Science Experiments
Do NOT PRESUME that you are allowed to carry out any of these experiments. You
must always seek permission of your head of department. If you are not confident,
get someone else to demonstrate for your class, or show the video!
A number of these experiments are extremely dangerous and should only be
attempted by trained staff, use recommended quantities whilst taking appropriate
precautions and under CLEAPPS, and any other local, guidance rules. DO NOT be
tempted to ‘make it a little more exciting’ by increasing the recommended scale of a
reaction. Your, and more importantly, your students safety must always be
paramount. You could end your career very quickly by unprofessional conduct and
God forbid you should do actual bodily harm. Use your laboratory technicians!
These people are usually an excellent source of information, the likelihood is they
have set up the demonstration, if not performed it before. You also need to ensure
that what you’re about to demonstrate has not recently been banned. Always check
with more experienced colleagues and you head of department. NEVER attempt
any experiment in front of a class that you have not tried and tested before.
Any added safety comments to be found in this document are over and above
CLEAPPS or any local requirement. They are included as a result of experience and
indicate what might else be considered or what may go wrong, even when the
experiment is correctly performed.
A number of these demonstrations may irritate a pre-existing lung condition
(asthma etc) – be aware of this possibility.
Remember – you need to develop a little showmanship - tell them it‟s not
dangerous then act a little nervous. Ask misleading questions to help them think „a
balloon cannot possibly…‟
For me the best demonstration is a little scary, but always controlled.
Above all convey a love for science, it is infectious!
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Balloons
Water balloon – partially fill balloon with water, inflate and seal. Hold a candle
under the balloon, taking care only to heat where the water is. Soot will show you
were not cheating, but the balloon will not burst. You can do a similar trick making
a paper box, and filling with water. Heat over a roaring Bunsen and make tea. The
paper (provided it doesn‟t leak) can be seen to be glowing orange underneath
(actually the mesh holding it).
Blanket on the floor (to protect from grit), four balloons (quality not the very thin
ones). MDF board on top (1x1 m doesn‟t really matter). Get the first student to
stand on top. „Big up the risk‟ (at the same time taking care not to trap your
fingers underneath the board. Great fun to see how many you can balance on the
board – probably safest to do with single sex….
Propulsion – tape a balloon to a straw, and watch it zip along a line. Lot of
variations on this – toy cars…
Match head
Straighten a paper clip, and twist around a match, close to the head. Suspend on
the mouth of a Bunsen and light the Bunsen. The match should survive happily in
the cold blue cone.
Laser pens
– fantastic for lots of demos, keep a careful track of them with students Ebay:
Green Laser Pointer & Star Projector, also simple pens, 3 colours at the moment.
Ice cube blocks
Two seemingly identical black blocks (in the range of 3cm high, 10x5 wide). Do not
let the student pick them up or the difference will be immediately apparent
(density). One feels warm to the touch (made of wood), the other cold (metal). Put
an ice cube on each and watch what happens. (conductor vs non conductor, but
counter intuitive as one might expect the warm block to melt faster).
Xylene cyanol
An indicator you may have lurking in the preproom, or scrounge from the local
college/uni. Solution in 1M HCl in a volumetric flask, port decanter or similar.
Green at the top, red at the bottom (best lit from underneath using an OHP).
Explanation – email me.
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Singing rods
1m metal rod (aluminium is easiest), about 5mm diameter - B&Q.
Hold the rod firmly, dead centre, between thumb and first finger. Apply a little
violin rosin to you other thumb and finger, and draw firmly down the rod. You
should hear it „sing‟ (takes a little practice). Halve the distance between the
thumb/finger and the rod and try again.
You should be able to get at least 3
notes.
IR camera
IR webcam can se into the IR. Use a cloth/bag to remove daylight and look at the
security features of a banknote (the Queen‟s head, only present in £5 note). Will
also show-up veins (difference in temperature vs. skin).
Ebay: search for Night Vision Web cam
Exploding water
U-tube containing 4M sulphuric acid fitted with two platinum electrodes. Apply
enough voltage (20+ typically) to split the water – bubbles at each electrode.
Use polypropylene tubes (rubber perishes) to join the two ends of the tube, via a
t-piece and into a single tube which is under a bubble solution (soap/glycerol/water
– see internet). The bubbles catch hydrogen and oxygen in perfect harmony, ready
to be reunited with a (VERY) loud bang. Protect your own ears as you will be
closest – inverse square of the distance from the source (I use plugs, or at least
stick a finger in the closest ear).
Caution – the sulphuric acid will get very hot.
This is great for discussion of the hydrogen economy
Dragons breath
Gas-canister blow torch from B&Q (always handy). Fill an empty spray bottle with
methanol adding the salt of your choice (lithium chloride, boric acid etc.). spray
across the blow torch flame creating Dragons Breath. Best in a darkened room. Do
not set fire to the bottle in your hand. This will quickly fill the room with smoke –
do not over use.
You can create a lesser version using methanol in evaporating basins. Again add
the salt of your choice to produce beautiful colours.
Copper coin
2p copper coin (or similar) is suspended from a glass rod using high temp wire nicrome should do. Holding the coin in tongs, heat over a roaring Bunsen until red
hot, the carefully suspend (a slight angle works best) just above a small volume of
propanone in a beaker/conical flask). Works best in a darkened room. The coin
with continue to glow with „clouds of orange‟ sweeping across the surface, until all
the propanone has evaporated.
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Caution: the coin/ stay very hot (? 400°C) for a long time, the beaker too becomes
hot. The vapours will cause headache (contains ethanol)
Exploding wax
Wax from a candle kit, or grated is place in a test tube (ca 3cm deep), and heated
to a gentle boil over a roaring Bunsen. The test tube is plunged into cold/iced water
to the height of the wax (no more or it kills the reaction). The cold water
cracks/shatters the tube and the column of steam carries the wax up into the air as
it condenses as white clouds. At about 0.5m, the energy released as the wax goes
from gas to solid causes spontaneous combustion and a resulting fire ball.
Caution: wear a glove (wax vapour is very hot), cover the desk, use the same
beaker as it is difficult to clean. DO NOT BE TEMPTED TO SCALE UP, NOT EVEN TO
A BOILING TUBE.
Silly putty
Syllabus Links: Fun experiment – fits best with 21st C polymers – borax crosslinks
the PVA polymer to change its physical properties, depending on the degree of
crosslinking the polymer goes from a viscous liquid to gel (silly putty) to a rubber.
Method: PVA, water, borax solution, food dye. 25 ml PVA adhesive, 20ml water
(you mar add a few drops of one or more food dyes for effect), 15ml borax solution
(1:4 borax:water). Add water/dye to PVA and stir. Add borax solution and stir.
This should give „silly putty‟, the reaction is relatively slow, and the product will
thicken with stirring or as it is played with. Adding more borax solution will further
crosslink the polymer, turning it into a rubber. The age and quality of the PVA and
borax make quantities rather in exact. A small trial should give the required
amounts.
Safety: Silly putty may cause irritation if directly handled. Insist that students wash
thoroughly with soap and water after touching silly putty. Students are not allowed
to remove anything from the laboratory. However, they may be reluctant to part
with a rubber ball they have made.
Update – magnetic silly putty … add a spoon full of black iron oxide
Fe3O4 – the expensive black stuff, not common red rust Fe203. This will create silly
putty the will move with a super magent….
Possible source: ebay Black iron oxide
See: http://www.youtube.com/watch?feature=player_embedded&v=UlCm9Pni6ME
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Green fire
Syllabus Links: Energetic reactions in KS3 chemistry, displacement reactions.
Applied/Additional science
Method: Ammonium nitrate (3g), salt (0.5g) – grind these together in a mortar and
pestle. Add zinc powder (7g), grind again. Transfer to crucible, add few drops water
– stand clear.
As soon as the zinc has been added, take EXTREME care as the least drop of
water will initiate this reaction.
Safety: „Don‟t try this at home‟ ammonium nitrate is readily available in most
garden supply centres as it is a common fertiliser. Hopefully students will not make
this link. This is an extremely vigorous reaction, even a drop of sweat could initiate
it.
Nitrogen triiodide
1.
The first step is to prepare the NI3. One method is to simply pour up to a gram of iodine crystals into a a small
volume of concentrated aqueous ammonia, allow the contents to sit for 5 minutes, then pour the liquid over a
filter paper to collect the NI3, which will be a dark brown/black solid. However, if you grind the pre-weighed
iodine with a mortar/pestle beforehand a larger surface area will be available for the iodine to react with the
ammonia, giving a significantly larger yield.
2.
The reaction for producing the nitrogen triiodide from iodine and ammonia is:
3I2 + NH3 -> NI3 + 3HI
3.
You want to avoid handling the NI3 at all, so my recommendation would be to set up the demonstration in
advance of pouring off the ammonia. Traditionally, the demonstration uses a ring stand on which a wet filter
paper with NI3 is placed with a second filter paper of damp NI3 sitting above the first. The force of the
decomposition reaction on one paper will cause decomposition to occur on the other paper as well.
4.
For optimal safety, set up the ring stand with filter paper and pour the reacted solution over the paper where the
demonstration is to occur. A fume hood is the preferred location. The demonstration location should be free of
traffic and vibrations. The decomposition is touch-sensitive and will be activated by the slightest vibration.
5.
To activate the decomposition, tickle the dry NI 3 solid with a feather attached to a long stick. The decomposition
occurs according to this reaction:
2NI3 (s) --> N2 (g) + 3I2 (g)
6.
In its simplest form, the demonstration is performed by pouring the damp solid onto a paper towel in a fume
hood, letting it dry, and activating it with a meter stick.
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Tips:
1.
Caution: This demonstration should only be performed by an instructor, using proper safety precautions. Wet NI 3
is more stable than the dry compound, but still should be handled with care. Iodine will stain clothing and
surfaces purple or orange. The stain can be removed using a sodium thiosulfate solution. Eye and ear protection
are recommended. Iodine is a respiratory and eye irritant; the decomposition reaction is loud.
2.
NI3 in the ammonia is very stable and can be transported, if the demonstration is to be performed at a remote
location.
3.
How it works: NI3 is highly unstable because of the size difference between the nitrogen and iodine atoms. There
is not enough room around the central nitrogen to keep the iodine atoms stable. The bonds between the nuclei
are under stress and therefore weakened. The outside electrons of the iodine atoms are forced into close
proximity, which increases the instability of the molecule.
4.
The amount of energy released upon detonating NI3 exceeds that required to form the compound, which is the
definition of a high yield explosive.
