Which is heavier 1 kilogram or 2 pints of fluid?

Answer 1

That all depends on what the fluid is.

If the fluid is air, then 1 kg is much heavier than 2 pints of it.

If the fluid is water, then 1 kg has roughly the same weight as 2 pints of it.

If the fluid is mud or molten lead, then 1 kg weighs much less than 2 pints of it.