1.Most covalent compounds  have relatively low melting points and boiling points
2.Covalent compounds usually have lower enthalpies of fusion and vaporization than ionic compounds
3.Covalent compounds tend to be more flammable than ionic compounds.
4.When dissolved in water, they don'tconduct electricity.

Properties of Covalent Compounds

Covalent compounds, also known as molecular compounds, are formed when two or more nonmetals share electrons in a covalent bond. These compounds have a unique set of properties that distinguish them from other types of compounds such as ionic compounds. Let's explore the properties of covalent compounds in detail.

1. **Low Melting and Boiling Points**: Covalent compounds generally have lower melting and boiling points compared to ionic compounds. This is because covalent bonds are relatively weaker than ionic bonds, which require more energy to break.

2. **Low Solubility in Water**: Many covalent compounds are insoluble or have low solubility in water. This is because water, being a polar molecule, can only dissolve other polar or ionic substances. Covalent compounds, consisting of nonpolar molecules, do not readily dissolve in water.

3. **Nonconductivity**: Covalent compounds are typically poor conductors of electricity in both solid and liquid states. This is because covalent compounds do not have free ions or charged particles that can carry an electric current.

4. **Low Hardness**: Covalent compounds are generally softer compared to ionic compounds. This is because the covalent bonds between atoms are relatively weaker and more flexible, allowing the compound to be easily scratched or deformed.

5. **Lower Density**: Covalent compounds tend to have lower densities compared to ionic compounds. This is because the atoms in covalent compounds are held together by shared electrons, resulting in a more dispersed structure.

6. **Odor and Color**: Covalent compounds often exhibit distinct odors and colors due to the presence of different atoms and functional groups. For example, various organic compounds have characteristic smells, and certain covalent compounds display vibrant colors in solution or solid form.

7. **Variable State of Matter**: Covalent compounds can exist as gases, liquids, or solids at room temperature, depending on the strength of the intermolecular forces. The weaker the intermolecular forces, the more likely the compound will be a gas or liquid.

8. **Low Electrical Conductivity**: Covalent compounds do not conduct electricity in their solid state, as there are no mobile charged particles. However, some covalent compounds, such as acids and certain organic compounds, can conduct electricity when dissolved in water or in molten form.

In summary, covalent compounds possess distinct properties such as low melting and boiling points, low solubility in water, nonconductivity, low hardness, lower density, odor and color, variable states of matter, and low electrical conductivity. These properties arise from the nature of covalent bonds and the arrangement of covalent compounds' molecules or atoms.