Accidental discoveries

Accidental discoveries
Accidental
discoveries
Part of the British Science
Association’s British Science
Week activity pack series.
www.britishscienceweek.org
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Accidental discoveries: Bakelite plastic
Making silly putty
More than one hundred years ago, electric wires were covered with ‘shellac’.
It stopped people getting an electric shock if they touched the wire. It was
very expensive because it was made from beetles that came from
Asia. So, a man called Leo Baekeland decided to make a new
type of covering. However, instead he discovered how to
make the first plastic, called Bakelite. Plastics
can be moulded into all kinds of shapes.
They are used to make all sorts of
things. You can have a go at making
a bouncy plastic, called silly putty.
You will need: 2 containers (such
as plastic cups), a wooden stick (for
stirring), some food colouring, PVA
glue, borax solution (about 1 tablespoon
of borax to a cup of water)
This 1950s telephone is made from Bakelite
What you do
Put about one tablespoon of borax into one cup of water. Stir until it dissolves. Stir in two or
three drops of food colouring.
Put some PVA glue into the other container – just enough to cover the bottom.
Pour some of the borax solution into the PVA glue. Stir the mixture until it makes a soft lump.
By now the mixture should be joining together like putty. Take it out of the container and
mould it into a ball in your hands. If it is still sticky, wash your hands with water and rinse the
ball. You have made silly putty!
Try squishing it into different shapes. Does it bounce?
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Accidental discoveries: Artificial sweeteners
Light sweeteners
One day in 1879 a man called Constantin Fahlberg
was trying to discover new uses for coal tar (a sticky
black substance used for making paints and other
useful things). At lunchtime he sat down to eat a
sandwich – without washing his hands. His bread
tasted very sweet.
At first he couldn’t understand why.
So, when he went back to work he tasted some of
the chemicals he’d been working with. One of them
was very sweet. It was called ‘saccharin’. It can be
used instead of sugar to make things sweet.
You will need: a large container of water, a 330ml
can of fizzy drink, a 330ml can of diet fizzy drink
(make sure they’re the same brand, so there are less
‘variables’ – other things stay the same).
What you do
Place the can of regular fizzy drink into the container
of water. What happens?
Now put the can of diet fizzy drink into the water.
What happens?
Artifical sweeteners are
used in ‘diet’ fizzy drinks
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Accidental discoveries: Play-Doh®
Play-doh® circuits
In the 1930s a company called Krogers Grocery made
a product to clean coal from wallpaper. Then, one of
the workers saw some school children using it to make
Christmas decorations. So, he added some colour and sold
the product as a toy for children. It was called Play-Doh®
and is still popular today. You’re going to make your own
Play-Doh® and use it to make an electric circuit.
You will need: a mixing bowl, 200ml water, 100ml salt, food
colouring and plastic gloves, 100ml cream of tartar, a
tablespoon, vegetable oil, 400ml plain flour (plus a bit extra
for sprinkling on the tray), a wooden spoon, a board or tray,
a battery pack, leads, an LED or light bulb in a holder.
What you do
Put on your plastic gloves. Pour 200ml water into a mixing
bowl. Add the salt and a few drops of the food colouring.
Stir. Add 100ml cream of tartar, a tablespoon of vegetable
oil and 400ml flour. Stir until it is mushy (not watery or floury).
Sprinkle the board or tray with flour. Scrape the mixture out
of the bowl onto the board or tray. Knead it with your hands
until it turns into a ball. If it still feels sticky add a bit more flour.
If it is too stiff, add a few drops of water and knead again.
Add flour or water until you have a nice soft but not sticky
ball. Now use your play-doh to connect leads to make a
simple electric circuit to light your LED – like in the picture.
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Play-Doh®
A simple play-doh circuit
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Accidental discoveries: Chocolate chip cookies
Melting chocolate
Nearly one hundred years ago, a lady called Ruth Wakefield
was making cookies when she ran out of cooking chocolate.
Cooking chocolate melts and makes the cookies all brown and
chocolatey.
She didn’t give up and used a different type of chocolate
instead, called ‘semi-sweet’ chocolate. But it didn’t melt.
Mrs Wakefield had accidentally invented the chocolate
chip cookie!
She sold the recipe to Nestlé in exchange for a lifetime
supply of chocolate chips.
