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TGL3:
More about molecules and structures
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Notes on melting point and molecular structure
For a substance with small molecules, water
has higher melting and boiling points than expected. All other
substances with just three atoms per molecule have boiling
points well below room temperature. For special reasons, the
hold between water molecules is quite strong (but still nowhere
near as strong as a bond between atoms).
The shapes of molecules
Students may have noticed that the water and carbon dioxide
molecules are both made of three atoms but they
have different shapes. Again, this is due to the type of bonding
- there are only certain positions where bonds can
form – but this is not something we consider in this
topic: at this stage students should simply know that there
are different kinds of bond and that different
molecules do have different shapes.
Notes on ‘complex giant structures’
Students will be able to predict when this kind of structure
will form when we learn more about acids later on. For now,
it is enough to appreciate that this kind of arrangement is
possible.
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Science Enhancement Programme CD-ROM 2005 |
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