The difference in melting points between copper(II) chloride (CuCl₂) and ethane (C₂H₆) comes down to the types of bonds and intermolecular forces present in each substance:

Copper(II) Chloride (CuCl₂):

It’s an ionic compound.

Ionic compounds are held together by strong electrostatic forces between positively charged copper ions (Cu²⁺) and negatively charged chloride ions (Cl⁻).

These strong ionic bonds require a lot of energy to break, hence the high melting point.

Ethane (C₂H₆):

It’s a covalent compound.

Covalent compounds are held together by shared electrons between atoms.

Ethane is a nonpolar molecule, meaning it primarily experiences weak van der Waals forces (specifically, London dispersion forces) between its molecules.

These intermolecular forces are much weaker than ionic bonds, requiring significantly less energy to overcome, resulting in a low melting point.

In summary:

Strong ionic bonds in CuCl₂ = high melting point.

Weak van der Waals forces in C₂H₆ = low melting point.