You will need: different types of chocolate samples
(such as milk chocolate, chocolate chips, cooking
chocolate, dark chocolate), a cup and saucer, hot
water at about 45 OC (water from the hot tap should be
OK), a timer.
What you do
Mmm, chocolate chip cookies!
Carefully pour the hot water into a cup so it’s nearly full. Place
the saucer on top.
Wait for a few minutes until the saucer gets hot.
Break the different types of chocolate into same-sized pieces.
Place a piece of each type of chocolate on the saucer. Start the timer.
How long does it take for each kind of chocolate to melt?
Which chocolate would you put into a cookie?
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Accidental discoveries: Microwave oven
The speed of light
Percy Spencer was an engineer. One day at work
he was stood next to a bit of machinery called a
magnetron. It made microwave radio signals. He
noticed that a bar of chocolate in his pocket melted.
Percy had accidentally discovered that these signals
could make things hot. He used his ideas to make
the first ever microwave oven. You’re going to use
chocolate buttons and a microwave oven to measure the
speed of light.
A microwave oven
You will need: a microwave oven, a microwavable plate, some chocolate buttons (enough to
cover the plate), a ruler and a calculator.
What you do
Sprinkle the chocolate buttons so they cover the plate. Take the turntable out of the
microwave oven. Put the plate and chocolate in. Set the microwave oven to full power and
start cooking the chocolate. Watch it very carefully. As soon as it starts to melt (usually about
20 seconds) stop the oven. Let the plate cool for a few minutes, then take it out.
There should be melted spots in the chocolate. This is where the microwave energy has been
highest.
Now you have to do some tricky maths – so make sure you have a calculator. You might
need to ask your teacher for some help. Measure the distance, in centimetres, between
the melted spots. Add all your measurements and then divide the answer by the number of
measurements you took – that is the average distance.
Times the average distance by two. Divide this number by 100 (to get the distance in metres).
Then multiply by 2450 000 000. The answer is the speed of light in metres per second.
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Accidental discoveries: Pacemaker
Rhythm of the heart
Sometimes, if somebody’s heart doesn’t beat quite right, they have
a ‘pacemaker’ fitted. It helps to keep their heart beating at just the
right rhythm.
The pacemaker was an accidental invention. An engineer called
Wilson Greatbatch was building something to record the rhythm of
people’s heart beats. He reached into his tool box and accidentally
pulled out the wrong bit of kit. He fixed it to his circuit. The circuit
‘pulsed’ for 1.8 milliseconds and then stopped for one second. As
luck would have it, that was just the right rhythm needed to make a
pacemaker.
You will need: a partner, a wrist heart monitor or timer, a calculator.
A pacemaker
Radial artery
What you do
Sit down and keep calm while you read these instructions.
When your partner is feeling relaxed, follow the instructions which
come with a wrist heart monitor to find their resting heart rate.
If you don’t have a heart monitor, you need to find the pulse at their
wrist: ask them to rest their arm on a table or desk with the palm up.
Use the tips of your first two fingers to find their pulse about 2 cm
below the base of their thumb. Have a look at the picture to help.
Count the number of beats in 15 seconds. Multiply by four to get the
number of beats per minute.
How many beats is this per second?
How does this compare with Wilson’s circuit?
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Accidental discoveries: Radioactivity
Detecting radiation
More than a hundred years ago, a man called Henri Becquerel
decided to do some experiments. He wanted to see if things
that glow in the dark could produce X-rays if they were left in the
sun. (There was probably a very clever reason for this!)
But when he decided to do his work, it was winter. There wasn’t
much sun. So, he put his materials in a drawer and waited for a
sunny day. When he took them our he noticed that a rock had
made an image on a piece of paper. The rock was radioactive.
You can’t investigate radioactivity (it’s really dangerous!). But
you can make cool pictures with objects using something called
sunprint paper – a bit like when Henri left his rock in a drawer!
You will need: a sunny day, a piece of sunprint paper in an
Henri Becquerel
envelope, a sink with cold water tap, a stopwatch, some objects
for your picture (you can choose pretty much anything as long
as they will stay on the paper – leaves, feathers, pens, scissors, cut-out shapes).
What you do
Choose your objects. Decide how you want to arrange them to make a picture or pattern.
