as:

P = k - T

where:
- P represents the pressure of the gas
- T represents the temperature of the gas in Kelvin
- k is a constant