density = mass/volume

[rdabke]

Is it true that X ml. of water weighs X mg,

but X ml of other substances denser than water weighs more than X mg (directly proportional to its density)?

[Guest]

No, 1 mL of water weighs (approximately) 1 g, or 1 L of water about 1 kg. At 4 degrees C, the maximum density of water occurs and weight is 0.999 973 g/mL. Except for extreme accuracy, that is ~1.

Water expands with increasing temperature. At 25 degrees C, densitu is 0.996783 g/mL.

Items which are denser than water weigh more than 1 g/mL

[rdabke]

So then, how does 1 fl. oz of water weight 1 oz.?

[Guest]

In the US gallon, it doesn't. 1 US gallon is about 8.33 lbs, and divided into 128 fluid ounces, so it is about 1.04 av. oz.

The Imperial gallon, of 160 oz, is defined as 10 lbs of water,
so 10 lbs/gal x 16 oz/lb x 1gal/160 oz works out to 1 av oz/ Imp. fl. oz.