What You Need:
up to 1 g iodine (do not use more)
concentrated aqueous ammonia (0.880 S.G.)
filter paper or paper towel
ring stand (optional)
feather attached to a long stick
Pop Can Collapse
Syllabus Links: Energy transfer, pressure
Method: -Put a little water in the can, heat and invert into bowl of cold water – can
collapses. Physics – pressure the can becomes filled with hot water vapour,
inverted in the bowl, the temperature drops
Safety: Students can find it difficult to grip the can, even more so to invert it into
the bowl of cold water. Inverting the can risks spraying boiling water.
Empty soda cans, tongs, bowl of water, Bunsen, water.
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Pocket Rockets
Syllabus Links: acids and alkali, pressure action/reaction.
Method: Citric acid, sodium carbonate (2:3), grind as necessary. Wrap carb/citric in
tissue and put into the mouth of a old plastic 35mm film canister with water in the
bottom. Seal the lid firmly and invert - explodes as CO2 is released.
Citric can be replaced with lemon/acetic (vinegar).
Safety: Can be messy, and surprisingly explosive – eyes!.
Thermit
Syllabus Links: energetic reactions, energy transfer
Method:
Thermit reactants (enough for TWO demonstrations):
Iron (III) Oxide
3.74g
Aluminium powder
1.26 g
Magnesium powder
3 spatula
Barium Oxide powder 3 spatula
Magnesium ribbon
Mix the iron and aluminium, then cover with a mixture of the magnesium and
barium oxide. The Magnesium forms a wick to set off the reaction.
Safety:
Thermit – messy and hot (molten iron 1500C +)! Potentially this is one of the most
dangerous of all the „classic‟ reactions. Can be unpredictable and explode from the
pot.
Methane Bubbles
Syllabus Links: Energy transfer, combustion
Method: There are endless variations: Methane, long rubber hose. The „bubbler‟ is
made from an inverted plastic soda bottle, cut in half - discarding the base. The
cap of the soda bottle is replaced with a rubber bung through which has been
inserted a glass tube. The end of the tube has been bent over to form a hook which
is below the level of the bubble mixture. Methane is blown through the bubble
mixture, via a hose connected to the end of the tube.
Bubble mixture: many folk have their own secret recipe, but generally:
1/8 part dishwashing liquid, 1 part water, 2 tbs glycerine. You may wish to
„Simpsonize‟ the experiment by adding blue food dye to the bubbles and a picture of
Marge‟s face to the bubble blower. Ensure the students hands are we, and no
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bubbles are under their hands. Another variation is to „shake off‟ the bubbles and
ignite in mid air.
Safety: If you find you‟ve got a headache at the end of this, you have insufficient
ventilation. Do not be tempted to over-do this one. Do not forget to wet the
students hands, and have the hand stretched out fully and horizontal. It is essential
they wear goggles. The flames tend to mushroom into the students face. The
experiment goes wrong when the students panic and drop their hands, bringing the
flames close to the face. Have a sink of cold water near to hand, the odd student
will think they were burned.
Gas explosion (various)
Syllabus Links: Energy transfer, combustion
Methane, long rubber hose, heat proof mats, Pringles tube, plastic soda bottle,
Method: See accompanying videos – much easier than explanation.
Safety: methane/air is relatively safe. Should only be carried out in well ventilated
laboratory.
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Pringles ‘bomb’
Empty a tube of Pringles, keeping the plastic lid. Taking care not to otherwise
damage the tube, punch/drill a 10mm (or so) hole in the metal base. In the side of
the tube, near the top, drill/punch another hole, 2-3mm in diameter (important).
Put your finger over the large hole in the base and fill the tube with methane from a
rubber hose. Turn off the gas and push the tube onto the plastic cap, which is now
the base. Remove your finger and light the gas, forming a Pringles candle.
Discuss why the flame is yellow, yadda, yadda. The students will forget about the
tube as it apparently „goes out‟. Sometime later the gas/air in the tube that has
„gone out‟ reaches an explosive limit and the can jumps up with a whoosh. (safe to
do on a desk in front of students. They will ask to do it again. Shake the can to
replace the air inside and „set it off again‟. Waiting for it to pop is worse than the
first time.
Methane + oxygen
Syllabus Links: energy transfer, combustion, rocket design.
Method: Using a PET soda bottle of MAXIMUM 500ml capacity, fill with 2/3 oxygen
to 1/3 methane. This is best done by marking the bottle first, then filling and
inverting in water. Measure the required gas volumes by displacement of water.
Close the bottle off using a balloon. Support the bottle in a suitable holder, and
melt through the balloon with a gas lighter.
Safety: Only use carbonated drinks bottles as PVC bottle are significantly weaker.
The explosion that will follow should propel the bottle 30 metres or more. The
explosion is EXTREMELY LOUD, especially for the staff member melting through the
balloon. I have seen this done in a large lab, but would recommend it only be
done outside.
Screaming Jelly babies
Syllabus Links: energy transfer, combustion, rocket design.
Method:
5-10 g potassium chlorate in a boiling tube (will be destroyed), jelly babies
Melt the chlorate with a Bunsen, then drop in the jelly baby.
Safety: It is suggested that this can be done in an open lab, but I would never
recommend this, on the basis of the gas/smoke produced, if nothing else. I only
ever do this experiment in a fixed or portable fume hood. Occasionally the Jelly
baby fights back, and refuses to slide down the tube. You are now in the situation
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of a fire work that has not gone off. If you try to poke the jelly baby down the
tube, you risk having your hand in the jet of the reaction! It is safer to change the
angle of the tube.
Balloon tricks
Syllabus Links: Upthrust, pressure, 21st C materials and their properties.
Action/reaction
Method: There are 101 balloon tricks. Blow up a balloon and stick a pin in it. It
explodes. Keep threatening to do this…….The old trick is to put sellotape on the
balloon and push a knitting needle through this. The tape stops the tear in the
rubber propagating. At then end of the balloon, there is a small „nipple‟ where the
rubber is thicker – it is possible to push a sharp pin/skewer through this without
popping the balloon. – Why?
Try to push a balloon under water….
Blow up a balloon and put it over a night-light candle. The balloon bursts and the
candle is snuffed out. There is a lesson there alone – why….
Partially fill a balloon with water and then blow it up. Hold the balloon over the
candle – nothing happens, why? Show the soot on the base of the balloon – this is
no trick. A variation of this is to make a paper boat and fill with water. Put this
over a roaring Bunsen. The paper will not burn whilst there is still water in the
boat. You may wish to add a tea bag for effect.
Attach a balloon to a paper plane attached to a straw. Pass a thread through the
straw and use the balloon to project the plane along the thread, across the class
room. Great fun.
Inflate a balloon and statically charge it by rubbing or using a Van de Graff.
Hold the balloon near a slowly running stream, of water – why does the water bend?
How could you get the water to bend in the opposite direction?
Better still….. Hold the charged balloon near a slowly pouring stream of golden
syrup – with care you can get the syrup to bend horizontally!
Water trick
Syllabus Links: „Flogistan theory‟, pressure
Method: Put a small amount of water, coloured with food dye, in a shallow plate.
Use a wedge of apple or orange to hold 4 matches. Place the wedge with the
matches in the water and light. Quickly cover the matches with a glass ands press
down firmly. The water is sucked from the plate into the glass.
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Flaming money
Syllabus Links: Combustion
Method: Soak paper money in a 50% solution of water/ethanol. The ethanol burns,
but the paper is protected by the water. More spectacular (and risky…) is to burn a
scarf instead.
Safety: Do not ignite the beaker, or anything else.
Tea Bags
Syllabus Links: Combustion
Method: Unwrap the tea bag to give a hollow tube. Put the tube on something
valuable (£5) and set fire to the top. The panic comes when the flames approach
the money, but….
Safety: Watch where the ignited bag goes.
Rubens Tube
Syllabus Links: Pressure, sound
Method: Signal generator, Rubens Tube, gas supply. I have never seen a Rubens
tube for sale, but they are relatively easy to make (email for instructions). The
Rubens tube is essentially a tube forming a gas grill. One end for the tube is
closed off with a plastic membrane which is vibrated by a speaker. Us the signal
generator to discuss the range of human, young/old hearing.
Safety: The tube gets hot. Residual gas in the tube can linger and smell.
Magnetic Rail gun
Syllabus Links: action/reaction, magnetism
Method: Easily constructed from electrical conduit, cable ties and neodymium
magnets. The last ball leave the gun faster than the entering ball, appearing to have
gained energy…..
Ferromagnetic Liquid
Syllabus Links: Magnetism
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Method: Ferrofluid can be bought from Ebay. Cover with 50% IPA/deionised water
in a glass jar.
Safety:
Neodymium magnets can cause pinch injuries, wipe data or smash the vessel the
Ferrofluid is in.
Cannon Fire
1. Measure 20 ml ethanol, 20 cm3 hydrogen peroxide solution into a crystallising
dish on a heatproof mat. Place a second heatproof mat to one side.
2. Light the solution with a taper
3. Scoop the end (tiny amount!) of a spatula of potassium permanganate and tip it
into the crystallising dish. You should see an increase in the size of the flame and
hear a popping sound
4. Extinguish the flame by placing the second heatproof mat on top of the
crystallising dish
5. Wash everything up (solution can go down the sink).
You will have to experiment with the quantity of peroxide as the concentration is
rarely what is „says on the can‟, having sat in the fridge for the last year.
Potassium permanganate oxidises hydrogen peroxide to produce oxygen (NB.
Contrary to popular belief, the potassium permanganate is NOT a catalyst). Ethanol
burns to give a transparent blue flame. When you add the potassium
permanganate, it reacts with the hydrogen peroxide to produce oxygen in small
“pockets”.
2KMnO4 + 3H2O2 2MnO2 + 2H2O + 3O2 + 2KOH
�
�
These pockets of oxygen increase the intensity of the reaction and you get the
cannon fire noise as the pockets of oxygen hit the flame.
If you look carefully when the flame erupts, you can sometimes see a violet colour.
This is because there is a metal in a flame – potassium. Potassium gives a violet
flame colour.
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Other (incomplete)
WHAT YOU NEED
To do this experiment you will need
a saucer
milk
food colouring (four different colours)
detergent.
W H A T T O DO
1. Fill the saucer with milk.
2. Add one drop of each food colour to the milk around the edge of the saucer.
3. Add one drop of detergent into the centre of the saucer.
W H A T ' S H AP P E N I NG
The colours swirl and zoom around the saucer.
Milk stays together as one liquid because of surface tension. This acts like a skin and keeps the milk in a puddle.
When you add the detergent, it breaks the surface tension of the milk in one spot.
