This is a simple equation expressing the relationship between temperature and pressure. This is also related to Amontons' Law of of Pressure-Temperature. The law simple states that as temperature increases so does pressure as long as the quantities for volume and mass are constant.
Since Thermodynamics, is concerned with heat and its relation to energy and work, relating such attributes of gases as temperature, internal energy, entropy, and pressure, this law applies to both Thermodynamics and Chemistry.
The Gay-Lussac Law applies to Thermodynamics as well as a number of topics in science and engineering, in physics, chemistry, chemical engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, and materials sciences.