Because different substances have different weights per the same volume: a teaspoon of feathers is not = to a teaspoon of iron.
There are many calculators on the web.
v3
There are many calculators on the web.
v3
Probably because there is no perfect answer. YANC used to have the teaspoon weight of each compound. I was going to provide the link for you. However, it was just changed (1 month ago) based on volume = mass/density which does not account for dead space in volume measures. I contacted the author and explained the error.i keep getting different answers...