Short answer: 10 kg in 0.5 m³ is 20 kg/m³ — 0.02 g/cm³, which is lighter than cork. Conversely 1,000 kg/m³ (water) over 0.002 m³ gives a mass of 2 kg.
Reading the three-unit answer
kg/m³ is the SI form, g/cm³ is the chemistry form (and is numerically equal to grams per millilitre), and lb/ft³ is the engineering form. All three describe the same material; the numbers look wildly different only because the units are.
Worked example
A steel block measures 0.1 m × 0.1 m × 0.1 m, so its volume is 0.001 m³. At 7,850 kg/m³ its mass is 7.85 kg. The same block in aluminium at 2,700 kg/m³ weighs 2.7 kg — the comparison the density figure exists to make.