We know that: `"Density of substance =("Mass of substance ")/("Volume of substance ")`

Here Mass of substance = 50 g

And Volume of substance `=20 cm^(2)`

So Density of substance `=(50 g )/(20 cm ^(3))`

`=2.5 g cm^(-3)`

Since the density of substance `(2.5 g cm ^(-3)` is greater than the density of water `(1 g cm^(-3))`, therefore , the substance will sink in water .