• To devise and carry out experiments to test simple
• To develop the idea of the ‘fair test’.
One lesson of approximately one hour. Some of the planning
could be done for homework.
A discussion of why salt is added to water when cooking
vegetables leads on to open-ended investigations devised
by the students to discover (a) whether this salt can be
detected in cooked beans and (b) what level of salt can
be detected by taste.
The lesson could be started by introducing Heston Blumenthal
as a ‘scientific chef’ and showing the video
clip of him discussing the use of salt in cooking food and/or
by discussing some of the issues listed below at a level
appropriate for the students concerned.
/ wmv(15) / MPEG
Heston Blumenthal in
One question posed by Heston Blumenthal early
in his career as a ‘scientific chef’ was
'Why do cooks add salt (sodium chloride) when cooking vegetables,
for example green beans?’ Possible reasons
suggested by cooks included:
A scientist colleague replied that there seemed
to be no good reason because:
acidity and calcium content of the water affect the
colour of the beans
adding salt does
increase the boiling point of water but by such a
small amount that it will make no difference to cooking
vegetables will go
soggy if cooked for too long whether salt is added
very little salt is
actually absorbed onto the surface of a bean during
cooking – typically 1/10 000 g of salt per bean
which is too little to be tasted by most people.
Students can try to test some of these suggestions
and explanations by experiment
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