# Water pressure and density relationship with temperature

### How does pressure affect density of fluid?

In this paper, the pressure dependence of these variables for different temperatures is evaluated from density measurements of water for pressures up to 8 kbar. Water has a higher density in the liquid state than the solid, so ice cubes float. We know that, for gases, the volume is directly proportional to temperature by. Therefore, if you lower water's temperature, it's density will increase until For a particular gas under constant pressure and constant number of moles. is the case, we will examine the relationship between water's density and temperature.

### Pressure and the Gas Laws

For this reason, columns of mercury, "hanging" in an inverted vacuum tube, can be used as practical instruments to measure atmospheric pressure see FigureLutgens and Tarbuck, If water were used instead of mercury, the height of the column equivalent to normal pressure would be The Gas Laws The example of the gas-filled balloon can also be used to explore the basic gas laws see also Appendix D, p.

In the following, lets assume that the balloon is tight, so that the amount or mass of air in it stays the same: With density being the ratio of mass per volume, the gas density of the balloon thus varies only with its volume when mass is held constant. If we squeeze the balloon, we compress the air and two things will happen: Since density is mass over volume, and the mass stays constant, the rise in density means that the volume of the balloon decreases: For two states of pressure P1, P2 and two corresponding volumes V1, V2this is stated mathematically: This in turn increases the rate at which the gas molecules bombard the skin of the balloon.

Cooling the balloon down again will make the balloon shrink. How can we explain this? Remember that liquid water and solid water have the same network of bonds.

Liquid water at 25 deg is so rapidly breaking bonds between H2O units and reforming them that extra water molecules get trapped inside the water lattice. This is the reason why liquid water is more dense than solid water.

The bonds in water break more slowly as temperature decreases and the structure tend to trap fewer extra water molecules. At low temperature, more of the water has the same lattice as ice. Wikipedia, Water Density It is possible to have liquid water at temperatures well below 0 deg C.

Molecules in this supercooled water are free to move. Bonds are made and broken. The long range structure is not perfect but the short range structure of supercooled water is very much like ice.

Adding a crystal to supercooled water causes instantaneous ice formation. It is similar to water in that it is polar, with a permanent dipole moment, and forms hydrogen bonds with itself.

### thermodynamics - Water pressure vs temperature - Physics Stack Exchange

It doesn't have the same type of 3-dimensional lattice that water has though. We can see that the density decreases with temperature through this range. Unlike the situation with water, there is no maximum density point.