Final answer:
The property of a liquid that changes with depth, leading to varying pressure, is density. This is because the weight of the liquid above increases with depth, influencing the pressure at lower levels. For most liquids, like water, density is considered relatively constant and the pressure increases with depth.
Step-by-step explanation:
This is because as you go deeper into a liquid, there's more liquid above that point, exerting weight due to the gravitational force. Since pressure is the force exerted per unit area, this added weight from the liquid increases the pressure. While the density of liquids, like water, is often considered constant at different depths due to their incompressibility, in some instances, like in the atmosphere, density can change with altitude. In the case of a swimming pool, we can consider the density of water to be constant with depth. The pressure at any point is determined only by the depth of the fluid's surface and the density of the fluid. This concept is described by the hydrostatic pressure formula, which shows that pressure increases with depth due to the weight of the liquid above that point. Therefore, pressure in a static fluid such as a liquid varies with depth because of the increasing weight of the fluid above the point being measured, which is directly related to the fluid's dense layer exerting force due to gravity. This understanding is crucial when calculating pressure at different depths for a fluid of constant density, such as in most liquid applications.