What is the mass of 1 teaspoon full of protons?
This question is not very well defined: the problem is that you didn’t specify how you “pack” the protons in the teaspoon. The mass of the proton is about 1.67E-27kg. The proton is not a solid sphere, it is a composite particle that consists of quarks and gluons interacting with each other. Still, we can approximate the volume of the proton as 1E-15m. The volume of a teaspoon is 5ml = 5E-6m^3, so you can theoretically fit 5E-6 / (4*pi*(1E-15)^3/3) = 1.2E39 protons in a teaspoon. This is only assuming that you can actually squeeze them together so that there is no space between them. In this case the mass would be 1.2E39*1.67E-27kg = 2E12kg. (quite a heave teaspoon).