The pull of the surface tension from the milk at the edge of the saucer causes the milk in the centre to move to the
outside, taking the colours along with it.
The colours keep moving until the detergent stops affecting the milk.
WHAT YOU NEED
To do this experiment you will need:
four clear glasses, each half full of water
cooking oil
food colouring – red or blue show up best
liquid detergent.
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W H A T T O DO
1. Add a few drops of food colour to the first glass and stir. Notice how well the colour mixes with the
water.
2. Pour some cooking oil into the second glass. Does it mix in like the food colour did? Try stirring the oil
and observe what happens. The oil will eventually rise to form a layer on top of the water.
3. Pour enough cooking oil into the third glass to form a layer on top of the water approximately five
centimetres thick. When the oil layer has settled, add a few drops of food colour. Don‟t stir. Watch how
each drop behaves as it hits the oil layer.
4. Now mix everything in together. What happens to the drops of colour? Some tiny drops of colour will
probably stay in the oil layer. Watch what happens to them after a while.
5. Create the same oil and water mixture in the fourth glass, with several drops of food colour. Add a
teaspoon of dishwashing detergent and stir vigorously. What is different this time? Notice the colour of
the oil layer. Is it the same as the water layer?
W H A T ' S H AP P E N I NG
Oil and water don‟t mix. Even when you stir them together, they will soon separate. The oil, which is lighter (or
less dense), rises to the top. Food colouring is water-based, so it mixes easily with water, but can‟t mix with the
oil. Did you notice how the drops of food colour behaved when they travelled through the oil? Sometimes the
food colour forms perfect little beads, which slowly drop through the oil layer.
M I X I T UP
You can make oil and water mix by breaking them down into tiny drops that won‟t re-form. The homogenised
milk that we buy from the shop is made this way. Milk from the cow naturally separates into cream (oil based) on
top and skim milk (water based) on the bottom. Before milk is bottled, it is squirted through a sieve at high speed.
This breaks down the two liquids into tiny drops that won‟t separate.
Any mix of two liquids similar to this is called an emulsion. An emulsion consists of millions of tiny droplets of
one liquid suspended inside another liquid.
Oil based paint is an emulsion. Many medicines and cosmetics are as well. They are mixtures of oils and waterbased substances, held together by an emulsifier.
Egg yolk is a natural emulsifier. Artists use it in tempera paint to hold the various ingredients together. It is also
used in making mayonnaise.
Now for that recipe:
SALAD DRESSING
To make your own salad dressing you will need to gather the following items:
1/4 cup fresh lemon juice
1/3 cup olive oil
salt and pepper to taste
1 teaspoon seeded mustard.
Place all ingredients in a screw top jar and shake until well mixed.Taste it.
Try adding other flavourings, such as chopped chives or garlic, if you like. You can also use vinegar instead of
lemon juice. Do what all good scientists and chefs do – experiment!
Pour over salad vegetables and toss.
MAYONNAISE
Mayonnaise is a bit trickier. It uses an egg yolk to emulsify vinegar or lemon juice with olive oil.
You will need to gather these items to make it:
1 cup of light olive oil
1 egg
1 lemon
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a pinch of salt and pepper
water.
Open the egg and separate the yolk from the white (only the egg yolk is used in this recipe). The egg yolk
contains an emulsifier called lecithin which helps form the mayonnaise emulsion.
Mix the juice of one lemon, the egg yolk, salt and pepper with a whisk. Continue to whisk the mixture and slowly
add the olive oil. Do not add the oil too quickly, or the mixture will not form an emulsion.
If the emulsion is too thick you can add a small amount of water to thin it. If the emulsion doesn‟t begin to
thicken after adding a quarter of the oil, you will need to start again.
Once you have finished adding the oil, you can adjust its taste with extra lemon, salt, pepper, or even mustard.
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WHAT YOU NEED
To do this experiment you will need:
fresh red cabbage
a sharp knife
a cutting board
hot tap water
seven clear plastic disposable cups
seven plastic spoons
a large plastic bottle
a range of the household substances which may include:
strongly acidic. For example, powdered toilet cleaner.
acidic. For example, vinegar, lemon juice, white wine, lemonade or citric acid.
weakly acidic. For example, cream of tartar.
neutral. For example, pure water, shampoo or baby shampoo.
slightly basic. For example, bicarbonate of soda.
basic. For example, milk of magnesia, washing soda or floor cleaner.
strongly basic. For example, dishwasher liquid or powder.
W H A T T O DO
1. Using a sharp knife and cutting board, finely slice three or four red cabbage leaves.
2. Place the cabbage leaves in the plastic bottle, half fill the bottle with hot water and screw the lid on
tightly.
3. Shake the bottle for a few minutes until the water becomes a deep purple colour. Leave the solution to
cool.
4. Strain the solution and add sufficient water to the solution to make about one litre.
5. In each of the cups, place a small amount of one of the above household substances in the following
order: strongly acidic; acidic; slightly acidic; neutral; slightly basic; basic and strongly basic.
6. Now half fill each cup with the red cabbage water and stir the solution. If arranged in order, the jars
should display a spectrum of colours from cherry red (strongly acidic), pink-red (acidic), lilac (slightly
acidic), purple (neutral), blue (slightly basic), green (basic) and yellow (strongly basic).
W H A T ' S H AP P E N I NG
The things we eat and drink are all acidic, and the things we use for cleaning are basic. This is because basic
substances taste unpleasant, but a cleaning agent usually needs to be basic to remove dirt and grease.
Substances that are acidic or basic make the eyes sting, so baby shampoo is made neutral.
WHAT YOU NEED
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To do this experiment you will need the following items:
paper towel
scissors
a jar
felt-tipped pens and markers
two paper clips
water.
W H A T T O DO
This is what your experiment should look like.
1. Cut some absorbent paper (such as paper towel) into strips about 2 cm wide. The length isn't really
important and will depend on the size of the jar you hang them in.
2. Draw a small circle 1 cm from the bottom of the paper with different black markers or felt-tipped pens.
3. Fill a clean jar with about 1 cm of water and carefully place the paper into the jar making sure that the
bottom of the paper is in the water. The circle must be ABOVE the water level. Use paper clips to hold
the paper upright in the jar. Watch the water rise up the paper.
4. After a few minutes remove the paper from the jar. Notice how different colours in the ink travel up the
paper at different speeds.
5. Now try some different colour pens and markers. Can you see any differences?
6. Did you have any pens for which the ink did not separate? If so, repeat the experiment using methylated
spirits instead of water in the jar. Try out a variety of pens. Can you see any differences?
The method used to compare inks is called chromatography. It involves separating the ink in each of the pens. As
the solvent (water) rises up the paper, the different colours of the ink separate.
Ask your family to play your suspects. Have them use specific pens for the job and see if you can figure out
which ink comes from which pen and nab your suspect!
WHAT YOU NEED
To do this experiment you will need:
cornflour
food colouring
a small mixing bowl
water.
W H A T T O DO
1. Pour some cornflour into a mixing bowl.
2. Stir in small amounts of water until the cornflour has become a very thick paste.
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3. To make the slime the colour of your choice, thoroughly stir about five drops of food
colouring into the mixture.
4. Stir your slime REALLY slowly. This shouldn't be hard to do.
5. Stir your slime REALLY fast. This should be almost impossible.
6. Now punch your slime REALLY hard and fast. It should feel like you're punching a
solid.
You can keep your cornflour and water mixture covered in a fridge for several days. If the
cornflour settles, you need to stir it to make it work well again.
W H A T ' S H AP P E N I NG
Anything that flows is called a fluid. This means that both gases and liquids are fluids.
Fluids like water which flow easily are said to have low viscosity, whereas fluids like cold honey which do not
flow so easily are said to have a high viscosity.
Cornflour slime is a special type of fluid that doesn't follow the usual rules of fluid behaviour. When a pressure is
applied to slime, its viscosity increases and the cornflour slime becomes thicker.
At a certain point, slime actually seems to lose its flow and behave like a solid. Cornflour slime is an example of
a sheer-thickening fluid.
The opposite happens in sheer-thinning fluids; they get runnier when you stir them or shake them up. For
example, when toothpaste is sitting on a toothbrush it is pretty thick, so you can turn the toothbrush upside down
and the toothpaste doesn't fall off.
But if it was that thick when you tried to squeeze it out of the tube, there is no way you could manage it.
Fortunately, toothpaste gets runnier when you are squeezing it out of the tube. Other sheer-thinning fluids
include:
blood
paint
ballpoint pen ink
nail polish.
Although there are lots of sheer-thinning and sheer-thickening fluids, nobody has a really good idea why they
behave the way they do.
The interactions between atoms in the fluids are so complicated that even the world's most powerful
supercomputers can not model what is happening. This can be a real problem for people who design machinery
that involves sheer-thinning fluids, because it makes it hard to be sure if they will work.
WHAT YOU NEED
To do this experiment you will need the following:
a helper
a tin container with a tin lid, such as a coffee tin
four long pencils
a metal bottle cap (a soft drink bottle cap is less effective)
strong sticky tape
adhesive putty (Blu-Tack or similar).
W H A T T O DO
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diagram of the Cracking Fun experiment
1. Fill the container with water until it is overflowing and press the lid on.
2. Place the metal bottle cap on the centre of the lid and secure it with a small piece of adhesive putty.
3. Place three of the pencils next to each other on the table and tape them together to make a flat platform.
4. Rest the container on the pencil platform so that the pencils poke out on both sides.
5. Place the fourth pencil on top of the bottle cap and fasten it with a bit of adhesive putty.
6. As one person holds all the pieces together, use strong tape to strap the top pencil tightly to the pencil
platform on either side of the tin, and then place in the freezer.
Have a look after 24 hours (if you have used a large container it may take 48 hours). Marvel at the power of ice!
W H A T ’ S H AP P E N IN G
Water is one of a few chemicals that expands when it changes from liquid to solid. As water cools, it contracts
like any other substance – the molecules slow down, they have less energy and get closer together.
But as its temperature drops below four degrees Celsius, water begins to expand. The molecules begin forming
stiff bonds with their neighbouring molecules, which push them outwards to form a hollow structure, or crystal
lattice, which can float in liquid water.
As water freezes and expands, it can exert incredible pressure. For example, it has enough energy to burst open
the walls of plant and animal cells, crack rocks, burst water pipes and crack your pencil!
Plant and animal cells contain water. As this water turns to ice, the cells expand, causing them to burst. In
mountain and polar explorers, such burst cells can cause frostbite, which is an irreversible condition. Also, severe
damage to fruit and vegetable crops can occur when sudden cold snaps cause plant cells to burst.
