This question was inspired by Why does liquid water form when we exhale on a mirror?.

It is different from Why does water evaporate at room temperature? because it asks about whether an equilibrium is established. It is clear that at room temperature under certain circumstances, water molecules leave the liquid phase and end up in the gas phase.

Consider the reversible reaction between water in the liquid and in the gas phase:

$$\ce{H2O(l) <=> H2O(g)}$$

At room temperature and atmospheric pressure, for which of the following systems is this process at equilibrium?

1. A glass filled with water
2. A bottle of water after you poured half of the water out and recapped it.
3. A zip lock bag filled with water (no air).
4. Air in a zip-lock bag.

The water could be tap water or pure water. Answers that make reference to the definition of equilibrium or make use of kinetic or thermodynamic arguments would be great, so would answers to make reference to observations we make in our daily lives (i.e. outside a chemistry lab).