On 2007 May 6 , at 12:09 PM, Mike Millet wrote:
... useful ... (for people to) know that the one liter bottles of
soda or water ... are one kilo. ... it at least helps them equate
mass and volume ...
The first point is a good one but I'd be careful of the second one.
Yes, it is true that one litre of water has a mass of one kilogram,
one litre of soda has a mass of one kilogram only because soda is
mostly water.* It is not true for most other materials.
And we need to be careful NOT to "equate" mass and volume as Mike
wrote. I'm sure Mike didn't mean it that way, but in presenting such
information to less informed people, it is necessary to make sure
that they aren't led to think that volume and mass are the same
thing. We may say that volume and mass are "related" but I think
"equated" gives a false impression. It is most certainly NOT true
that "1 L = 1 kg".
While it IS true that one litre of WATER will HAVE A MASS of one
kilogram:
1. it is NOT true that 1 L of anything else will have a mass of
1 kg (unless that something else is composed mostly of water or is
some other material that coincidentally has the same density as water);
and
2. it is NOT true that 1 kg is EQUAL to 1 L in general (for
water or anything else).
Regards,
Bill Hooper
Fernandina Beach, Florida, USA
* The litre bottle of soda (or water) will have a mass of 1 kg only
if we can also ignore the mass of the bottle, but that is probably OK
for the plastic bottles usually used.
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SImplification Begins With SI.
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