Which physical parameter is an index of degree of compaction or looseness of soil?

Specific Volume is the physical parameter that is an index of the degree of compaction or looseness of the soil. The degree of compaction is determined as the ratio between the maximum dried density of soil from the tests of moisture density relations of soils and soil density measured in situ conditions.
Specific volume is a property of materials defined as the number of cubic meters occupied by one kilogram of a particular substance.