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TGSU4:
Addressing the issues (2)
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Substances
in the gas state
Stuff & Substance introduces
the basic particle model in the context of explaining melting
and then uses it to consider the gas state, which many students
find difficult to understand. The practical aspect to this
is the use of plastic bags to show the consumption and emergence
of substances in the gas state in the videos of chemical reactions.
Evaporation and boiling
Research has shown that students find it difficult to reconcile
the concepts of evaporation at room temperature and of boiling,
so Stuff & Substance
introduces the idea of high, medium and low energy particles
within a sample at a particular temperature. Extended in this
way, the basic particle model can be used to explain a whole
range of phenomena involving changes of state and/or mixing
and separation.
Chemical change and chemical structures
Each substance is defined by the bonded atoms that make up
its ‘particles’. A rearrangement of bonded atoms
would give new particles and hence new substances. Stuff
& Substance presents a sequence of examples of
chemical change of increasing complexity that culminates in
a lighted candle with a string wick.
Although research indicates that students take to molecular
structures more easily than giant structures, the approach
is to cover both and introduce the two together. The rationale
is that an encompassing and coherent model is easier to learn
than a limited and fragmented one. The idea of two types of
structure can grow out of the basic particle model without
contradiction: for molecular structures, the hold between
the particles is weaker than the bonds between atoms inside;
for giant structures, the hold between particles is of the
same nature and strength as the bonds between atoms inside.
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Science Enhancement Programme CD-ROM 2005 |
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user
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