What are Van der Waals forces?

Van der Waals forces are indeed attractions that occur between molecules, specifically involving temporary or permanent dipoles. These forces arise when atoms or molecules exhibit charged ends due to uneven distribution of electrons, leading to weak intermolecular attractions. Often, these forces are referred to in the context of interactions between neutral molecules or between different parts of a single large molecule.

The concept of charged ends relates to the strength of these attractions; for instance, in polar molecules, the positive end of one molecule can be attracted to the negative end of another. This phenomenon plays a crucial role in determining the physical properties of substances, including boiling and melting points, and contributes to the interactions in biological systems.

The other choices do not correctly describe Van der Waals forces. They do not only attract unlike materials, they are relevant in many environments, not just in vacuums, and are not directly related to temperature conditions, such as high temperatures.