Geometrical Isomerism ($$cis/trans$$ & $$E/Z$$)

Dipole moment $$(\mu)$$: cis > trans;

In the cis isomer, polar bond dipoles reinforce each other, giving a net non-zero dipole moment ($$\mu \neq 0$$). In the trans isomer, opposing bond dipoles cancel each other out due to symmetry ($$\mu \approx 0$$).

Boiling Point: cis > trans;

Higher dipole moment in the cis isomer leads to stronger intermolecular dipole-dipole attractions, requiring more thermal energy to boil.

Melting Point: trans > cis

Melting point depends strongly on how well molecules pack into a solid crystal lattice. The more symmetrical trans-isomer fits together and packs much more tightly, resulting in stronger intermolecular forces in the solid state.