It’s a simple fact of physics that hot air rises and cool air sinks.
Heating and A/Cs take this into account.
For example, ductless mini-split A/Cs should be placed high up on the wall in an area of the apartment where the component will not be blocked by furniture to allow for unblocked air flow. Also, it’s good to install the outdoor components of an A/C unit on either the north or south wall of your apartment to shield it from the sun. Even having a nearby tree to offer shade can be helpful. You do not necessarily want to have debris falling from the tree onto the condenser unit. You generally also want to keep the condenser component unblocked by anything in the yard, keeping physics in mind, one of the most efficient means of heating an apartment comes in the form of radiant floors. Radiant floors consist of tubes under the flooring of your apartment that are heated either by electricity or sizzling water. Because the heat source is below the floorboards it will naturally emanate upwards, thereby efficiently heating your apartment as opposed to a forced air Heating & A/C unit with vents on the ceiling. Unless you are 8 ft tall you generally won’t like the heat hanging up there so it’s best to use radiant radiant floors, but they can be quite costly. In summary, the fact that overheated air rises and cool air descends is taken into account when it comes to the design of certain heating and A/Cs systems.