Take the sunprint paper out of the envelope.
Quickly place the objects on it and put it in a sunny place for two minutes.
Quickly take off the objects.
Put the sunprint paper back in the envelope and take it to a sink.
Take out the sunprint paper and rinse it. Hang it up to dry.
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Accidental discoveries: Penicillin
Growing mould
In 1928, Alexander Fleming was growing bacteria in Petri dishes.
Bacteria are tiny living things – some of them make people
poorly. One of the dishes accidentally got some mould
in it. He noticed that the bacteria didn’t grow close to
the mould. The mould is now used as a medicine, called
‘penicillin’. It can kill bacteria. You may have taken some, if
you’ve ever been poorly with an infection.
You can’t actually make penicillin yourself, but you can
investigate the growth of bacteria and moulds in Petri dishes.
You will need: a fine (thin) permanent marker pen, a sterile Petri
dish with clear jelly containing nutrients (food), a clock or timer,
some clear sticky tape.
Mould growing
on a Petri dish
What you do
Handle the Petri dish carefully – it has a loose lid that must stay on until you start your
experiment.
Use the marker pen to write your name on the base. Place the dish where you want to test the
air for bacteria and mould spores (tiny structures that can grow into new moulds).
Remove the lid completely. Do not lean over the dish or breathe on it. Replace the lid after
fifteen minutes. Stick the lid on with four pieces of clear tape placed crossways
– do not seal all round the edge (look at the picture).
Leave it in a warm place until you can see some changes. Look for hairy
structures growing on the jelly.
Can you see any clear areas around the hairy structures?
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Accidental discoveries: Vulcanised rubber
Treating rubber bands
Have you ever heard of ‘vulcanised rubber’? Probably not! But it’s
used in all sorts of things such as car tyres and shoes. It was discovered
accidentally, when Charles Goodyear spilt a mixture of rubber, lead and
sulfur (a chemical) on to a hot stove. The mixture burnt a bit. It then went
hard but was still usable.
You will need: untreated rubber bands, rubber bands that have
been treated in different ways (stored in water, oil or alcohol, or
left in sunlight, heated or frozen), some weights and hangers, a
ruler, a pencil.
What you do
You will need to work with at least one other person.
Loop one of the rubber bands around a pencil. Hang a weight
hanger from the rubber band.
Tyres made from
vulcanised rubber
Measure its ‘original length’ to the nearest millimetre – record the
result in a table, a bit like the one below. Add weights until the rubber band has
stretched to three times its original length. Compare the rubber bands
treated in different ways.
treated
untreated
water
oil
sunlight
heated
frozen
original length (mm)
number of weights
needed to stretch
rubber band to threetimes its original length
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Accidental discoveries: Smart dust
Making a mote
Silicon chips are used in computers and other electronic devices.
A student, called Jamie Link, was working with silicon chips
when one burst into pieces. She then discovered that the
tiny pieces could still work as ‘sensors’ to detect changes in
all kinds of things. It is now possible to put tiny devices called
motes in different places to warn about changes. One of
the things they are used for is detecting how much salt is in
concrete. It’s helpful because salt can weaken concrete – and
no-one wants bridges to start falling down!
You can’t use motes in the classroom (they’re too small!) but you
can have a go at making a sensor for
detecting salt.
You will need: a plastic cup, water,
some salt solution, a battery pack,
leads, an LED or light bulb in a holder.
What you do
Set up an electric circuit like the one
in the picture.
Carefully pour salt solution into the
water until the bulb lights up.
cup of water
(about half full)
leads (make sure
they touch the water,
but not each other)
bulb in holder
battery in battery holder
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Accidental discoveries: Coca-Cola®
Adding the fizz
John Pemberton was trying to make a cure for
headaches when he invented Coca-Cola®.
For eight years it was only sold in chemist shops. But it
became so popular that it was put in bottles and made
available everywhere. It eventually became the best
selling fizzy drink in the world.
The recipe is still a closely guarded secret, but you can
make your own fizzy drink.
You will need: a place where food can be prepared,
a lemon, a clean knife, a clean plastic cup, drinking
water, a teaspoon, sodium bicarbonate, sugar.
Squeeeeeze!
What you do
Cut the lemon in half and squeeze as much of the juice
as you can into the cup.
Add an equal amount of water to the lemon juice.
