What happens in the molecular structure of a liquid (imcompressible)?

In summary: However, since the milk is falling, the bulk motion is negligible and the temperature at the bottom will be greater than the temperature at the top.
  • #1
MagnusChases
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Suppose you have a liquid with high potential energy at a height [H] in a first moment. In a second moment, the liquid loses its potential energy (that is converted into kinetic energy) and fall in a cylinder at height [h] .IF the liquid is incompressible what happens with the molecules in the cylinder's base(Does the temperature rises up a little, because of the kinetic energy? How does the pressure rise up, if the liquid is incompressible?I am an undergraduate student and was discussing this problem with my colleague. Something important is missing. (Maybe we are having a problem because it is a liquid, not a gas)

Thanks for your help.
 
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  • #2
So you have a glass of incompressible milk on the edge of the table and the cat comes and pushed the glass off.
Does the temperature of the milk rise as its falling?
 
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  • #3
256bits said:
So you have a glass of incompressible milk on the edge of the table and the cat comes and pushed the glass off.
Does the temperature of the milk rise as its falling?

Yes. When the milk falls in the cylinder, will the temperature of the bottom be greater than the surface? What causes the pressure in the bottom given the initial conditions(liquid incompressible)?
 
  • #4
MagnusChases said:
Yes. When the milk falls in the cylinder, will the temperature of the bottom be greater than the surface? What causes the pressure in the bottom given the initial conditions(liquid incompressible)?
What causes the pressure - the weight of the fluid above.

For an incompressible fluid P2 = P1 + γh = P1 + ρgh
where P2 is the pressure at the depth h, P1 is the pressure at the top, γ is the specific weight and is a constant for incompressible fluids - the density does not change, nor the volume. We also assume g, gravity, is a constant for the difference in elevation.

When the fluid drops, it is in free fall, there is no pressure difference between top and bottom, the density and gamma and volume are the same as the initial condition of right before the fall.

With these assumptions, should the temperature at the bottom and top differ during free fall, from before, or not?

I think what is bothering you is the ideal gas equation. PV = nRT.
If P2 is different from P1, and the volume is constant, then the only other STATE variable that can change is T, thus T2 is different from T1.
I capitalized a hint.

You might find more hints here, between compressible and incompressible fluids.
http://users.metu.edu.tr/csert/me582/ME582 Ch 01.pdf
PS - I won't be back for a quite a few hours, so perhaps someone else will chime into help you out.
 
  • #5
MagnusChases said:
When the milk falls in the cylinder, will the temperature of the bottom be greater than the surface?
To be clear, we are talking about a glass of un-disturbed milk in free fall in mid-air as it approaches the floor? We are not talking about the milk after the glass has shattered and the milk is still splashing?

The temperature of the milk relates to the average kinetic energy of its component molecules in the frame of reference where there is no net momentum.

Technically, the sort of temperature described above is "static temperature". One can also consider "total temperature" which includes the kinetic energy from the bulk motion of the fluid.
 

Related to What happens in the molecular structure of a liquid (imcompressible)?

1. How does temperature affect the molecular structure of a liquid?

The temperature of a liquid affects the molecular structure by increasing the kinetic energy of the molecules, causing them to move more rapidly and further apart. This leads to a decrease in intermolecular forces and a more disordered structure.

2. What role do intermolecular forces play in the molecular structure of a liquid?

Intermolecular forces, such as hydrogen bonding, dipole-dipole interactions, and London dispersion forces, determine the arrangement of molecules in a liquid. These forces are responsible for the cohesive and adhesive properties of liquids.

3. How is the density of a liquid affected by its molecular structure?

The density of a liquid is determined by the spacing and arrangement of its molecules. A more compact and ordered molecular structure will result in a higher density, while a less ordered structure will lead to a lower density.

4. Can the molecular structure of a liquid change?

Yes, the molecular structure of a liquid can change under different conditions such as temperature, pressure, and the presence of other substances. For example, water can exist as a liquid, solid, or gas depending on the temperature and pressure.

5. How does the molecular structure of a liquid differ from that of a solid?

The molecular structure of a liquid is less ordered and more dynamic compared to a solid. In a liquid, the molecules are able to move and flow past each other, while in a solid, the molecules are tightly packed and vibrate in a fixed position.

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