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TGL5:
Atoms and substances (2)
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Note on elementary and compound substances
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Stuff
& Substance uses the terms ‘elementary
substances’ and ‘compound
substances’ instead of the more usual
‘elements’ and ‘compounds’.
This is part of a deliberate and permeating focus on
the idea of a substance, and is intended to avoid the
ambiguity referred to in the Language alert below. In
this approach there are just atoms
and substances.
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Students need to
be aware that careful tests need to be done to find
out whether a substance is an elementary substance or
a compound substance, and it is not possible to decide
whether a substance is one or the other just by looking
at the sample on the macroscopic scale.
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Notes on Language alert
People often say ‘water is
made of oxygen and hydrogen’, meaning it is made from
oxygen atoms and hydrogen atoms. The substances
oxygen and hydrogen are not there: the only substance is water.
It is important to ensure that students understand that the
properties of water are not some strange mix of the properties
of oxygen and hydrogen: the substances oxygen
and hydrogen are not present in water and the phrase
‘the individual atoms do not have the properties’
applies to compounds, not just to elements.
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Science Enhancement Programme CD-ROM 2005 |
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user
guide |
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