Add a teaspoon of sodium bicarbonate.
Taste your drink and add some sugar if you think it needs
to be sweeter.
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Accidental discoveries: Teflon®
Introduction
In 1938, a man called Roy Plunkett was doing some work in his
laboratory. He was using gases to try to make a ‘coolant’ (a
liquid that helps make refrigerators cold). One of his attempts
went wrong and he accidentally discovered a slippery
powder, called Teflon®.
Teflon® is so slippery that pretty much nothing sticks to it. It’s
used to coat non-stick frying pans. It’s also used to make
tape, which plumbers use to make water-tight seals on pipes.
You will need: a permanent fine marker pen, some Teflon® tape.
What you do
Write your name on a piece of Teflon® tape using a marker pen.
Carefully stretch it sideways in a few places to mess up your writing.
Now take the ends of the tape and pull it lengthways.
What happens to the tape and the writing?
A frying pan
coated with Teflon
Plumbers’ tape
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Accidental discoveries: Mauve
Extracting dyes
Way back in 1856, an 18-year old chemist was trying to
find a cure for malaria (a really deadly disease which kills
millions of people). But his experiment went a bit wrong.
He looked at what he’d made and, even though it wasn’t
what he’d hoped for, he thought it looked rather nice. He
had accidentally made the first ever synthetic dye – he
called it Mauve. It was nice and bright and didn’t fade.
Dyes are used to make clothes and other fabrics colourful.
It’s a bit tricky to make synthetic dyes in your school (the
chemicals you need must be used very carefully). But you
can make natural dyes from foods and plants.
Group activity
This activity is
great for group
work – you
could all make a
different dye.
You will need: a kettle and water, glass jars, various plants
and foods to extract dyes from (such as beetroot, coffee
beans, carrots, mint leaves, dandelions, red onion, tea leaves), a knife, a pestle and mortar, a
sieve, some pieces of white fabric to dye (an old cotton t-shirt or sheet, for example).
What you do
Decide which foods and plants you want to make natural dyes from. Then, for each one:
Chop it up (or crush it in a pestle and mortar if you can’t cut it). You might even be able to use
an electric food chopper if your teacher has one. Put a small handful of it to a glass jar. Nearly
fill the jar with boiling water from the kettle [be careful!]. Leave it for about 10 minutes to cool
down. Pour it through a sieve into a clean jar, to get rid of the bits. You now have a natural dye.
Use it to dye some pieces of fabric. Cut your fabrics into same-sized squares (about 5 cm x
5 cm should be OK). Add a bit of fabric to the jar of dye and leave it for a few minutes. Take it
out of the jar and hang it up to dry.
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Accidental discoveries: Tea and tea bags
All the tea in China
According to ancient Chinese legend, tea was invented accidentally nearly
5000 years ago! A Chinese Emperor called Shen Nong liked to boil water
before drinking it (he thought it was more hygienic). Then, one day when his
servants were boiling up some water, the leaves from a camellia bush fell in.
The emperor thought it smelt lovely. He took a sip and it tasted lovely too!
These days we make our brew using a tea bag.
H Have you ever helped to make a cup of tea?
H Do you know how tea bags work?
Your challenge
Find the best material to make a tea bag. Do you think it will be kitchen roll?
Maybe newspaper could work. What about a thin fabric?
Here’s one way to find out
Cut out a square of kitchen roll. Put a teaspoonful of tea leaves in the
middle. Gather up the corners with a clothes peg to make a bag.
Half fill a clear beaker with water from the hot tap. Holding the peg,
dunk the tea bag up and down in the water for one minute.
Try other papers and fabrics to see which type makes the best tea
bag (lets the flavour and colour out, and keeps the tea leaves in).
Take care with the hot water and don’t drink the tea!
H Can you think of other ways to test tea bags?
some extra things to do
Talk about
Talk to your friends
about your ideas.
Plan how you
can test different
tea bags with a
buddy. How will
you know which is
the best tea bag?
share your ideas
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Accidental discoveries: Velcro® (learning from plants)
Learning from plants
In the 1940s a Swiss engineer was out walking his dog. When he got home he
realised that he and his dog were both covered in ‘burrs’ (a type of seed sack
from plants). He looked at one under a microscope and saw it
had lots of little hooks – that’s why it hooked onto his jumper.
