They use size and weight
Some ways that industry and agriculture use physical properties to separate substances are as follows-
a)Separation based on the difference in DENSITY – In the process of sedimentation, the heavier particle settles at the bottom while the lighter particle remains dissolved or float in the solvent. The settled heavier substance is then removed periodically. For example mud and sand impurities from water are removed through this process.
b)Separation based on the difference in SOLUBILITY – Some substances that remain un dissolved in any other substance can be easily removed through the process of filtration. For example – Extraction of coffee from grounds
c)Separation based on the difference in Special metal Property – Iron possesses magnetism and thus it can be easily separated from nonmagnetic substances
d)Separation based on the difference in Vapour pressure/Boiling Point – It is the concept behind the process of separation through Distillation. In distillation, liquid with the lower boiling point boils first which is collected through condensation while the liquid with higher boiling point remain in the flask.