Loading ...
Sorry, an error occurred while loading the content.

THANKS: Aargh, chemistry!

Expand Messages
  • Simon Vollam
    Morning List, Thanks for all your helpful comments and suggestions. It turns out - as I expected - that the author was referring to the mass of a particular
    Message 1 of 13 , Jul 2, 2001
    • 0 Attachment
      Morning List,

      Thanks for all your helpful comments and suggestions.

      It turns out - as I expected - that the author was referring to the
      mass of a particular gas produced by burning a known amount of
      material (for example, mg of HCN per g of polyurethane foam). This is
      commonly referred to in combustion science as the yield. I agree that
      it is not a yield in the normal chemistry context, i.e. the amount of
      a substance actually produced in a chemical reaction relative to the
      amount predicted theoretically from the reaction stoichiometry. But
      it's a similar concept.

      The author tells me that he wished to stress the fact that it was a
      mass of gas, and not the volume concentration in air. However, I
      wonder whether "vytezek" has a narrower scientific meaning in Czech
      than "yield" does in English. BTW I agree that "amount" is more
      appropriate than "quantity" in this context.

      To answer the mass-vs-weight query, I was always taught that,
      strictly speaking, mass is measured in grammes whereas weight (being
      a force) is measured in Newtons. A man on the moon, for example,
      weighs much less than on earth, but his mass is the same regardless
      of location (relativistic considerations aside).

      On the other hand, strictly speaking one should say "ethanol", not
      "ethyl alcohol", but who cares? Not many chemists do their
      experiments extraterrestrially, and one often sees "weight" used in
      scientific papers as a synonym for mass, especially outside physics.

      Enough, enough. I'm an economist now.

      Thanks again,

      Simon
    • Rachel Thompson
      ... Hi Petr, In normal speech, weight is still the commoner way of expressing what is more correctly termed mass. But I ve never used it as an equivalent for
      Message 2 of 13 , Jul 2, 2001
      • 0 Attachment
        > Docela by mne zajimalo, jestli se v anglictine ujalo vedecky
        > spravnejsi "mass", nebo jestli chemici dodnes pouzivaji
        > beznejsi "weight". Byl jsem zvykly prekladat "hmotnost" jako "weight"
        > (napriklad "wt.%") ale trebas je to uz dnes zastarale. (Rachel to asi
        > bude vedet.)

        Hi Petr,

        In normal speech, weight is still the commoner way of expressing what is
        more correctly termed mass. But I've never used it as an equivalent for
        mass in a chemical text. Until now, I'd have said that that usage was
        out of date, but checking for "weight percent" on Google does bring up
        14,000 hits, so I guess it is still used (perhaps especially in
        America). We always used percentage mass in Britain.

        Rachel
      • Simon Vollam
        ... We always used percentage mass in Britain. I m not sure we always did. Things are much more standardised now, though. Simon
        Message 3 of 13 , Jul 2, 2001
        • 0 Attachment
          --- In Czechlist@y..., "Rachel Thompson" <rachel.thompson@s...> wrote:
          We always used percentage mass in Britain.



          I'm not sure we always did. Things are much more standardised now,
          though.

          Simon
        • Rachel Thompson
          ... Then I suppose it must be a very recent standardisation -- you re not that much older than me, are you? By the time we started doing percentage mass
          Message 4 of 13 , Jul 2, 2001
          • 0 Attachment
            > I'm not sure we always did. Things are much more standardised now,
            > though.

            Then I suppose it must be a very recent standardisation -- you're not
            that much older than me, are you? By the time we started doing
            percentage mass calculations at A-level, everything was "mass" in all
            the course literature, and I'd never heard of this "weight percent"
            until I looked it up this morning.

            But to Petr and others who are wondering what to use, I'd suggest that
            mass is probably the safer bet, since it is more strictly correct.
            Would you go along with that?

            Rachel
          • Simon Vollam
            ... not ... No, only a couple of months older, I would estimate. Seriously, though, I think the SI/IUPAC standardisation efforts have only recently begun to
            Message 5 of 13 , Jul 2, 2001
            • 0 Attachment
              --- In Czechlist@y..., "Rachel Thompson" <rachel.thompson@s...> wrote:
              > > I'm not sure we always did. Things are much more standardised now,
              > > though.
              >
              > Then I suppose it must be a very recent standardisation -- you're
              not
              > that much older than me, are you?

              No, only a couple of months older, I would estimate. Seriously,
              though, I think the SI/IUPAC standardisation efforts have only
              recently begun to bite. When I was studying chemistry in the late
              1980s, many of the older professors got decided uppity when we
              corrected their "antiquated" terminology.

              Just out of interest,were you taught to use "molecular mass" or
              "molecular weight"?

              > But to Petr and others who are wondering what to use, I'd suggest
              that
              > mass is probably the safer bet, since it is more strictly correct.
              > Would you go along with that?

              Yes indeed, as a rule of thumb. But don't be too surprised if some
              grey-haired chemist tries to correct you!

              Simon
            • Rachel Thompson
              ... Mass. We had some confusion between molar mass and molecular mass , but it was always mass, not weight. Rachel
              Message 6 of 13 , Jul 2, 2001
              • 0 Attachment
                > Just out of interest,were you taught to use "molecular mass" or
                > "molecular weight"?

                Mass. We had some confusion between "molar mass" and "molecular mass",
                but it was always mass, not weight.

                Rachel
              • Simon Vollam
                ... mass , ... Interesting. Molecular mass sounds quite alien to me, although I ve nothing against it. It seems those few short months between us have seen
                Message 7 of 13 , Jul 2, 2001
                • 0 Attachment
                  --- In Czechlist@y..., "Rachel Thompson" <rachel.thompson@s...> wrote:
                  > > Just out of interest,were you taught to use "molecular mass" or
                  > > "molecular weight"?
                  >
                  > Mass. We had some confusion between "molar mass" and "molecular
                  mass",
                  > but it was always mass, not weight.
                  >
                  > Rachel

                  Interesting. Molecular mass sounds quite alien to me, although I've
                  nothing against it. It seems those few short months between us have
                  seen significant changes.

                  I suggest that anyone wishing to find out the currently approved
                  nomenclature visit the IUPAC site
                  http://www.iupac.org/reports/1993/homann/index.html

                  BTW this gives both molecular mass and molecular weight (mind you, it
                  was last updated in 1993 - what have they been doing since then?)

                  Simon, enjoying this trip down (failing-)memory lane
                Your message has been successfully submitted and would be delivered to recipients shortly.