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TGW7:
Looking for patterns
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‘Looking
for patterns’ pulls all the reactions of acids together
with the underlying concept of the need for the acid and the
product of the reaction (other than hydrogen or carbon dioxide)
to dissolve in water.
Notes on the ‘three reactions’ image
Students should be able to identify a pattern of the hydrogen
atoms in the acid molecules being replaced by a ‘metal’
atom. The next page gives a full summary for the three acids.
Notes on the ‘Think for Yourself’ questions
How can you tell that not all the acid was used up by the
lumps of calcium carbonate?
When the magnesium strip is dropped
in, there is lots of fizzing and no magnesium strip is left.
Why did the fizzing stop when there were still lumps of calcium
carbonate left if there was still plenty of acid to react
with?
The reaction between sulfuric acid
and calcium carbonate produces calcium sulfate. Calcium sulfate
has a very low solubility and does not dissolve in the water
as it forms, so each lump becomes coated with a layer of calcium
sulfate. Although there is plenty of acid left, it can not
get to the calcium carbonate.
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Science Enhancement Programme CD-ROM 2005 |
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user
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