Electric Field Effect on Water

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Discussion Overview

The discussion centers around the effects of an electric field on the attractive forces between water molecules, particularly in the context of a research project. Participants explore theoretical models, calculations, and the implications of molecular dipoles in the presence of an electric field.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in calculating the attractive force between water molecules under an electric field and seeks assistance.
  • Another participant suggests modeling water molecules as dipoles to analyze the situation.
  • A further contribution notes that while an electric field does not exert a net force on a water molecule, it may align the molecules, leading to a complex n-body problem regarding their interactions.
  • It is mentioned that pure water typically consists of multiple H2O units and that an electric field does not change the number of these units, but rather influences oxidation/reduction reactions in water.
  • One participant elaborates that an electric field will polarize water molecules, altering their dipole moments and orientation, and that calculating interaction energy requires knowledge of the polarizability of water and the geometry of the molecules.
  • Specific interaction energy values are discussed, with a reference to the energy of hydrogen bonds and how electric field orientation can affect these interactions.

Areas of Agreement / Disagreement

Participants express varying views on the effects of electric fields on water molecules, with no consensus reached on the specific calculations or implications of these interactions.

Contextual Notes

Participants highlight the importance of assumptions regarding molecular geometry and the need for specific parameters such as polarizability and electric field strength, which remain unresolved in the discussion.

Daniel_H_S
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I'm trying to calculate the attractive force between two Water Molecules under the effect of an Electric field and I'm completely stumped. Its part of a research project I'm doing at my new work, I'm sure I'm just forgetting a formula for it from somewhere, I'm sure I remember covering this sort of effect at uni. Any help would be greatly appreciated.
 
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You might try modeling each molecule as a dipole.
 
as manchot said, water molecules can be approximated (to fairly good accuracy) as dipoles.

The electric field will of course exert no net force on a water molecule; so i assume you mean the force between water molecules after they have all been aligned? If so, this will turn into a n-body problem (of sorts)... i think the details of your situation are pretty important.
 
Pure water normally has molecules that contain 1 through 9 or more H2O units. A small electric field does not influence the number of H2O units in a molecule.

Normally, an electric field is used to cause oxidation / reduction reactions of stuff within water, for example: electrolytic coating and galvanic cell processes. Pure water is dielectric material. Ionization energy applies to a single H2O.

Perhaps if you provide more detail as 'attractive force', someone can provide a less nebulous response.
 
It is not a trivial problem. An electric field will polarize the molecules, changing their dipole moment and also orienting it. To find the interaction energy you need to know the polarizability of a water molecule in vacuum (a 3d tensor) and also you need to know the polarization of your electric field. Once you knwo this you will need to asume a geometry for the water molecules and then you can calculate it. a dime of waters (2 water molecules in an optimal configuration) in vacuum has an interaction energy of the order of 250 meV. This is the energy o a hydrogen bond. An electric field polarized in the direction of the Hbond will make this interaction stronger (how much, this depends on the polarizability (alpha) and on the electric field). Polarized perpendicular to the Hbond direction will make the Hbond weaker. Again, how much it depends on those two quantities.

Hope this helps!
 

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