|
|
 |
|
|
TGM8:
Reaction in solution
|
|
 |
LINKS |
 |
|
|
|
|
Notes on the video of lead nitrate and potassium iodide
A yellow ‘cloud’ forms as the solutions are mixed:
this is a new substance in the solid state, which has a very
low solubility. Students should realise that filtering
should separate the yellow powder from the mixture, and that
allowing the filtrate to evaporate will tell us whether it
was just water or if it contained other, dissolved, substances.
The potassium nitrate has a slight yellow tinge because some
traces of lead iodide are present: filtering removes undissolved
lead iodide, but some dissolves and so passes
through the filter paper; it is not possible to tell just
by looking at the sample, but the lead iodide will also have
a small amount of potassium nitrate mixed in: this would have
been in the wet residue in the filter paper and would also
have been left as the water evaporated.
‘Think for Yourself’ question
All of the substances stay in the solid state at high temperatures.
What kind of structures are they likely to have?
Giant structures.
Note on concept of a precipitate
Students need to understand that if the solubility of lead
iodide were high, there wouldn’t be a precipitate to
see.
Notes on the video of carbon dioxide and calcium hydroxide
solution
Students should be able to suggest that the calcium carbonate
could be removed by filtering.
|
|
|
|
|
| a
Science Enhancement Programme CD-ROM 2005 |
|
user
guide |
| |
|
|
|
|
