Surface Tension Forces: Physics & Intermolecular Forces

[shamstar]

i'm looking into the physics behind surface tension, and am a little confused about the intermolecular forces that act on the liquid. I understand that hydrogen bonding occurs because of the positive and negative atoms in a water molecule. However, i am unsure of exactly what other forces occur. i keep coming across things like intermolecular, van der waals, london dispersion and cohesive. What are all the forces exactly? thanks

 

[Morga]

From what i know:

Hydrogen bonding : Occurs between Hydrogen atoms and atoms of oxygen, fluorine and nitrogen. It is the strongest out of the three intermolecular forces listed here. Hydrogen bonds pull the molecules of water outwards, resulting in water being less dense when frozen than when in a liquid state.

Dipole-dipole : This occurs between molecules with an uneven charge distrubtion. The opposite charges attract one another creating a bond.

Van Der Waals : This is an induced dipole-dipole attraction which occurs when the distribution of electrons in an atom become unevenly spread, resulting in a uneven charge distribution. This results in neighboring atoms electrons to fluctuate. The uneven distribution of charge allows the opposite charges to attract. This is the weakest of the three.

Van Der Waals occurs in all substances. Dipole-dipole occurs only in polar molecules. Hydrogen Bonding occurs only between hydrogen atoms in a molecule and the atoms of either oxygen, nitrogen or fluorine in another.

 

[charng]

Surface tension is a phenomenon that occurs due to the intermolecular forces between molecules in a liquid. These forces are responsible for the cohesive property of liquids, which allows them to resist external forces and maintain their shape. The most well-known intermolecular force in water is hydrogen bonding, which occurs between the positively charged hydrogen atom of one water molecule and the negatively charged oxygen atom of another water molecule.

In addition to hydrogen bonding, there are other intermolecular forces that contribute to surface tension. These include van der Waals forces, which are weak attractive forces between all molecules, and London dispersion forces, which are temporary dipole-dipole interactions between nonpolar molecules. These forces play a role in determining the strength of surface tension in a liquid.

Cohesive forces, on the other hand, refer to the attractive forces between molecules of the same substance. In the case of water, cohesive forces between water molecules contribute to the high surface tension of water. This is because the hydrogen bonding between water molecules is relatively strong, leading to a high degree of cohesion.

Overall, surface tension is a complex phenomenon that is influenced by various intermolecular forces. The exact contribution of each force depends on the specific properties of the liquid, such as its molecular structure and polarity. Understanding these forces is crucial for studying the physics of surface tension and its effects on various processes, such as capillary action and droplet formation.