|MadSci Network: Engineering|
The question is a bit broad - there are a lot of "everyday materials", and pressure upon them would result in different things.
Generally speaking, every object compresses in volume somewhat when exposed to uniform pressure; the question I guess you would have is "how much". Also, chemical reactions change to favor different equilibrium states under different than STP pressures (standard temperature pressure), e.g. Le Chatlier's Principle, so if some stable chemical condition of the object exists at STP, there might be a chemical change of the object when exposed to higher pressures.
I would say though that generally, considering the maximum pressures attained at even the lowest depths, most solid and liquid objects (w/o gaseous pockets) would compress only slightly, and no appreciable chemical change would occur. (If you picked the object's composition carefully, with specialized materials, you could get such effects, but most ordinary objects, no).
All gaseous objects, or components, would reduce in volume proportionately to the depth and to the ambient temperatures (after equalizing at the ambient temperatures) close to change predicted by the ideal gas equation.
An "ideal gas" is one whose physical behavior is accurately described by
the ideal-gas equation:
The constant R is called the gas constant, where its value and units depend on the units used in determining P, V, n and T
Temperature, T, must always be expressed on an absolute-temperature scale (degrees K)
The quantity of gas, n, is normally expressed in moles
The units chosen for pressure and volume are typically atmospheres (atm) and liters (l), however, other units may be chosen.
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