APPLICATIONS
People in cold climates need to add anti-freeze to the coolant in their motor vehicles. The anti-freeze lowers the
freezing point of the coolant beyond the coldest temperature that the vehicle will be exposed to. This means that
the coolant does not freeze solid and cause damage to the engine.
Some people believe that they can „cheat death‟ by having themselves cryogenically frozen. The idea is that if
you die from an incurable disease such as cancer and have yourself frozen, you can be re-animated in the future
once people discover a cure.
People who are cryogenically frozen are kept at temperatures well below -196° Celsius using liquid nitrogen. If
they were to be placed straight into liquid nitrogen, all the cells in their body would freeze and burst. To prevent
damage to the cells, all the water in the body is removed and replaced with a glycerol-based mixture called
cryoprotectant, which is similar to antifreeze.
So far, dozens of people have been cryogenically frozen but no one has been reanimated – the technology to do
so is yet to be discovered!
WHAT YOU NEED
To do this experiment you will need the following items:
a large glass jar with a lid
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a thin piece of string
Blu-Tack (or similar)
a sugar crystal
1 - 2 kg of sugar
food colouring (optional)
a saucepan.
W H A T T O DO
diagram of the Crystal Grower experiment
1. Drill or punch a small hole through the lid of the jar (you may need an adult to help you). Thread the
string through the hole. Secure the strand with a small ball of Blu-tack, covering the top of the hole or
alternatively tie a knot above the hole. Tie a good-sized sugar crystal (seed crystal) to the other end of the
string.
2. Place ¾ cup of water in the saucepan, bring it to the boil, then reduce to a simmer. Pour sugar into the hot
water until no more sugar will dissolve. If you do not add enough sugar, the solution will not become
'super-saturated'. Turn off the heat and allow the sugar solution to cool. Don't touch or move the
saucepan, as the sugar solution will be extremely hot.
3. Once the solution is cold, pour it into the jar until it is approximately ¾ filled. Poor the remaining
solution into a spare container for later. Secure the lid, ensuring that the strand and sugar crystal are in
the solution.
4. Place the jar in a cool location, such as a cupboard. Check the crystal each day. If the crystal hasn't grown
for a day or two, replace the solution with remaining sugar solution, or make some more in a saucepan.
The crystal needs to sit in a super-saturated solution to continue growing. Time and patience are
required because crystals are slow growing. The crystals in the photo at the top of this page were growing
for about a month. You may want to leave yours to grow for more than a month. The crystals will
eventually reach a point where they will stop growing.
Once your crystal has become large enough, you can remove it from the string.
For added flair, add food colouring to the water to create colourful crystals. (A small drop of the colouring is
sufficient.)
W H A T ' S H AP P E N I NG
A solution is a mixture of a solute and a solvent. In this example, the solute is sugar and the solvent is water. If
you add a small amount of solute to the solvent, typically the solution is under-saturated. Adding more solute will
cause the concentration of the solution to increase, until you cannot dissolve anymore solute. The solution is now
called saturated.
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By heating the solution it is possible to dissolve more solute, making the solution super-saturated. This is an
unstable state for the solution and as soon as conditions change (for example the temperature lowers), some of the
solute will reappear in solid form - precipitation.
To precipitate, the dissolved solute looks for a 'seed' to build upon. In the case of our experiment, it uses the
sugar crystal. Over time, more of the solute precipitates on the outside of the seed, layer upon layer, forming a
larger crystal. Once the solution returns to a saturated state, the crystal stops growing.
Creating a seed crystal
If you need a seed crystal large enough to tie on the end of your string, here's an idea. Half fill a jar with water
from the tap and stir in a few tablespoonfuls of sugar until the solution is saturated. Tie a piece of string to a
pencil and balance it over the top of an open glass jar with the string hanging in the sugar solution. Place the jar
in a sunny position and within a few days you should have a number of good-sized seed crystals.
WHAT YOU NEED
To do this experiment you will need the following:
a tall glass or plastic container
some vegetable oil
ice (try adding some food colouring to make it easier to see).
W H A T T O DO
1. Fill the glass with oil.
2. Drop a block of ice into the glass. The ice should float in the middle of the oil.
3. Watch the ice as it melts.
You will find drops form on the ice, then drop off to fall slowly through the oil. As the drops form and fall, the
ice will rock from side to side and move up and down.
W H A T ' S H AP P E N I NG ?
This activity is all about density. The density of a material is how much a given volume of that material weighs.
For example, one cubic metre of liquid water weighs 1000 kg, so it has a density of 1000 kg/m³.
When you drop an object into a liquid, it feels the forces of:
gravity, which pulls it down
buoyancy, which pushes it up.
When you drop something into a liquid, it displaces some of the liquid (pushes it out of the way). An object
placed in a liquid feels an upward force equal to the weight of the liquid it is displacing. This force is called
buoyancy.
If the weight of the object is less than the weight of the liquid it is displacing, it will float. If it is greater, it will
sink. Another way to say this is that if the object is less dense than the liquid, it will float, but if it is denser it will
sink. This is even true for liquids. Liquid water is denser than oil, so the oil floats on the water.
Water is weird stuff. We don't normally notice it, because water is so common, but water does some things that
almost no other chemical will do. One of the ways water is strange is that it is less dense as a solid than as a
liquid.
Ice and vegetable oil have almost the same density, around 920 kg/m³, so a block of ice dropped into oil will
barely move. As the water melts, it turns into denser, liquid water. The water tends to stick to the ice for a while
before it drops off. If there is enough liquid water on the ice, then the density of the ice and water together is
greater than the oil, so they will sink. Once the drop of water falls off the ice, the ice floats up again.
It's a good thing that ice floats on water. In winter, some rivers and lakes freeze on the surface. If ice was denser
than water, then the rivers and lakes would freeze from the bottom up, which would kill plants growing in them
and starve most of the fish and other marine life.
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WHAT YOU NEED
To do this experiment you will need the following items:
a tall clear jar or PET bottle
golden syrup or honey
water
oil
screws, paperclips, and any other small objects
ice cubes
food colouring
detergent.
W H A T T O DO
1. Carefully pour some golden syrup, water, and oil into the container in that order. You might want to add
food colouring to the different layers to be able to see them better. What do you see?
2. Drop in the small objects. Do they reach the bottom? Try dropping in the ice-cubes.
3. Add a drop of detergent. What happens?
W H A T ’ S H AP P E N IN G
Diagram of the Density Column experiment
Golden syrup, water, and oil have different densities so they don‟t mix. Instead they form three different layers.
The denser fluids sink to the bottom while less dense fluids rise to the top. Where other objects sit in the density
column depends on how dense the objects are.
Temperature can affect the density of fluids and solids. The strange thing about ice is that it is less dense than
water, so it floats in the oil level. However, cold water is denser than warm water. Try adding a few droplets of
colouring to half a cup of very hot water (ask an adult to help you) and add it to your density column. Does the
colouring mix with all the water or does the hot coloured water form another layer?
Ever wondered why you need detergent for washing up your dishes? Normally, oil and water don‟t mix together.
When you add soap or detergent it reduces the surface tension of water, allowing it to dissolve the oil. Adding a
few drops of detergent won‟t be enough to dissolve all the oil in your density column. However, you should be
able to see „breaks‟ in the layers where some of the oil dissolved in the water.
Turn a margarine container into a balloon-powered jet boat? It's easy.
WHAT YOU NEED
To do this experiment you will need to gather:
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a margarine container
a balloon
a straw
a rubber band
plasticine
scissors
something that will pierce the margarine container to make a hole big enough to fit a straw through.
W H A T T O DO
1. Find a clean, rectangular, margarine container and carefully make a hole in the centre of one of the
shorter sides about 1 cm from the bottom.
2. Cut a straw in half and insert one end into the neck of a balloon. Fix the balloon firmly to the straw with a
rubber band.
3. Push the straw through the hole in the marg container and seal it in place with plasticine. Weigh the back
of the marg container with more plasticine in the centre. Blow the balloon up through the straw and pinch
the end to keep the air inside.
4. Put the boat in the water, let go - and away she goes.
This is an example of Newton's third law of motion - every action has an opposite and equal reaction. The air
rushing out of the straw is the action, and the equal reaction is the push against the boat in the opposite direction.
Can you improve the design of your boat?
Who needs a beach when you can surf on balloons? Try this activity at home or at school.
WHAT YOU NEED
To do this experiment you will need to gather:
an adult assistant
balloons
an upside-down desk or some other flat-bottomed object that can survive you standing on it
a carpeted floor
a table, pole or wall you can use to help yourself balance.
W H A T T O DO
1. Check that there is nothing sharp on the desk or floor that could damage a balloon.
2. Half-inflate four balloons and tie them off.
3. Place the balloons under the corners of the desk.
4. Have your assistant hold the desk still. They shouldn't try to take the weight, just help keep it balanced.
Make sure they do not put any of their fingers under the desk - they might get squashed!
5. Carefully step up onto the desk. You can use another table or a pole to help you balance as you climb up.
Unless something sharp bursts them, the balloons should be able to support your weight.
If there are other people around, you could try testing to see how many people the balloons can support.
WHAT YOU NEED
To do this experiment you will need to gather:
two balloons
two plastic PET bottles (1.25 L softdrink bottles work well)
a metal skewer, large darning needle or a knife.
W H A T T O DO
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1. Ask an adult to make a small hole (less than one
centimetre across) in the bottom of one of the
bottles. Be very careful when you do this because PET
plastic is extremely strong.
2. Stretch the neck of a balloon across the opening of
each of the bottles. Gently push the balloons so they sit
inside the bottles.
blow the balloons up in the bottles. Which one is the
3. Try and
easiest to blow up?
4. Take the PET bottle with the hole in it and place your finger tightly over the hole. What happens when
you try and blow it up now?
5. Take the PET bottle with the hole in it and blow the balloon up inside it. At the end of your last breath,
place your finger over the hole and take your lips off the bottle. What happens to the balloon?
6. Gradually release the pressure of your finger. What happens to the balloon now?
W H A T ' S H AP P E N I NG
You probably found that you could blow up the balloon in the bottle with the hole in it. You wouldn't have had
much luck with the other one though. Don't worry! There is nothing wrong with your lungs. It's got to do with
space.
Air takes up space just like anything else. When you blew up the balloons in the bottles, you were trying to push
air into a limited space. There wasn't enough room for the air in the sealed bottle as well as the extra air you were
trying to blow into the balloon. And your lungs certainly don't have the power of an air compressor so you can't
blow much extra air into the balloon in the hole-less bottle.