He used this principle to make a new fastening device, which
he called Velcro®. These days it’s really common. It just goes
to show that looking at plants is really useful!
Your challenge involves making and testing models that fall
to the ground like seeds from a sycamore tree.
H Have you ever seen a sycamore seed fall to the ground?
H Do you know how to make a model sycamore seed?
Your challenge
Find out whether the size of the ‘blades’ make a difference to
the speed at which your sycamore seed falls to the ground.
Here are some ideas to get you started
Make sycamore seed models like the diagram. Put a paper clip on
the bottom to help them fall properly. What sizes will you make them?
How big will you make the blades? How many clips will you add?
Now put them to the test
Watch the seeds carefully as they fall. Can you make them go faster
and slower? You could try landing them on a target and score points
for where they land. Remember to change only one thing at a time.
some extra things to do
A model
sycamore
seed
Talk about
What happens if
you drop flat and
scrunched up
paper? What do
you notice about
the way that they
fall? What might
be making a
difference to the
way that they fall?
share your ideas
A ‘burr’ from
a burdock
(a type of
thistle)
A real
sycamore
seed
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Accidental discoveries: Organiser’s notes
Accidental discoveries
For each activity, read through the
pupil instructions to familiarise yourself
with the method. Make sure the pupils
understand what they are going to do.
Check the ‘what you need’ list and
make sure that everything that pupils
need is available. Extra materials may be
needed for trial runs or repeats.
Give pupils all the equipment they need
and make them aware of any health
and safety issues; a risk assessment
should always be carried out before
starting any practical work.
Read through the notes below for some
additional information for each activity.
Bakelite Plastic
Equipment and advice: You can
buy borax in some supermarkets and
hardware stores (don’t get the stuff
called Natural Borax Substitute!). Plenty
of places sell it online, too: search on
Amazon (Fizzy Cosmetics is good).
A saturated solution of borax is needed.
It can take a while to dissolve, so you
might want to do this for the pupils.
Background science: Borax solution
causes the polymer chains of polyvinyl
acetate (PVA) to cross-link. PVA chains
normally move easily and form a liquid.
When the chains become cross-linked
they can no longer slide easily and form
a solid but flexible plastic material.
Additional health and safety note: Borax
can be harmful if swallowed and is an
irritant. Wash your hands after touching
the putty. Do not taste or ingest putty.
Wear eye protection and an apron or
laboratory coat for this preparation.
Artificial sweetener
Equipment and advice: You’ll need quite
a large container of water for this – a fish
tank is good because pupils can look
through the sides.
Background science: Although the
two cans of fizzy drink have the same
volume, they have different densities –
it’s because of what’s dissolved in the
drink. Diet drinks use artificial sweeteners.
Regular drinks use sugar. Artificial
sweeteners are sweeter than sugar. So,
you need about 40 grams of sugar but
only a few grams of artificial sweetener.
The difference in the amount of dissolved
sweeteners is what causes a difference
in density.
Play-Doh®
Equipment and advice: Plastic cups can
be used. If the facilities are available, the
mixture can be gently heated on a very
low heat in a saucepan before kneading
(a risk assessment should be completed
and appropriate safety measures taken).
The mixture should be stirred until it forms
a ball. Make sure an adult checks that
the ball is not too hot before kneading.
Do not allow the mixture to be eaten.
The instructions provided make a pretty
big ball of play-doh! ... it might be best if
pupils work in small groups, or you could
reduce the quantities.
Components for the circuits can be
bought online or from shops such as
Maplins. Don’t connect the batteries
directly to the LEDs – it can cause them
to get hot and burn out; the play-doh
should provide enough resistance to
prevent this.
Background science: The salt water in
the play-doh is a conductor, so it will
allow an electric current to flow.
Chocolate chip cookies
Equipment and advice: If pupils have
access to a food preparation area, they
could experiment by making cookies
themselves, using different types of
chocolate.
Background science: This useful website,
www.food-info.net, says “The type of
chocolate and its ingredients will have
an effect on the heat resistance and
melting of the finished product. Melting is
important for the mouthfeel and taste of
the chocolate.”
