Boiling point order: RI > RBr > RCl > RF (higher MW → stronger London forces) For same halogen: Longer chain → higher bp (more surface area)

Density: CH2Cl2, CHCl3, CCl4, CH2Br2, bromoform, iodomethane are ALL denser than water. Lower alkyl chlorides (CH3Cl, C2H5Cl) are less dense than water.

Polarity: C-F and C-Cl bonds are quite polar. C-Br and C-I less so (larger, more polarizable atoms). But dipole moment also depends on molecular geometry.

Environmental concerns: CFCs (Freon) destroy ozone layer. DDT is non-biodegradable. These are commonly tested in JEE theory questions.