The mass of 254 mL of water is 254 g. Since the density of water is 1g/mL, we can simply multiply the density 1g/mL by 254 mL of water and get 254 g as our answer. Since mL is in the numerator and denominator, mL cancels out and we are left with g only.
<span>Mass is a property that determines how much effort it takes to change somethings velocity. Weight is how much downward force does something exert in a gravitational field which is just the amount of gravity time the mass of an object. We use mass interchangeable with weight because everything on earth experiences the same amount of gravity or close to it, and so something that weighs twice as much as something else also has twice as much mass as that something else. Weight can actually vary for the same mass here on earth the strength of gravity changes from one place to another by small amounts, not enough to ruin your cooking recipe instructions, and weight can change dramatically for something that is falling, the strength of gravity for astronauts in orbit is not much reduced in comparison to here on earth, if there was no gravity they wouldn't go around the earth, they are weightless because they are falling and have enough sideways velocity to keep missing the earth, but their mass has not changed, it still requires effort to get them moving or to stop them.
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