Re: What are "principles" in science?

[John Denker <jsd@AV8N.COM>]

Ludwik Kowalski wrote:
> After elaborating on what (a) experimental facts,
> (b) hypotheses, c) theories and (d) laws are in
> science an author of a textbook inserted:
>
> "A  PRINCIPLE TO REMEMBER. In a chemical
> change the atoms in substances are rearranged
> to make one or more new substances. The result
> is a change in composition."
>
> Would it be appropriate to replace the word
> PRINCIPLE by the word LAW?

There are several questions on the table.

1) We can agree that the alleged principle needs repair.

2) Replacing principle --> law is permissible, but doesn't
solve the main problems.

Scientists use a number of words such as law, principle,
rule, etc. almost interchangeably.  Of course there are
connotations and nuances, but they are rarely if ever
important.

3) The alleged principle is so messed up that one hardly
knows where to begin criticizing it.
 *) Do the two sentences express two principles or just one?
 *) Is it trying to define the notion of "chemical change"?
  -- If that is the same as a chemical reaction, why
     introduce nonstandard terminology?
  -- If that is not the same, the distinction needs to be
     clearly explained.
 *) For example, what about an allotropic change such as
    tin pest?  There is a rearrangement of atoms, but no
    real change in composition.
 *) For a different example, suppose I mix oil and lemon
    juice and egg-yolk to make mayonnaise.  There is
    rearrangement of atoms and a change in composition,
    but does it really count as a _chemical_ change?

One should also keep in mind the law/rule/principle of
pedagogy that learning proceeds from the known to the
unknown.  The alleged principle doesn't do much good
unless the students already have a decent understanding
of "substance" and "composition" et cetera.