Question

If i have an inverted beaker with a volume of air in it, then i push the beaker into the water. The deeper the beaker get, the greater pressure will act on the trapped air right and it become decrease in volume but increase in density, does that right? So does this mean the density of water in deep sea has higher density than the water at the surface?

Answer 1

mostly, yes

Answer 2

No, because liquid cannot be compressed. Air can, which is why the trapped air bubble will get smaller with increasing depth (pressure). Why deep divers must be careful surfacing, a lungfull of air deep down would be many lungfulls of air near the surface (which means bad times). Ever made a cartesian diver?

Answer 3

liquids can't be compressed MUCH, but it can be compressed.

Answer 4

Certainly. For small changes in the density, the fractional change in density equals the change in pressure divided by the bulk modulus K:\[\frac{\Delta \rho}{\rho} \approx \frac{1}{K}\Delta P\]
The bottom of the Atlantic is about 25,000 feet down, and pressure increases about 1 atm per 33 feet of depth, so the pressure down there is about 760 atm or 76 MPa. The bulk modulus of water is about 2.2 GPa = 2.2 x 10^3 MPa, so plugging into our equation we find that the fractional increase in the density of water should be about 3.5%.

Answer 5

fair play! apologies @JFraser

Answer 6

no worries!