what type of solid is formed for each of the substances: C2H5OH,CH4,CH3Cl,MgSO4 arrange these substance in order of increasing melting point?

Melting point : CH₄ < CH₃Cl < C₂H₅OH < MgSO₄

MgSO₄ has giant ionic structure in which the opposite ions of Mg²⁺ and SO₄²⁻ are held together by strong electrostatic attractions. The other 3 compounds have simple molecular structure in which the molecules are held together by intermolecular forces which is weaker than the stronger electrostatic attractions in MgSO₄. Hence, MgSO₄ has the highest melting point.

C₂H₅OH molecules are held together by hydrogen bonds which is the strongest intermolecular forces for small molecules. Hence, C₂H₅OH has the second highest melting point.

CH₃Cl molecule is polar, and thus CH₃Cl molecules are held together by dipole-dipole attractions. CH₄ molecule is non-polar, and thus CH₄ molecules are held together by instantaneous dipole - induced dipole attractions (London forces). The former are stronger than the latter. Hence, CH₃Cl has a higher melting point than CH₄.