Hidden Chemistry Leader’s Notes – Higher (2 hr session)
This 2 hour session is split into 3 parts. It does not matter how much of each section
is completed, the emphasis is on pupils trying something new, testing and evaluating,
and having fun! The experiments are all ‘supermarket chemistry’ and so the associated
hazards are not too high (see risk assessment). Again the emphasis is on
experimenting and thinking critically in order to draw conclusions.
THE INVESTIGATION (30 minutes)
The aim of this part of the session is to get the class to read the cards about items with
hidden chemistry in. they are given a set of clues and a set of questions. They use the
clues to identify the item and then answer some short comprehension question about
each. Encourage the class to work in groups as there are likely to be too many items
for any one person to complete in 30 minutes. This can then be used to encourage
collaboration between peers as one group tries to get all the items. There is space in
the booklet to fill in the identities of each item and the answers to the questions.
During the session please circulate and keep individuals on point, help out where
necessary but try to avoid giving pupils the answers. An answer scheme is not
provided for this reason.
Please read the following instructions aloud to the class: “On each table there are 12
cards describing 12 items with hidden chemistry. Working in teams you need to
read the clues for each item, identify the correct item, read the card for the item
then answer the questions about it. You have 30 minutes to do this. You will be
able to work faster if you split your teams up to work on more than one item at
once. Can you identify all 12 items?”
THE LAB (45 minutes)
There are 3 different experiments. Pupils should work in pairs or small groups and
follow the instructions in their booklets. Set up an experiment station (approx. 10 pupils
per station) in 3 locations around the room. Pupils will have 15 minutes at each station
then rotate, such that everyone has a go at each experiment. There are photographic
instructions with each experiment.
Please read the following instructions aloud to the class: “There are 3 different
experiments to try in the room. You will spend 15 minutes at each experiment
station. Please follow the instructions on how to conduct each experiment in
your booklets and with each experiment. As this is a research lab session you
must behave in a safe manner. Do not put anything in your mouth and try to
work tidily. Record what you see as you do each experiment in your booklets. I
will tell you when it is time to move to the next station.”
a) Making emulsions (making mayonnaise) – CAUTION: RAW EGG
The pupil will pour some cooking oil into a plastic cup, up to 1 cm deep. They will then
pour some water into the same cup, up to 1 cm deep again. The water should sink
below the oil, when stirred gently with a spoon the layers may mix a little but will
separate out when left. The pupil will then add one of the agents listed in their booklets
(sugar, flour, mustard powder, egg white and egg yolk). They should see that some of
these agents stop the mixture from separating after being stirred (may need to be
stirred quite well). It doesn’t matter if students want to add 2 or more agents at once,
so long as they don’t consume any egg. They can make notes about their observations
in their booklets.
b) Fruit batteries
The pupil will push a penny and a galvanised nail about ½ way into any of the pieces
of fruit. They will then clip one end of a crocodile clip to each and the other end to each
leg of an LED (CAUTION: SHARP ENDS). This should light the LED up (if this doesn’t
work try swapping the connection on the LED round). The pupils can then try a different
piece of fruit, or connect a series together. If a multimetre is available the pupils can
quantify which makes the best fruit battery, if not it can be observed qualitatively by
how bright the LED shines.
c) Soap and surfactants (milk art)
The pupils will pour a small amount of milk into one of the dishes. They will then add
one drop of a food colouring gently to the surface of the liquid with a pipette (this is
quite fiddly so encourage the pupil to take it slowly). Then the pupil will dip a cotton
bud into some washing up liquid or liquid soap and touch the spot of food colouring
with it. The food colouring should race away from the detergent and form a ring. The
pupil can then add more spots of food colouring. When they have added all the food
colouring they want they can gently lay a piece of filter paper on top of the dish,
touching the surface of the milk. When lifted away this should have a transfer of the
food colouring on it. Different pupils at the station should be encouraged to use
different detergents to see if the effects are different.
At the end of the session make sure that the pupils put everything into the trays
and wash their hands.
THE REFLECTION (30 minutes)
The pupils have been asked to make a visual display of their favourite part of the
session. They are also asked to ‘interview a scientist’. This section has been left
deliberately open to allow each pupil to reflect on the session as they want to. The
interview is certainly not compulsory for those that may struggle with it. This section
can be cut shorter or run longer to allow for a timely finish.
Please read the following instructions aloud to the class: “Now we would like to know
what you thought about today. Make a poster about your favourite part of the
workshop. It can be one of the items you learned about, one of the experiments
you conducted, or anything else you have enjoyed. If you would like to you can
also interview one of the scientists in the room today, to find out more about
what they do and how they got there.”