Microwave oven
Equipment and advice: Pupils should not
be allowed to use the microwave oven
unsupervised – an adult should take the
plate out of the oven as some plates get
very hot. Microwave frequency varies
slightly between ovens, the exact figure
may be found on the oven.
Note: sometimes, even with the
microwave plate removed, the plate
of choclate touches the rotating
mechanism and turns; try placing an
upside-down plate into the microwave
to cover up the mechanism to stop your
plate of chocolate moving.
This activity is best suited for older (at
least KS2) pupils; it requires some maths
that may be too difficult for younger
pupils. However, with help from a
teacher they may enjoy working with
such ‘big numbers’ and will be amazed
at how close their answer is to the real
thing!
Background science: The distance
between the melted spots is the distance
between a peak and a trough (= half
a wavelength). Double the distance
is the length of one wave. How often
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Accidental discoveries: Organiser’s notes
the waves go by is their frequency. In
a typical microwave oven, 2450 million
waves go by every second. So, the
length of the wave in metres multiplied
by the number of waves per second
gives us the distance in metres that light
and microwaves travel in one second.
The speed of light is exactly 299,792,458
metres per second (the metre is defined
from the speed of light), or about 300 000
kilometres per second (186 000 miles per
second).
Pacemaker
Equipment and advice: You can buy
heart monitors for about £20 from school
science suppliers, or online shops (such
as the Kinetik Monitor Watch from Argos).
Background science: The human heart
must keep a constant flow of blood to
the body’s tissues to supply food and
oxygen and remove waste, especially in
the brain.
The natural pacemaker of the heart
generates electrical signals to stimulate
the heart muscle to contract. In a heart
attack, the muscles of the heart are
deprived of oxygen and some may
die. Cells in the pacemaker may also
be killed so it no longer produces the
necessary electrical signals. When this
happens, an artificial pacemaker can be
used to deliver regular electrical signals
to the heart.
appropriate agar medium.
If you don’t have a heart monitor, pupils
can simply take each other’s pulse –
they may need some help with this.
Background science: Bacteria form
solid colonies containing millions of
cells. Moulds grow hairy structures. If a
mould produces a chemical that inhibits
bacterial growth, bacteria will not grow
near them.
Additional health and safety note: If
pupils decide to measure heart rate
after exercise, check for pupils who suffer
from any conditions which might affect
their ability to undertake the exercise
safely. Do not allow pupils to carry out
this activity unsupervised. Advise pupils to
stop, sit down and report if they feel dizzy
or unwell.
Radioacivity
Equipment and advice: You can buy
sunprint paper in craft shops or online
(such as Amazon); a pack of ten A5
sheets costs about £5.
Sunprint paper is soaked in light sensitive
Berlin green, which washes away when
the paper is rinsed with water. The action
of sunlight on Berlin green causes a light
activated reaction producing Prussian
blue. This is not washed away by water.
The darker the blue colour, the more
complete the reaction that has taken
place.
Penicillin
Equipment and advice: You can buy
pre-poured Petri dishes from suppliers
such as Blades Biological. Malt agar is an
Additional health and safety notes: Wash
hands before and after any microbiology
experiment. Cover any exposed cuts
to the skin with waterproof dressings.
Do not put fingers in mouth and do not
eat or drink in the lab. Avoid touching
face or eyes with hands until after
they have been washed. Open Petri
dishes only for as long as is necessary
(15 minutes should be sufficient). Avoid
breathing or coughing over an open
Petri dish. Don’t touch the exposed agar
medium. Close an inoculated plate with
small strips of clear adhesive tape (see
diagram in pupil instructions). Incubate
the plate upside down. Ensure plate is
carefully labelled on its base. Keep the
plates’ temperatures at or below 30 oC.
Keep incubated plates closed during
examination. Ensure that all used Petri
dishes are autoclaved before being
disposed of – you may need to find a cooperative secondary school or university
to help.
For further notes on the handling and
disposal of microbe material, refer to
CLEAPSS guide G190 for microbiology
activities, and the ‘Be Safe’ booklet from
the ASE.
Vulcanised rubber
Equipment and advice: The rubber
bands should be the same for
comparison. They need to be treated in
different ways – it’s probably best if you
do this beforehand, although with time
and guidance the pupils may help with
the process.
