Density of gold is 19.3 g/cm3. Density (by the definition) is mass per unit of volume:
D = m/V (D - density, m - mass, V - volume)
If one side of the cube is 2 cm, then the its volume is 23 cm3 = 8 cm3. Thus
D = 500 g/8 cm3 = 62.5 g/cm3 - it is too heavy for gold.
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