Hands-on experiments

Alyson Tobin at6 at st-andrews.ac.uk
Wed Mar 18 12:50:00 EST 1998


I asked for suggestions for experiments for a one day exhibition for
families and got a number of helpful comments. The open day was on saturday
and it was a great success. Thanks to everyone who offered suggestions.
Here are some of the things that worked well:

Wild oat seeds: show an impressive response to water. Spray with a
water/mist spray and watch them- within seconds the awn on the seed rotates
and the seeds wriggle and twist.

Red cabbage dye: grind a red cabbage in about a litre of water and filter.
This produces a rich, red solution of anthocyanins that show pH-related
colour change. I presented the children with a range of different household
chemicals- lemon juice, baking powder, soap, Irn Bru (Scottish equivalent
of Coca Cola and quite acidic!) etc. and the dye produced a range of
colours from vivd red/pink (acid) through greens, blues and purples
(alkaline).

DNA extraction from onion. Grind an onion in a food blender for 5-10
seconds in 10ml washing up liquid (cheap, weak ones work best) plus 100 ml
water and 3 gm salt. Filter and put into a test tube- half full. Then fill
to the top with alcohol (clear methylated spirits) and turn the tube over
and over a few times. The DNA 'appears' as a white, slimey substance and it
will float to the surface of the ethanol where it can be removed on a
plastic stick. The whole process takes about 2 minutes and was very popular
with kids and grown-ups. All 5 year olds know what DNA is after Jurassic
Park!

Colouring flowers: simple and eye catching. Put cut flowers into food
colourings and within minutes if lights are bright the colours change-
shows water uptake and also attracts their attention. White carnations
worked well as did daffodils, which looked dramatic in red colouring,
taking on the appearance of blood running through the veins.

Make a wind-transported seed: simply cut a strip of papers, fold and twist
through the middle, add a paper clip and this is a basic design of a
sycamore seed. We ran a competition to see how long the 'seeds' took to hit
the floor when dropped from the ceiling- the ones remaining in the air for
longest won the prize, as these would be transported furthest  on the wind.

Starch prints: Took a lot of preparation. I put bean plants in the dark for
48 hours then taped a black and white negative of cartoon characters onto
leaves, put the plants into continual light for 48 hours, put the leaves
into boiling ethanol and then stored them in damp tissue until the day- if
they dried out they shrank and were useless. On the day the children just
had to add iodine solution and watched the character appear on the leaf-
worked extremely well.

Planting cress seeds on cotton wool in paper cups- the children drew faces
on the cups and the cress will grow into 'hair'.

The trick on the day seemed to be to have something 'eye-catching' that
brought the families to the table. This was a science event and we were
'competing' for their attention with exhibitions on volcanoes, 'how the
brain works' electron gadgets etc. The demos also had to be quick- as
instananeous as possible- and the colourful ones were popular.

It was a very enjoyable day and we got a lot of interest and enthusiasm
from a wide age-range. I hope this encourages others to have a go!

Thanks again for the suggestions.

Alyson Tobin


Dr A.K. Tobin
Plant Science Laboratory
School of Environmental and Evolutionary Biology
Sir Harold Mitchell Building
University of St Andrews
St Andrews
KY16 9TH
UK

Tel 01334 463375
Fax 01334 463366





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