Is the mass of 1 liter of feathers greater than the mass of 1 liter of nails?

No. The mass of one liter of feathers is not greater than the mass of 1 liter of

nails. The mass of 1 liter of nails is greater than the mass of 1 liter of feathers.

That's why 1 liter of nails is heavier than 1 liter of feathers.