Final answer:
In a water column, 'isopycnic' means having the same density with depth, 'isothermal' means having the same temperature with depth, and 'isohaline' means having the same salinity with depth. Pressure at a depth in a fluid of constant density is calculated based on atmospheric pressure and the weight of the fluid above it. Density changes with temperature, which affects the state of water and buoyancy-related phenomena.
Step-by-step explanation:
If a water column has the same density with depth, it is said to be isopycnic. If it has the same water temperature with depth, it is isothermal. If it has constant salinity over depth, it is isohaline. These terms are important in understanding the characteristics of water columns, which are relevant to oceanography and physics.
The pressure at a depth in a fluid of constant density is determined by the atmospheric pressure plus the pressure due to the weight of the fluid above the point of interest. Using the hydrostatic pressure equation, we can calculate the pressure given the fluid's density and the depth. The equation holds true for liquids since they are nearly incompressible and even to a certain extent for gases, as long as the density does not change much within the depth considered.
Heating and cooling of water can change its density, since density varies with temperature. This in turn impacts the state of the water, whether it will be in solid, liquid, or vapor form. A basic understanding of these matters is crucial when addressing questions like water buoyancy and floating, where the density of the object compared to the fluid's density is key.