keesom造句

• Also Keesom interactions are very weak van der Waals interactions and do not occur in aqueous solutions that contain electrolytes.
• The Keesom interaction can only occur among molecules that possess permanent dipole moments a . k . a . two polar molecules.
• Onnes'student Willem Hendrik Keesom was eventually able to solidify 1 cm 3 of helium in 1926 by applying additional external pressure.
• The strength of the dipole induced dipole interactions can be modeled with a combination of Debye, Keesom and London interactions through addition.
• These forces dominate the interaction of non-polar molecules, and are often more significant than Keesom and Debye forces in polar molecules.
• The dispersion ( London ) force is the most important component because all materials are polarizable, whereas Keesom and Debye forces require permanent dipoles.
• These intermolecular screening forces are also known as Van der Waals forces, which is determined by the Keesom, Debye and London Dispersion forces.
• The energy of a Keesom interaction depends on the inverse sixth power of the distance, unlike the interaction energy of two spatially fixed dipoles, which depends on the inverse third power of the distance.
• :: Forces " stronger " than London dispersion forces that are also van der Waals include Debye forces, Keesom forces, hydrogen bonds, ionic bonds and induced ion forces; see intermolecular force.
• These differences can be very small, as in the case of the boiling point of straight-chain alkenes, such as dipole dipole forces ( or Keesom forces ), which add to the London dispersion forces and raise the boiling point.
• These positive and negative poles may be a permanent property of a molecule ( Keesom forces ) or a transient effect which can occur in any molecule, as the random movement of electrons within the molecules may result in a temporary concentration of electrons in one region ( London forces ).
• Returning to nomenclature, different texts refer to different things using the term " van der Waals force . " Some texts describe the van der Waals force as the totality of forces ( including repulsion ); others mean all the attractive forces ( and then sometimes distinguish van der Waals-Keesom, van der Waals-Debye, and van der Waals-London ).