You could blow up the balloon when the hole was uncovered because air escaped from the hole and made room
for all the extra air you blew into it. So you were blowing some air in the top but some was also escaping through
the hole.
You saw the reverse happening when you blew up the balloon in the bottle with the hole and then put your finger
over the hole. As you released the pressure of your finger, the elastic sides of the balloon forced the air out of the
balloon, returning it to its original size. So air was forced out the top but was replaced by air entering back
through the hole at the bottom.
WHAT YOU NEED
To do this experiment you will need:
a balloon
25 cm of cotton thread
a tap.
W H A T T O DO
1. Blow up the balloon and tie the end.
2. Tie the piece of thread to the end of the balloon.
3. Hang the balloon a few centimetres away from a stream of cold water rushing from a tap.
W H A T ' S H AP P E N I NG
You should see the balloon move towards the stream of water. If you hold the balloon with your fingers instead
of by the thread, you may be able to make the stream of water move towards the balloon (as in the photo above).
When you turned on the tap, the rushing stream of water started moving the air around it. Due to the fact that this
air was moving, it had a lower pressure than the surrounding still air.
Holding the balloon near the stream of water meant it had low pressure air on one side (the side near the water)
and higher pressure air on the other side. High pressure air always pushes towards low pressure air. The higher
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pressure air on the other side of the balloon pushed the balloon towards the stream of water. This is called the
Bernoulli Principle.
WHAT YOU NEED
To do this experiment you will need to gather:
a hard boiled egg (boiled for 15-20 minutes) that has been allowed to cool
a glass bottle or jar with an opening at the top a couple of millimetres smaller than the egg
some newspaper
matches or a lighter
a sink to do the activity on
an adult helper.
W H A T T O DO
1. Peel the shell off the hard boiled egg.
2. Place the pointy end of the egg in the neck of the glass bottle or jar.
3. Scrunch up a piece of paper and light it then lift the egg up and carefully (but quickly) put the burning
paper into the bottle and replace the egg.
W H A T ' S H AP P E N I NG
Thwump - the egg gets sucked into the bottle.
The burning paper causes the air inside the bottle to expand, pushing some of it out of the bottle. When the paper
goes out, the air cools and contracts. The air pressure outside the bottle is greater and the egg is 'pushed' into the
bottle.
To get the egg back out of the bottle, wash the ashes out of the bottle. Turn it upside down and position the egg
with the pointy end back in the opening. Take a deep breath and blow in. Continue to hold the bottle upside
down, wait and watch.
WHAT YOU NEED
What will happen when you drop it?
To do this experiment you will need:
four pieces of plywood
a balloon
a lead sinker
a needle
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rubber bands
tape
nails
a hammer.
W H A T T O DO
1. Put together a rectangular wooden frame.
2. Using elastic bands, suspend a lead sinker from the top of the inside of the frame so that the rubber bands
are stretched. Attach an upward facing needle to the sinker.
3. Inflate a balloon and stick it to the top of the frame so the needle is suspended below the balloon.
4. Try dropping the frame from a couple of metres high with someone there to catch it so your construction
isn't damaged when it hits the ground. What happens to the balloon?
W H A T ' S H AP P E N I NG
When an object falls the effects of gravity are cancelled out and an object experiences weightlessness. In this
case, the frame and the objects inside become weightless. However, if the lead sinker becomes weightless, the
elastic bands, which are stretched, will now pull the sinker up causing the needle to puncture the balloon.
E X P E R I M E N T 2 : DR O P C U P
Many strange things happen with falling objects due to the effects of gravity being cancelled out. What's not
happening in this experiment that you would expect to happen under normal circumstances?
It's best to do this experiment outside as it will make a mess.
WHAT YOU NEED
To do this experiment you will need:
a styrofoam cup
a pen or pencil
water.
W H A T T O DO
What a difference a drop makes!
1. Fill a styrofoam cup with water and put a hole in the bottom side of the cup with a pencil. As
you'd expect, water pours out (as in the cup on the left in the image).
2. Now drop the cup full of water. It's a good idea to have a bucket under the falling cup to prevent a mess
when it hits the ground.
W H A T ' S H AP P E N I NG
The water becomes weightless while the cup is falling and, for the duration of the fall, it no longer pours out of
the hole.
See if you can come up with your own falling demonstrations that might produce other interesting effects.
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WHAT YOU NEED
To do this experiment you will need:
a film canister
baking soda (sodium bicarbonate)
vinegar (any kind will work, but white vinegar is easiest to clean up)
an ice cream stick or teaspoon
a plate, saucer, tray or similar
eye protection (glasses, sun glasses or safety goggles)
an adult.
W H A T T O DO
1. Take the lid off the film canister. Before adding the ingredients, practise putting on the lid and placing it
upside down as described in step 5.
2. Put on your eye protection.
3. Pour a small amount of vinegar, about 5 millimetres deep, into the body of the canister.
4. Using the teaspoon or icecream stick, place enough baking soda to fill the recess in the lid.
5. Hold the body of the canister in one hand and the lid in the other. Quickly and firmly press the lid
completely on, place the canister lid down on the plate and stand back. Make sure your plate is on a level
surface. Your canister rocket will blast off seconds later. The exact timing will depend on the canister,
temperature, amount of ingredients and how tightly you packed the baking soda in.
6. Have a close look at the lid and bubbling ingredients left on the plate.
W H A T ' S H AP P E N I NG ?
When vinegar and baking soda mix together, there is a fast chemical reaction. There are several products of the
reaction, although it is the carbon dioxide gas (C0 2) that pops the lid off.
As more and more carbon dioxide is produced, the bits of carbon dioxide (called molecules) are squashed
together and begin to push, or apply a force, on all the inside surfaces of the canister, including the lid.
Pressure is defined as a force over an area. In this case, it's the force of the carbon dioxide pushing over the inside
area of the canister. As the carbon dioxide builds up, so does the pressure inside the canister. The pressure
quickly pops the lid off.
A good way to understand what is happening is to take a deep breath in, seal your lips and slowly breathe back
out into your mouth. Eventually your mouth cannot hold the pressure and your lips will unseal, letting some air
out. Caution: don't overdo this as you can hurt your eardrums.
The carbon dioxide gas pushes down on the lid, although as it is sitting on the plate it can't go anywhere when it
pops. The carbon dioxide is also pushing on the inside base of the canister (the top of your rocket) and this
pushes it into the air.
To do this experiment you will need
a balloon (not blown up)
a short piece of drinking straw
a long piece of string
sticky tape
two friends.
W H A T T O DO
1. Blow up the balloon and hold the neck to stop the air escaping.
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Cartoon of the jet balloon experiment
2. Ask your friends to hold either end of your string so the string is taut.
3. Thread the straw onto the string and tape it to the balloon so that one end of the straw points to the neck
of the balloon.
4. Hold the balloon at one end of the string and let go of it.
W H A T ' S H AP P E N I NG
The balloon should fly to the other end of the string as it deflates.
Many years ago, a scientist named Isaac Newton realised that when an object applies a force onto another object,
the other object pushes back with an equal force in the opposite direction.
When you let go of the balloon, the air is pushed out of the neck of the balloon. As it does, the air pushes on the
balloon with equal force in the opposite direction, so the balloon is pushed along the string. The air comes out of
the balloon faster than the balloon is pushed along, because the air is much lighter than the balloon.
All rockets work by using the same principle. In a rocket, fuel is burned in a combustion chamber, which is open
at one end. As the fuel burns, it produces hot gases, which rush out the open end of the chamber. Since the gases
are being pushed in one direction by the rocket, the rocket is pushed in the opposite direction with equal force.
WHAT YOU NEED
For this experiment, you will need:
a small soft-drink bottle with its label removed (one with straight sides works best)
a torch
milk
correction fluid (such as liquid paper) or paint
a very dark room (try to do the experiment when it is dark outside)
sink, bucket or jar
a thumbtack or safety pin
sticky tape
scissors
paper.
For this activity, we will need to make a thin, straight beam of light. Most torches produce a fairly wide beam, so
you may need to use the paper to cover most of the end so only a thin beam of light comes out. Try for a beam
with a width of one centimetre or less.
W H A T T O DO
There are two parts to this activity. The first part shows how light bounces underwater.
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The light beam is reflected back into the water.
1. Fill your bottle partway with water.
2. Add a drop of milk, to make it easier to see the path of the light through the water.
3. Place the bottle near the edge of a table in your dark room.
4. Hold the torch down fairly low and shine it up through the side of the bottle onto the bottom of the
water's surface. You should find the light travels up through the water, through the surface and into the
air.
5. Keep the beam of light aimed at the same point on the surface, but slowly lift the torch up so the angle
between the light and the water becomes smaller and smaller.
6. When the angle between the water and the beam of light becomes small enough, the light will not go
through the surface any more but will bounce off it, like it was a mirror.
The next part shows how to trap light in a stream of water.
1. With the thumbtack, make a small hole in the bottle, a couple of centimetres from the bottom. You might
find this easier if the bottle is filled with water so the sides don't bend when you push on them.
2. Empty the bottle, dry off the outside and paint around the hole with correction fluid or paint. Paint at
least one centimetre in each direction, and a couple of centimetres downwards. This ensures that the
beam of light only travels down the stream of water.
3. Fill the bottle with water until the water squirts out the hole in a steady stream. Make sure you have a
sink or bucket set up to catch the water.
4. Shine your torch at the hole from the other side of the bottle.
5. As the water comes out of the bottle, it will look clear until it starts to break up into drops. At that point,
you may see some light glittering on the drops. Hold your finger in the water stream above the point
where it breaks up. You should see a spot of light on your finger.
6. If you look closely, you should find that the point of light is actually below the level of the hole. The light
has stayed inside the stream of water as it bent down.
W H A T ' S H AP P E N I NG ?
Both of these activities rely on an effect called total internal reflection.
The beam of light stays inside the stream of water.
When light hits a boundary between two substances, like the surface of water, it often bends. This is called
refraction. In the case of water and air, light bends towards the surface of the water when it goes from water into
air.
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As the angle on the water side becomes smaller, the angle on the air side gets smaller even
faster. When the angle on the water side is just right, the angle on the air side would have to
be zero, so the light would be trying to go along the surface.
If the angle on the water side is any smaller, then instead of going through into the air, the
light bounces off the surface of the water. This is called total internal reflection. For the
surface between water and air, the critical angle is 41.5 degrees.
In this activity, the light stayed inside the stream of water because of total internal reflection.
To start with, the light and the water both come out of the hole horizontally. As the water
curves down, the light eventually hits the surface. Since the angle between the surface and the light is very slight,
the light bounces off.
