Any gas can be described with the Ideal Gas Law equation, #PV = nRT#, with #P# representing pressure, #V# representing volume, #n# representing the number of gaseous moles, #R# representing the ideal gas constant, and #T# representing temperature.
Since #P# is on the same side of the equation as #V#, the two variables are inversely related, and pressure will decrease as volume increases and vice versa.
Since #P# is on the opposite side of the equation as #n# and #T#, it is directly related to those variables, and pressure will increase as either the number of gaseous moles or temperature increases and decrease as those variables decrease.
(Note that #R# is a constant and cannot change)
