What difference in the property of two miscible liquids enables their separation by fractional distillation?

Name the property of one of the constituents which can be used to separate a mixture of salt and iodine.

Name the process you would use to separate a mixture of two miscible liquids (like acetone and water).

Name one pair of substances whose mixture can be separated by fractional distillation.

Name one pair of liquids which can be separated by using a separating funnel.