Boiling Point & Van der Waals Force: Weight Dependency

[phymatter]

1.Why does boiling point depend on weight ?
2.Does the vanderwall force depend on weight ?

 

[Ygggdrasil]

1. Because dispersion forces (a type of van der Waals force) depend on molecular size.

2. Dispersion forces (also known as induced dipole-induced dipole interactions) depend on the polarizability of the molecule (how easy it is to get an asymmetric distribution of electron in a molecule). As the number of electrons in a molecule and the size of the molecule increases, the polarizability increases.

 

[quicknote]

1. The boiling point of a substance is directly related to its intermolecular forces, which are the attractive forces between molecules. These forces are dependent on the weight, or molecular mass, of the molecules. As the molecular mass increases, the intermolecular forces also increase, making it more difficult for the molecules to break apart and enter the gas phase. Therefore, substances with higher molecular masses will have higher boiling points.

2. The van der Waals force, also known as London dispersion force, is one type of intermolecular force that is dependent on the weight of the molecules. This force is caused by temporary dipoles that occur due to the constant motion of electrons in molecules. As the molecular weight increases, the number of electrons also increases, leading to stronger and more frequent interactions between molecules. This results in a stronger van der Waals force. Therefore, the van der Waals force does depend on weight, as it is directly related to the molecular mass of the substances involved.