Charles' Law and Gay-Lussac's Law each explore two and only two parameters. In both cases, all but the two parameters of interest are held constant.
- Gay-Lussac's Law explores the relationship between pressure and temperature assuming volume* and number of molecules of gas remain constant.
- Charles' Law explores the relationship between temperature and volume assuming pressure and number of molecules of gas remain constant.
In the soda can experiment, the boiling water fills the can with water vapor, driving out other gases. When the can is sealed, most of container is filled with water vapor. As it is then cooled, the water vapor condenses, drastically reducing the amount of gas particles in the can. It is the drop in the amount of gas rather than a change in temperature of a fixed volume of gas that allows the pressure difference between the inside and outside of the can to crush it.