As the water keeps bending, the light inside it keeps bouncing off the surface, until the water starts to break up.
The same effect happens inside other clear materials such as long thin strands of glass or plastic, even if the
strand curves or goes around in circles. This is called an optic fibre.
APPLICATIONS
Doctors can look inside a person's body using a bundle of optic fibres connected to a television camera outside
the body. This has lead to 'keyhole surgery', where doctors carry out complicated operations through small holes
in the skin, instead of having to make large incisions.
Optic fibres are also used to carry information, like telephone calls. By sending the information as carefully
controlled pulses of different coloured light, it is possible for a single fibre less than a millimetre wide to carry
thousands of phone calls.
Optic fibres are becoming more important as scientists and engineers are developing technology called photonics,
which is the study of ways to generate and harness light and other forms of radiant energy.
W H A T T O DO
1. Cut a circle from a piece of cardboard.
2. On one side draw a head with an apple on it.
3. On the other side of the cardboard, draw an arrow (or pick two other related pictures like a fish and a
fishbowl).
4. Use sticky tape to attach the circle onto a straw.
5. Roll the straw back and forth between the palms of your hands, while you look at the cardboard. What do
you see?
W H A T ' S H AP P E N I NG
Modern movies use technology to produce an optical illusion and fool our brains.
When you look at a picture, your eye and brain retain the image for a fraction of a second after it has gone. This
is called persistence of vision.
If you are shown more than ten pictures a second, your brain will merge the separate images into a series of
moving images.
Motion pictures show 24 still frames per second that give the illusion of smooth motion. The brightness of an
image also affects the length of time the image will remain in your brain.
WHAT YOU NEED
To do this activity you will need:
sunlight
a piece of card with a one millimetre wide slit cut into the middle
a straight-sided glass filled with water
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a sheet of white A4 paper.
W H A T T O DO
1. Fill a straight-sided glass with water and tape the card onto the side of the glass.
2. Place the white sheet of paper close to a window where sunlight is entering.
3. Stand the glass on the paper with the slit facing towards the Sun.
4. The sunlight should pass through the slit and split into its colour components as it enters the glass. The
colours should appear on the paper.
W H A T ' S H AP P E N I NG ?
White light is a mixture of many different colours. Sir Isaac Newton proved this more than 300 years ago when
he directed a beam of sunlight through a slit and prism in a darkened room in 1666.
The prism bent, or refracted, the white light so that it fanned out into a rainbow (spectrum) of colours.
Splitting light using prisms is known as spectroscopy. Each chemical element has a unique signature when its
light is split up.
Astronomers use spectroscopy to determine what planets and stars are made of by examining their light.
WHAT YOU NEED
To do this experiment you will need:
a balloon
a hair dryer.
W H A T T O DO
1. Blow up the balloon and tie it off.
2. Turn on the hair dryer and point it so the stream of air is blowing towards the ceiling.
3. Hold the balloon in the stream of air and then let go.
If you've never done this experiment before, you'd probably expect the balloon to float up and then fall to one
side. What actually happens is that the balloon hangs in the middle of the air stream.
Diagram of the 'staying up there' experiment
W H A T ' S H AP P E N I NG
The balloon hangs in the stream through a balance of forces. The downward pull of gravity is balanced by the
upward push of the air flow.
The balloon stays in the centre of the air stream because the fast moving air has a lower pressure than the
surrounding still air. If the balloon starts to move out of the air stream, the higher pressure of the surrounding air
pushes it back.
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Try tilting the hair dryer a bit. What happens now?
WHAT YOU NEED
To do this experiment you will need to gather:
an egg (uncooked)
sugar
hot water
two containers, such as glass jars.
W H A T T O DO
Pour about seven centimetres of water into each jar. Add a tablespoon of sugar to the water in one jar then stir
until it has dissolved. Repeat this until no more sugar will dissolve into the water. This is called a saturated
solution.
Carefully lower the egg into each jar. Does it float or sink?
W H A T ' S H AP P E N I NG
By adding sugar to water you increase the density of the water. Very sugary water is denser than an egg,
while fresh water is less dense than an egg. This means that the egg will float in the sugary water and sink in the
fresh water.
Try it yourself with a range of sugary solutions. Can you figure out a way of creating a solution which is sugary
at the bottom and fresh at the top? The egg would then 'float' midway.
WHAT YOU NEED
To do this experiment you will need the following items:
a glass bowl
a small glass
baby oil
a glass eye-dropper.
W H A T T O DO
1.
Place the small glass inside the glass bowl. Pour baby oil into the bowl until the oil covers the glass. The
refractive index of baby oil is very close to that of glass. The small glass should therefore appear
practically invisible.
2. Gently place the glass eyedropper into the small glass. It should appear visible because the eye-dropper
contains air - the refractive indices of air and glass are different.
3. Retrieve the eye-dropper, fill it with baby oil and place it back inside the glass. The eye-dropper should
become almost invisible because the air has been removed. When light passes from the oil into the glass
(and visa versa) it is only slightly bent.
Note: If you don't want to waste the baby oil, use the glass to pour it back into the bottle. Make sure you do this
over the bowl so it doesn't get everywhere.
W H A T ' S H AP P E N I NG
Could Harry Potter's invisibility cloak really exist? Well, science can begin to explain how Harry's cloak could
actually be invisible to the human eye!
For Harry's cloak to be invisible it needs to change the way light interacts with it. An object is only visible if it
reflects or bends (refracts) light that lands on its surface. If an object doesn't reflect or bend light it becomes
invisible!
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When light travels from one material to another it usually changes speed. This change in speed causes the light to
bend, and our eyes can detect the difference. For example, when light moves from the air into a raindrop and
back out again, the light changes its speed in the raindrop, and bends. When a straw is placed in a glass of water,
it may look 'broken' because the light reflecting off the straw in the water is refracted.
Each transparent material bends light by a particular amount depending on the material the light is travelling
from. We call the amount of bent light the 'refractive index'. For example, if the refractive index of water were
the same as air, light would not bend as it passes through. If light didn't bend as it passed through water we
wouldn't see raindrops falling. They would be invisible!
Therefore, the refractive index of Harry's cloak would have to be the same as air to make it appear invisible. But,
even if Harry's cloak were invisible, would Harry appear invisible too?
Harry's body would have a different refractive index compared to the air and his cloak. He would therefore
appear visible, the same way that you are visible behind a glass window. For the cloak to make Harry invisible,
Harry's body would also need to have the same refractive index as the air.
Interestingly, Harry's cloak would not be invisible if he wore it underwater. The refractive index of water is
different to air, and therefore different to Harry's cloak - making it visible.
Universal Indicator „Rainbow‟
Introduction
A long glass tube is filled with a neutral solution of Universal indicator.
Hydrochloric acid is added to one end and sodium hydroxide solution to the
other. The tube is inverted a few times to mix the solutions and the ‘rainbow’ of
Universal indicator colours appears.
Read our standard health & safety guidance
Lesson organisation
The demonstration itself takes only a few minutes. It provides a good attentiongrabbing lesson starter or lesson endpoint.
Apparatus and chemicals
Eye protection
For one demonstration, the teacher will need:
Glass tube. See note 1.
Bungs (rubber), 2, to fit the glass tube
Beaker (100 cm3)
Dropper pipettes, 3
Clamp stand, boss and clamp
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Distilled or deionised water
Hydrochloric acid, 0.1 mol dm-3 (Low hazard at this concentration)
Sodium hydroxide solution, 0.1 mol-3 (Irritant)
Universal indicator solution (Highly flammable). See note 2.
Technical notes
Hydrochloric acid (Low hazard). Refer to CLEAPSS Hazcard 47A.
Sodium hydroxide (Irritant). Refer to CLEAPSS Hazcard 91.
Universal indicator solution (Highly flammable). Refer to CLEAPSS Hazcard 32 and
40A, and CLEAPSS Recipe Card 36.
1 The glass tube needs to be about 60 cm long with an internal diameter of around
1 cm.
2 The concentrations of the solutions are not critical.
Procedure
SAFETY: wear eye protection throughout
a Add sufficient Universal indicator to about 60 cm3 of distilled or deionised water in
a beaker, to give a solution with a visible green colour.
b Ensure that one end of the glass tube is firmly stoppered with a rubber bung.
c Fill the tube to about 2 cm from the top with the Universal indicator solution. Then
clamp the tube vertically. It is important to leave a space above the liquid in the
tube so that there is an air bubble – this helps the mixing in step h.
d Add 3-4 drops of the hydrochloric acid solution. The top few centimetres of the
liquid should turn red.
e Stopper the upper end of the tube, remove it from the clamp, carefully invert it
and then clamp it vertically again.
f Remove what is now the top stopper. Add 3-4 drops of the sodium hydroxide
solution. The top few centimetres of the liquid should turn purple.
g Stopper the tube. Both ends of the tube should now be firmly stoppered.
h Remove the tube from the clamp and carefully invert it 2 or 3 times. The
movement of the air bubble will mix the contents and produce a „rainbow‟ in the
tube, showing all the colours of Universal indicator from red through orange, yellow,
green, blue and purple.
Burning money
Fireproof paper
a Put 2-3 g of potassium manganate(VII) in a small pile on the tin lid standing on
the heatproof mat. Make a small hollow in the centre of the pile.
b Pour about 1 cm3 of glycerol into the hollow in the pile of potassium
manganate(VII).
It is sometimes better if the glycerol is warmed just before use. After about 20
seconds (but beware – it can be much longer), the mixture starts to give off steam.
The glycerol in the mixture then ignites, burning with a bright, pinkish (lilac) flame
for a few seconds more, leaving a dark brown or black residue.
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Making glue from milk
A form of glue can be made from the protein, casein in milk. The casein is
separated from milk by coagulation and precipitation.
Read our standard health & safety guidance
Lesson organisation
This experiment should take no more than about 30 minutes. It can be done by
students in groups of two or three.
Apparatus and chemicals
Eye protection
Each group requires:
Beaker (250 cm3)
Glass stirring rod
Filter funnel and filter paper
Paper towel
Teaspoon
Conical flask (250 cm3)
Bunsen burner, tripod and gauze
Skimmed milk, 125 cm3
Distilled vinegar, 25 cm3. See note 1.
Sodium hydrogencarbonate, about a teaspoonful
Technical notes
1 Distilled vinegar is best because it is colourless. Other forms of vinegar can be
used. A dilute solution of ethanoic acid could also be used.
