why are standards of mass necessary?

Answer 1

Every other fundamental unit is defined by natural phenomenon, that can be measured.

Mass is the only unit that does not have a way to independantly determine "mass-ness". (But scientists *are* working on it and have come up with a few ideas).

Examples:
Standard Amperes can be measured by forcing current through wires and measuring Force on the wires.

Standard Seconds can be measured by counting oscillations of excited states of certain atoms.

Standard Meters can be measured by counting waves (as in, wavelengths) of certain atoms in a special chamber .

All other standard fundamental units have independant ways to measure their values, but standard mass doesn't have a good way, yet, so they keep standard masses in vaults for reference.

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Answer 2

In order for there to be a system of order. A base unit is required so that arbitrary measurement mean something when compared relative to the base unit, standard unit. It gives other measurements an identity so that they can be gauged on how small/big they may be...I hope thats helped...Good luck!!!

Answer 3

So i cant make up a unit of mass and use it for my science report

Answer 4

So that when you buy a kilogram of rice, you don't get cheated and they only give you half a kilogram.