Treatments include: Boiling in water
(makes the rubber stretch more easily),
Soaking in mineral oil for three days or
more (makes rubber stretch more easily,
but not as much as boiling in water),
Freezing (no effect – water molecules
are unable to penetrate the rubber
to form ice crystals), and Exposing to
sunlight (become brittle and snap easily).
Background science: Vulcanisation is
a curing process of rubber involving
high heat and the addition of sulfur or
other curatives. Polymer molecules are
linked to other polymer molecules by
bridges composed of sulfur to sulfur or
carbon to carbon bonds. Springy rubber
molecules become cross-linked to a
greater or lesser extent, making rubber
material harder, much more durable
and more resistant to chemical attack.
It also makes the surface of the material
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Accidental discoveries: Organiser’s notes
smoother and helps to prevent it from
sticking to metal or plastic.
See: http://computer.howstuffworks.
com/mote.htm
technologyreview.com/news/409169/nomore-thumbprints/
Smart dust
Coca-Cola®
Mauve
Equipment and advice: Components for
the circuits can be bought online or from
shops such as Maplins. The water in the
cup needs to be distilled/deionised – you
can buy it from school science suppliers
or from shops such as Halfords (it’s the
same stuff you put in car radiators).
Alternatively, previously-boiled water
should be OK. To make the salt solution,
just dissolve a few spoons of salt in a cup
of water.
Equipment and advice: The preparation
must be done in a suitable food
preparation area. To avoid the use of
knives, lemons can be cut in half and
stored in plastic bags beforehand.
Sodium bicarbonate (sodium
hydrogencarbonate) may be bought
cheaply in chemists or supermarkets
and should not be confused with baking
powder (which also contains acid such
as tartaric acid).
Equipment and advice: How much
can be achieved depends, of course,
on the time available. Here are two
approaches. If time allows, both could
be used.
Background science: Here the objective
is simply to show that electrical devices
can be used as sensors to detect
chemical changes. Motes, also known
as ‘smart dust’, use a small, low cost
computer to monitor one or more sensors
for such things as light, temperature,
position, sound, vibration, pressure,
humidity, acceleration and so on. They
may be switched on and off remotely
and connect by a radio link to transmit
information. At present they are typically
the size of a couple of matchboxes.
Power consumption is the main problem,
so the battery is usually the largest
component. In the future motes are
expected to be a few millimetres in size
and may be used inside the body.
Background science: Sodium
bicarbonate reacts with the citric acid in
the lemon juice to give carbon dioxide.
Teflon®
Equipment and advice: You can buy
Teflon tape (or PTFE tape) from DIY shops.
You may be able to obtain wider rolls
than the usual standard size.
Background science: Teflon’s scientific
name is Polytetrafluoroethylene (PTFE).
The polymer molecules in plastic
shopping bags line up from top to
bottom to resist the weight of the
shopping.
Super non-stick surfaces are being
developed that are self-cleaning.
See, for example, http://www.
H Different plants or plant products and
just one sort of fabric, e.g. cotton.
H Different sorts of fabrics and just one
plant or plant product. If this approach is
taken pupils could be asked to make a
note of the types of fabric by looking at
labels on the clothing, etc.
Pupils might work in pairs. Make sure their
work stations are set out neatly and keep
a close eye on pupils using boiling water.
It’s a good idea to dye the fabrics while
the dye solution is still warm, say about
40 oC.
Pupils can put their dried pieces of dyed
fabric in cold water to see how easily the
dye comes out. Another test sometimes
used is the ‘rub test’. Simply rub the dried
fabric with a clean dry piece of white
fabric. Does it rub off?
crest star investigators
The following two activities count
towards a Crest Award at either Star
or SuperStar level. If you enjoyed these
activities and would like to do more then
why not register for CREST « Investigators
and receive a pack of further activities
and investigations? CREST « Investigators
is a UK-wide award scheme that enables
children to solve scientific problems
through practical investigation.
For more information on how to register
and receive your CREST « Investigator
packs, visit our website at http://www.
britishscienceassociation.org/creststar or
call 020 7019 4943.
Tea and teabags
What do I do?
Get the pupils to talk to a friend about
the questions and the ideas.
Look at some tea bags together. Talk
about making tea.
If possible, let them choose their own
materials.
Check that they understand how to
make tea bags using the pegs. Let them
talk about what makes a good tea bag.
Discuss safety issues when using hot water.