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Procedure
SAFETY: Wear eye protection
a Place about 125 cm3 of skimmed milk into the 250 cm3 beaker, and add about 25
cm3 of vinegar.
b Heat the beaker gently, with constant stirring, until small lumps begin to form.
c Remove the beaker from the heat, and continue to stir until no more lumps form.
d Allow the curds to settle. Decant off some of the liquid (known as whey). Filter off
the remainder into the conical flask using the funnel and filter paper.
e Use the paper towel to remove excess liquid from the curds in the filter paper.
f Transfer the curds to the empty beaker, add about 15 cm3 of water and stir.
g Add about half a teaspoonful of sodium hydrogen carbonate. Watch for bubbles of
gas. Then add a little more sodium hydrogen carbonate, until no more bubbles
appear.
h Stir the solid. You will find that it now has the consistency of glue and is very
viscous.
i Students could devise a way to test their glue. The teacher must check students'
plans before they start testing.
Teaching notes
Casein is the predominant protein found in fresh milk and cheese. In milk it exists in
the form of a soluble calcium salt.
In its acidic form, casein is precipitated by acids such as ethanoic acid (the
predominant acid in vinegar). In this experiment, calcium ethanoate is a by-product
of the initial souring process, and it is one of the components of the whey solution.
The insoluble casein which forms the curds has relatively little secondary or tertiary
structure. This means it cannot denature (change structure). It is relatively
hydrophobic, and this is why it is fairly insoluble in water.
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If appropriate, students may like to be reminded of Little Miss Muffet „who sat on a
tuffet, eating her curds and whey ....‟ Students should realise that they have
probably eaten curds and whey, because these are the lumps and the liquid in
cottage cheese. However, in cheese manufacture vinegar isn‟t the agent used to
precipitate out the casein; the enzyme „rennin‟ is used instead.
In addition to being consumed in milk, casein is used to manufacture adhesives,
binders, protective coatings, plastics (such as for knife handles and knitting
needles), fabrics, food additives, and many other products. It is commonly used by
bodybuilders as a slow-digesting source of amino acids.
Student questions
Here are some possible questions for students. (Answers in brackets.)
1 What do you think is the purpose of the vinegar in this experiment? (To convert
the casein into an insoluble form - the curds.)
2 Why is sodium hydrogen carbonate added? (To remove any excess acid.)
3 What is the gas given off when the sodium hydrogen carbonate is being added?
(Carbon dioxide - acids react with carbonates to form this gas.)
4 Use a search engine to find information about casein, which is present in milk.
What type of substance is casein? (Casein is a protein, or, more precisely, a
phosphoprotein.)
Health and Safety checked, September 2007
Web links
This gives general information on casein in milk
www.foodsci.uoguelph.ca/dairyedu/chem.html
Ammonium dichromate volcano
Ammonium dichromate (!), alcohol soaked wooden splint
Indicator Rainbow
Long glass tube, stoppered at both ends, stand and clamp, droppers. Universal
indicator solution 0.5-1M acid and base (HCl/NaOH).
Similar – u-tube with salt solution, universal indicator, copper electrodes, power
supply.
Wax/sand volcano
Beaker, wax, sand, water.
Syllabus Links:
Method:
Safety:
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Universal Indicator „Rainbow‟
Introduction
A long glass tube is filled with a neutral solution of Universal indicator.
Hydrochloric acid is added to one end and sodium hydroxide solution to the
other. The tube is inverted a few times to mix the solutions and the ‘rainbow’ of
Universal indicator colours appears.
Read our standard health & safety guidance
Lesson organisation
The demonstration itself takes only a few minutes. It provides a good attentiongrabbing lesson starter or lesson endpoint.
Apparatus and chemicals
Eye protection
For one demonstration, the teacher will need:
Glass tube. See note 1.
Bungs (rubber), 2, to fit the glass tube
Beaker (100 cm3)
Dropper pipettes, 3
Clamp stand, boss and clamp
Distilled or deionised water
Hydrochloric acid, 0.1 mol dm-3 (Low hazard at this concentration)
Sodium hydroxide solution, 0.1 mol-3 (Irritant)
Universal indicator solution (Highly flammable). See note 2.
Technical notes
Hydrochloric acid (Low hazard). Refer to CLEAPSS Hazcard 47A.
Sodium hydroxide (Irritant). Refer to CLEAPSS Hazcard 91.
Universal indicator solution (Highly flammable). Refer to CLEAPSS Hazcard 32 and
40A, and CLEAPSS Recipe Card 36.
1 The glass tube needs to be about 60 cm long with an internal diameter of around
1 cm.
2 The concentrations of the solutions are not critical.
Procedure
SAFETY: wear eye protection throughout
a Add sufficient Universal indicator to about 60 cm3 of distilled or deionised water in
a beaker, to give a solution with a visible green colour.
b Ensure that one end of the glass tube is firmly stoppered with a rubber bung.
c Fill the tube to about 2 cm from the top with the Universal indicator solution. Then
clamp the tube vertically. It is important to leave a space above the liquid in the
tube so that there is an air bubble – this helps the mixing in step h.
d Add 3-4 drops of the hydrochloric acid solution. The top few centimetres of the
liquid should turn red.
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e Stopper the upper end of the tube, remove it from the clamp, carefully invert it
and then clamp it vertically again.
f Remove what is now the top stopper. Add 3-4 drops of the sodium hydroxide
solution. The top few centimetres of the liquid should turn purple.
g Stopper the tube. Both ends of the tube should now be firmly stoppered.
h Remove the tube from the clamp and carefully invert it 2 or 3 times. The
movement of the air bubble will mix the contents and produce a „rainbow‟ in the
tube, showing all the colours of Universal indicator from red through orange, yellow,
green, blue and purple.
Burning money
Fireproof paper
a Put 2-3 g of potassium manganate(VII) in a small pile on the tin lid standing on
the heatproof mat. Make a small hollow in the centre of the pile.
b Pour about 1 cm3 of glycerol into the hollow in the pile of potassium
manganate(VII).
It is sometimes better if the glycerol is warmed just before use. After about 20
seconds (but beware – it can be much longer), the mixture starts to give off steam.
The glycerol in the mixture then ignites, burning with a bright, pinkish (lilac) flame
for a few seconds more, leaving a dark brown or black residue.
Making glue from milk
A form of glue can be made from the protein, casein in milk. The casein is
separated from milk by coagulation and precipitation.
Read our standard health & safety guidance
Lesson organisation
This experiment should take no more than about 30 minutes. It can be done by
students in groups of two or three.
Apparatus and chemicals
[email protected]
Eye protection
Each group requires:
Beaker (250 cm3)
Glass stirring rod
Filter funnel and filter paper
Paper towel
Teaspoon
Conical flask (250 cm3)
Bunsen burner, tripod and gauze
Skimmed milk, 125 cm3
Distilled vinegar, 25 cm3. See note 1.
Sodium hydrogencarbonate, about a teaspoonful
Technical notes
1 Distilled vinegar is best because it is colourless. Other forms of vinegar can be
used. A dilute solution of ethanoic acid could also be used.
Procedure
SAFETY: Wear eye protection
a Place about 125 cm3 of skimmed milk into the 250 cm3 beaker, and add about 25
cm3 of vinegar.
b Heat the beaker gently, with constant stirring, until small lumps begin to form.
c Remove the beaker from the heat, and continue to stir until no more lumps form.
d Allow the curds to settle. Decant off some of the liquid (known as whey). Filter off
the remainder into the conical flask using the funnel and filter paper.
e Use the paper towel to remove excess liquid from the curds in the filter paper.
f Transfer the curds to the empty beaker, add about 15 cm3 of water and stir.
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g Add about half a teaspoonful of sodium hydrogen carbonate. Watch for bubbles of
gas. Then add a little more sodium hydrogen carbonate, until no more bubbles
appear.
h Stir the solid. You will find that it now has the consistency of glue and is very
viscous.
i Students could devise a way to test their glue. The teacher must check students'
plans before they start testing.
Teaching notes
Casein is the predominant protein found in fresh milk and cheese. In milk it exists in
the form of a soluble calcium salt.
In its acidic form, casein is precipitated by acids such as ethanoic acid (the
predominant acid in vinegar). In this experiment, calcium ethanoate is a by-product
of the initial souring process, and it is one of the components of the whey solution.
The insoluble casein which forms the curds has relatively little secondary or tertiary
structure. This means it cannot denature (change structure). It is relatively
hydrophobic, and this is why it is fairly insoluble in water.
If appropriate, students may like to be reminded of Little Miss Muffet „who sat on a
tuffet, eating her curds and whey ....‟ Students should realise that they have
probably eaten curds and whey, because these are the lumps and the liquid in
cottage cheese. However, in cheese manufacture vinegar isn‟t the agent used to
precipitate out the casein; the enzyme „rennin‟ is used instead.
In addition to being consumed in milk, casein is used to manufacture adhesives,
binders, protective coatings, plastics (such as for knife handles and knitting
needles), fabrics, food additives, and many other products. It is commonly used by
bodybuilders as a slow-digesting source of amino acids.
Student questions
Here are some possible questions for students. (Answers in brackets.)
1 What do you think is the purpose of the vinegar in this experiment? (To convert
the casein into an insoluble form - the curds.)
2 Why is sodium hydrogen carbonate added? (To remove any excess acid.)
3 What is the gas given off when the sodium hydrogen carbonate is being added?
(Carbon dioxide - acids react with carbonates to form this gas.)
4 Use a search engine to find information about casein, which is present in milk.
What type of substance is casein? (Casein is a protein, or, more precisely, a
phosphoprotein.)
Health and Safety checked, September 2007
Web links
This gives general information on casein in milk
www.foodsci.uoguelph.ca/dairyedu/chem.html
[email protected]
Flame colours – a demonstration
This demonstration experiment can be used to show the flame colours given by alkali metal, alkaline
earth metal, and other metal, salts. This is a spectacular version of the „flame tests‟ experiment that can
be used with chemists and non-chemists alike.
It can be extended as an introduction to atomic spectra for post-16 students.
Read our standard health & safety guidance
Lesson organisation
This experiment must be done as a demonstration. It takes about ten minutes if all is prepared in advance.
Preparation includes making up the spray bottles and conducting a risk assessment.
Your employer's risk assessment must be customised by determining where to spray the flame to
guarantee the audience‟s safety. Use a fume cupboard unless you are sure of an alternative space.
Apparatus and chemicals
Eye protection
Access to fume cupboard (unless a safe alternative space is available)
Trigger pump operated spray bottles (see note 1)
Bunsen burner
Heat resistant mat(s)
Hand-held spectroscopes or diffraction gratings (optional)
Samples of the following metal salts (no more than 1 g of each) (see note 2):
Sodium chloride (Low hazard)
Potassium chloride (Low hazard) (see note 3)
Lithium chloride (Harmful) (see note 3)
Copper sulfate (Harmful, Danger to the environment).
