What is the difference between density and specific gravity? Select all correct answers. Density and specific gravity are exactly the same Density describes the relative mass of a material based on the volume of the material while specific gravity compares the weight of a material compared to the weight of the same volume of water Specific gravity can only be measured for an oven dry sample while density can be measured in all four moisture states Density is unitless, while specific gravity has units of mass/volume Specific gravity is a measure of the weight of a material relative to the same volume of water while density is independent of the properties of water Specific gravity can only be calculated from density given in Sl units What is the difference between apparent density and bulk density? Select all correct answers. Apparent density is the mass per unit volume of the impermeable portion of the aggregate particles The sample volume used for apparent density includes the volume of the small pores on the surface of the aggregate (so solid material + surface voids = total aggr volume) The sample volume used for bulk density includes the volume of the small pores on the surface of the aggreagte The sample volume used for apparent density excludes the volume of the small pores on the surface of the aggreagte - only the solid portion of the aggregate is included as aggregate volume. Apparent density is the closest to the 'real' density of the material: mass/solid volume that we typically measure.