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TGV10:
Decomposition or combustion
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LINKS |
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Notes
on the decomposition of sugar
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The giant structure
of carbon atoms is the black stuff – it is a charcoal.
It forms so quickly that there are no
proper crystals. |
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The other substances
all escape in the gas state. This mixture of substances
makes up the bubbles. They are not
sugar in the gas state! |
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The methanol, carbon monoxide,
methane and hydrogen will all react with the oxygen
in the air to give a flame. |
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Although it is very hot, no
air can get to the carbon in the tube. |
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The yellowing we saw when the
sugar first melted was a sign that some of the
sample was hot enough to
decompose. |
Notes on the video of decomposition of wood
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There are signs
of a colour change early in the video, evidence that
wood is decomposing just as sugar did, forming a complex
mixture of new molecules: the ‘smoke’ in
the upper part of the tube is where some of the new
substances are condensing. Droplets can also be seen
on the sides. |
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Some of the substances
react with oxygen: if asked, students should be able
to suggest that these substances might include methane,
hydrogen and carbon monoxide ( as in the decomposition
of sugar). |
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Pause before going on to the
section where one of the lumps of charcoal is heated
in oxygen and ask students to predict what might happen.
Draw students’ attention to the ash and ask what
this tells us about the purity of the lump of charcoal
– is it just carbon?(Note: the absence of a residue
would not prove the lump is pure carbon). |
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Science Enhancement Programme CD-ROM 2005 |
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user
guide |
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