Covalent compounds exhibit low melting and boiling points primarily due to the presence of weak intermolecular forces.

Covalent compounds, also referred to as molecular compounds, are formed when two non-metal atoms come together to share electrons, resulting in the creation of a covalent bond. The strength of a covalent bond is influenced by the degree of overlap between the atomic orbitals and the sharing of the electron pair. In contrast, the interactions between these molecules, known as intermolecular forces, are relatively weak when compared to the strong covalent bonds that hold the molecules together.

The melting and boiling points of a substance are determined by the strength of the forces acting between its constituent particles. For covalent compounds, these forces are the aforementioned weak intermolecular forces, rather than the strong covalent bonds. When a covalent compound is heated, it is primarily these weak intermolecular forces that are overcome, allowing the substance to transition from a solid or liquid state to a gaseous state. Consequently, less energy (in the form of heat) is required to disrupt these forces, resulting in relatively low melting and boiling points.

There are three primary types of intermolecular forces: London dispersion forces, dipole-dipole interactions, and hydrogen bonding. London dispersion forces are the weakest and are present in all covalent compounds. Dipole-dipole interactions occur in polar covalent compounds, while hydrogen bonding, which is the strongest of the intermolecular forces, takes place in compounds where a hydrogen atom is bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine. Despite being the strongest intermolecular force, hydrogen bonding remains significantly weaker than covalent bonds.

In conclusion, the low melting and boiling points of covalent compounds can be attributed to the weak intermolecular forces that hold the molecules together. These forces are substantially weaker than the covalent bonds within the molecules, which explains why less energy is needed to overcome them, ultimately leading to lower melting and boiling points.