If drawing cups of tea, encourage the
pupils to use lighter or darker browns to
show the tea colour and to draw in tea
leaves.
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Accidental discoveries: Organiser’s notes
Things to look out for
Safety
They need to fix the peg so that the tea
leaves cannot escape through the top.
Pupils may need to practice. Thin or soft
materials are easier to use.
Water from the hot tap will work. Check
its temperature before use to make sure
it is not too hot for pupils to use.
Some materials will absorb a lot of water
and some will tear easily. Encourage
pupils to notice this.
Try to prevent over vigorous dunking and
splashing.
Pupils should not drink the tea.
Encourage pupils to use the same
amount of tea in each bag, the same
sized piece of material, the same volume
and temperature of water, and to dunk
for the same amount of time.
Velcro® (learning from plants)
Encourage pupils to observe differences
in tea colour and the number of
escaping tea leaves.
Give pupils time to explore flat and
screwed up paper and to think about
what might be making a difference to
the way that they fall.
How can pupils share their ideas?
Pupils can draw pictures of cups of
tea. They can stick a piece of the
appropriate tea bag material next to
each picture.
Resources
Loose tea leaves and tea bags, water
from the hot tap (see Safety), clothes
pegs, a selection of different materials
(e.g. tissues, newspaper, kitchen roll,
silk, cotton, tissue paper, crepe paper,
material from a pair of tights), teaspoons,
clear containers, measuring jug, minute
timer, scissors and thermometers,
coloured pencils (including brown).
What do I do?
Check the resources list, including
preparing a spinner and templates if you
think that they might be needed.
Encourage the pupils to make their own
large and small spinners. It is important to
let them explore their ideas on their own.
Have templates available if pupils need
them.
Some may need help to work out how to
cut and fold the spinners.
Now let pupils try the spinners to see
what happens.
Remind them about safety, particularly
about not climbing to drop the spinners.
Give pupils some time to talk about their
observations and ideas. You could show
pupils other spinners with different blade
lengths and ask them to predict how
they will fall.
Pupils can share their ‘best’ spinner or
they can create a display.
Things to look out for
Encourage pupils to drop their spinners
from the same height. This should be as
high as possible so that the spinners can
twirl before they hit the ground.
Very large spinners require a long drop to
see any effect. If they are too flimsy they
will not spin.
Very tiny spinners can spin extremely
quickly.
It is difficult timing the spinners if they fall
quickly. However, if pupils want to try
timing, you should let them have a go to
see if works.
Adding paperclips or Blu-Tack® can
increase spin speed.
Resources
A4 Paper, 30 cm ruler, metre ruler,
paperclips or Blu–Tack®, scissors, one
ready–made spinner to show the
pupils how they work, large and small
templates for spinners (if you think pupils
will need them, click here), stopwatches,
other types of paper and card.
Safety
It can be useful to drop the spinners from
a height greater than a child. However,
pupils should not stand on chairs or
tables to launch their spinners unless
very closely supervised. A library stool or
kitchen steps are better.
Pupils need to handle and carry scissors
in a safe manner.
curriculum links
Working through the activity pack provides
lots of opportunity to engage in practical
work and scientific enquiry. Many areas
of the 5-11 curriculum across England,
Northern Ireland, Scotland and Wales are
touched on, as indicated below:
ENGLAND
Science
H Scientific enquiry
H Life processes and living things –
Humans and other animals (Circulation);
Green plants (Growth and nutrition;
Micro-organisms)
H Materials and their properties –
Grouping (and classifying) materials;
Changing materials
H Physical processes – Electricity (Simple
circuits); Light and sound
NORTHERN IRELAND
The World Around Us
H Interdependence
H Movement and Energy
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Accidental discoveries: Organiser’s notes
H Place
H Change over Time
SCOTLAND
Sciences
H Planet Earth – Biodiversity and
interdependence
H Forces, electricity and waves –
Electricity; Vibrations and waves
H Biological systems – Body systems and
cells
H Materials – Properties and uses of
substances; Chemical changes
WALES
Knowledge and Understanding of the
World (3-7 year olds)
H Myself and other living things
H Myself and non-living things
Science (7-19 year olds)
H Communication; Enquiry
H Interdependence of organisms
H The sustainable Earth
H How things work
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