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TGV5:
More flames: oleic acid.
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LINKS |
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Notes
on the video of oleic acid burning
You will probably find it useful to go back over the ignition
frame by frame.
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Students should notice that
the oleic acid in the watch glass does not ignite. They
should be able to suggest that this is because there
are not enough oleic acid molecules mixed in with the
oxygen molecules, because oleic acid evaporates slowly. |
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When the oleic
acid is boiling, students should be asked what the bubbles
are, and should be able to identify these as oleic acid
in the gas state. Remind students that the observable
mist is not oleic acid in the gas state. (However, amongst
the droplets of mist there will be single molecules
of oleic acid mixed in the air). |
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Ask students to
suggest why the heated oleic acid ignites: they should
be able to suggest that heating so that the oleic acid
boils has ensured that there is a mixture of oleic acid
molecules and oxygen molecules. |
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You might like to point out
that the oxygen atoms in the oleic acid molecules are
not responsible for the reaction. |
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As you show the
section ‘Can a glass wick help?’, pause
and ask students, ‘What is the wick doing?’,
‘What must happen before the oleic acid ignites?’
and ‘What new substances will be formed?’
(The answers can all be checked by using the summary
diagram on page V3.7). |
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Some students may
also note that the flame is ‘dirty’ or ‘sooty’:
this is dealt with in ‘Incomplete combustion’
on page V5.4. |
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Science Enhancement Programme CD-ROM 2005 |
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user
guide |
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