A solid is soft and has a low melting point (below \(100^{\circ} \mathrm{C}\) ). The solid, its melt, and a solution containing the substance are all nonconductors of electricity. Classify the solid.

Covalent compounds are substances where atoms are bonded together by sharing pairs of electrons. These shared electrons form the covalent bonds that hold the atoms together. Because of this specific type of bonding, covalent compounds exhibit a range of characteristic properties that distinguish them from other types of substances.

Softness and Strength of Covalent Bonds

One key characteristic is the generally soft nature of these compounds when they are in their solid state. This is because the forces between molecules are relatively weak compared to the strong covalent bonds within the molecules. As such, it does not require a lot of energy to separate the molecules, and hence, covalent compounds are often soft and easy to deform.

Energy Considerations and Melting Points

Low melting points are another hallmark of covalent compounds. Since the intermolecular forces are not very strong (like Van der Waals forces), the energy required to disrupt these interactions and change the state from solid to liquid is low. This means that covalent compounds typically melt at temperatures below 100 degrees Celsius, much lower than ionic or metallic compounds.

Another characteristic of covalent compounds is that they are nonconductors of electricity in all states of matter—solid, liquid, and solution. Electricity requires the movement of charged particles to flow, and in the case of covalent compounds, there are no free ions or electrons available to support this movement. In a solid state, the electrons are tightly held within covalent bonds and do not have the freedom to move. Likewise, when a covalent compound is melted or dissolved, it still does not produce ions, which are the charge carriers in ionic compounds that enable them to conduct electricity. This distinguishes covalent compounds starkly from ionic substances and metals, which do conduct electricity in specific states (ionic compounds when melted or dissolved, and metals in solid form due to the presence of delocalized electrons).

Substances with low melting points typically have relatively weak forces holding their particles together. These forces can be of different types, such as hydrogen bonds, dipole-dipole interactions, or London dispersion forces. In the context of molecular solids, which are often made up of covalent compounds, these intermolecular forces are not particularly strong. This leads to a low amount of energy being needed to overcome these forces, thus resulting in low melting points.

Understanding the significance of low melting points can facilitate the prediction and explanation of a substance's physical properties. For instance, such substances are generally more flexible and less durable than high melting point materials. Their applications therefore often exploit their softness and low melting behavior, such as the use of certain waxes and plastics.