# How can we use bulk-phase thermodynamics when gravity disrupts a phase's uniformity?

I am starting a course in thermodynamics, and two assumptions that the instructor listed for equations of state to apply is that:

1. the system is invariant with time; and

2. that the bulk physical properties are uniform.

However, if we consider a cylinder of ideal gas, the pressure is not uniform, is it? I was taught that pressure in a cylinder of ideal gas would be greater at the bottom of the cylinder, just like how atmospheric pressure is higher at lower altitudes.

Question: How can bulk-phase physical descriptions, e.g. $$PV = nRT \tag{ideal gas law} \,,$$ be applied when a bulk-phase isn't actually uniform due to phenomena like gravity?