Ethanol (Highly flammable), approx 10 cm3 for each metal salt.
or IDA (industrial denatured alcohol) (Highly flammable, Harmful)
Technical notes
Sodium chloride is Low hazard. Refer to CLEAPSS Hazcard 47B.
Potassium chloride is Low hazard. Refer to CLEAPSS Hazcard 47B.
Lithium chloride is Harmful. Refer to CLEAPSS Hazcard 47B
Copper sulfate is Harmful, Danger to the environment. Refer to CLEAPSS Hazcard 27C.
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Ethanol is Highly flammable. IDA (industrial denatured alcohol) is Highly flammable, Harmful. Refer
to CLEAPSS Hazcard 40A.
1 Spray bottles of the type used for products such as window cleaner should be used.
These piston-operated spray bottles should be emptied, cleaned thoroughly and finally rinsed with distilled
water. Ideally, one bottle is needed for each metal salt. Never use spray bottles with a rubber bulb - the
flame may flash back into the container.
2 The chlorides of metals are the best but other salts also work. Make a saturated solution of each salt in
about 10 cm3 ethanol. To do this, add the salt to the ethanol in small quantities, with stirring, until no more
will dissolve – often only a few mg of salt will be needed. Place each solution in a spray bottle and label
the bottle. The solutions can be retained for future use. They can be stored in the plastic bottles for several
weeks at least without apparent deterioration of the bottles.
3 Potassium iodide and lithium iodide can be used instead. As a general rule, chlorides are usually
suggested as they tend to be more volatile and more readily available. These two are in fact a little more
volatile than the chloride, and potassion iodide is certainly likely to be available (refer to CLEAPSS
Hazcard 47B). Other metal salts (e.g. those of calcium and barium) can also be used provided an
appropriate risk assessment is carried out. Barium chloride is toxic but gives a different colour (refer to
CLEAPSS Hazcard 10A), while calcium chloride (Irritant) and strontium chloride (Irritant) are different
again (refer to CLEAPSS Hazcard 19A).
Procedure
HEALTH & SAFETY: Carry out the whole experiment in a fume cupboard or an area you have
previously shown to be safe. Wear eye protection. Ensure that the spray can be safely directed away from
yourself and the audience.
a Darken the room if possible.
b Light the Bunsen and adjust it to give a non-luminous, roaring flame (air hole open).
c Conduct a preliminary spray in a safe direction away from the Bunsen flame.
Adjust the nozzles of the spray bottles to give a fine mist.
d Choose one spray bottle. Spray the solution into the flame in the direction you have rehearsed. Repeat
with the other bottles.
e A spectacular coloured flame or jet should be seen in each case. The colour of the flame depends on the
metal in the salt used.
f As an extension, students can view the flames through hand-held spectroscopes or diffraction gratings in
order to see the line spectrum of the element. (Diffraction gratings work better. A better way to produce a
steady source of light is to use discharge tubes from the Physics Department – with a suitable risk
assessment.)
Teaching notes
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The colours that should be seen are:
sodium – yellow-orange (typical „street lamp‟ yellow)
potassium – purple-pink, traditionally referred to as „lilac‟ (often contaminated with small amounts of
sodium)
lithium – crimson red
copper – green/blue
calcium – orange-red (probably the least spectacular)
barium – apple green
strontium – crimson
The electrons in the metal ions are excited to higher energy levels by the heat. When the electrons fall
back to lower energy levels, they emit light of various specific wavelengths (the atomic emission
spectrum). Certain bright lines in these spectra cause the characteristic flame colour.
The colour can be used to identify the metal or its compounds (eg sodium vapour in a street lamp). The
colours of fireworks are, of course, due to the presence of particular metal salts.
Health & Safety checked, June 2007
Teacher’s Instructions – Cannon Fire
For Demonstration Only
Make sure you have…
Crystallising dish
Hydrogen peroxide (H2O2, 100 Volume)
Potassium permanganate (Manganate (VII) KMnO4)
Ethanol
Spatula
Matches
Taper
2 x heatproof mats
Measuring cylinder
What to do…
1. Measure 20 ml ethanol, 5 cm3 hydrogen peroxide and 20 ml water into the crystallising dish on a
heatproof mat. Place a second heatproof mat to one side.
2. Light the solution with a taper
3. Scoop the end (tiny amount!) of a spatula of potassium permanganate and tip it into the
crystallising dish You should see an increase in the size of the flame and hear a popping sound
4. Extinguish the flame by placing the second heatproof mat on top of the crystallising dish
5. Wash everything up (solution can go down the sink).
What’s Happening?
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Potassium permanganate oxidises hydrogen peroxide to produce oxygen (NB. Contrary to popular belief,
the potassium permanganate is NOT a catalyst). Ethanol burns to give a transparent blue flame. When you
add the potassium permanganate, it reacts with the hydrogen peroxide to produce oxygen in small
“pockets”.
2KMnO4 + 3H2O2 2MnO2 + 2H2O + 3O2 + 2KOH
These pockets of oxygen increase the intensity of the reaction and you get the cannon fire noise as the
pockets of oxygen hit the flame.
If you look carefully when the flame erupts, you can sometimes see a violet colour. This is because there
is a metal in a flame – potassium. Potassium gives a violet flame colour.
�
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�
Supersaturated sodium ethanoate crystallisation
To prepare solution, add 160g of sodium ethanoate to 30ml distilled water in a clean, dry
250ml conical flask. Use distilled water to wash any loose crystals from side of flask into
solution.
Place flask on hotplate, heat until all crystals dissolved. Remove from heat and cover with
parafilm or equivalent. Allow to cool to room temperature (may take hours).
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Smoke Bombs
potassium nitrate sugar (sucrose)
water
fuse
paper or plastic cups
plastic spoon
waxed paper
Construct the Smoke Bombs
1. In a paper or plastic cup, mix 3 parts potassium nitrate with 2 parts sugar (e.g., 3 tablespoons
potassium nitrate and 2 tablespoons sugar).
2. Using your plastic spoon, stir in just enough water to make a thick paste. Continue stirring until the
ingredients are evenly mixed.
3. Set lumps of the mixture (~1 tablespoon each or a little less) onto the waxed paper. Insert a fuse
into each lump.
4. Allow the smoke bombs to set up for 1-2 days. The drying time will depend on temperature and
humidity. Warmer and drier is faster; cooler and damper will take longer. Keep the smoke bombs
away from excessive heat or flame. The smoke bombs will be like clay when they are ready, not
hard and solid.
5. Set a completed smoke bomb outdoors on a fireproof surface and light it.
Coloured Smoke Bomb Materials
60 g (3 tablespoons) potassium nitrate (sold as saltpeter in garden supply shops)
40 g (2 tablespoons) sugar
1 teaspoon baking soda
60 g (3 tablespoons) powdered organic dye (found in laundry sections of the store as well as craft
& hobby shops)
cardboard tube (best is an iced push-pop tube (eat the treat first), or you could use a toilet paper
roll or section of paper towel tube, or even a rolled/taped paper tube)
duct tape
pen or pencil
firework fuse (hardware, rocketry, construction, or hobby shops, or scavenge it from a firework)
cotton balls
saucepan
Make the Coloured Smoke Bomb Mixture
1. Mix 60 g potassium nitrate with 40 g sugar in a saucepan over low heat. It's a 3:2 ratio, so if you
don't have grams, use three large spoonfuls of potassium nitrate and two large spoonfuls of sugar
(3 tablespoons and 2 tablespoons, if you feel the need to be precise).
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2. The sugar will caramelise and brown. Stir the mixture continuously until it resembles smooth
peanut butter.
3. Remove the mixture from heat.
4. Stir in a spoonful of baking soda (rounded teaspoon is fine). The baking soda is added to slow
down the combustion when the smoke bomb is ignited.
5. Add three large spoonfuls (3 tablespoons) of powdered organic dye. Blue dye and orange dye are
said to produce better results than the other colors. Stir to mix well.
6. Construct the smoke bomb while the mixture is still hot and pliable.
Assemble the Smoke Bomb
1. Fill a cardboard tube with the warm smoke bomb mixture.
2. Push a pen or pencil down into the centre of the mix (doesn't have to be all the way to the bottom
but should be enough that the pen stands in the mixture). You could use a different shape, but the
cylinder works really well.
3. Let the mixture harden (about an hour).
4. Remove the pen.
5. Insert a firework fuse. Push pieces of cotton balls into the hole to tamp the fuse securely inside the
smoke bomb. Be sure there is fuse left outside of the tube so that you will be able to light your
smoke bomb.
6. Wrap the smoke bomb with duct tape. Cover the top and bottom of the tube, too, but leave the hole
area with the cotton and fuse uncovered.
7. Go outside and light your smoke bomb!
Many commercial smoke machines use 'fog juice' that consists of glycols, glycerine, and/or mineral oil,
with varying amounts of distilled water. The glycols are heated and forced into the atmosphere under
pressure to create a fog or haze. There are a variety of mixtures that may be used. See the reference bar to
the right of this article for Material Safety Data Sheets on some example types. Some homemade recipes
for fog juice are:
1. 15%-35% food grade glycerine to 1 quart distilled water
2. 125 ml glycerine to 1 liter distilled water
(glycerine creates a 'haze' at concentrations of 15% or less and more of a fog or smoke at
concentrations higher than 15%)
3. Unscented mineral oil (baby oil), with or without water
(I can't vouch for the safety of using mineral oil for fog juice)
4. 10% distilled water: 90% propylene glycol (dense fog)
40% distilled water: 60% propylene glycol (quick dissipating)
60% water: 40% propylene glycol (very quick dissipation)
5. 30% distilled water: 35% dipropylene glycol: 35% triethylene glycol (long-lasting fog)
6. 30% distilled water: 70% dipropylene glycol (dense fog)
The resulting smoke should not smell 'burnt'. If it does, likely causes are too high of an operating
temperature or too much glycerine/glycol/mineral oil in the mixture. The lower the percentage of organic,
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the less expensive the fog juice, but the fog will be lighter and will not last as long. Distilled water is only
necessary if a heat exchanger or other tubing is used in the system. Using a homemade fog mixture in a
commercial machine will almost certainly void the warranty, possibly damage the machine, and possibly
pose a fire and/or health hazard.
Important Points
This type of fog is heated and will rise or disperse at a higher level than dry ice or liquid nitrogen
fog. Coolers can be used if low-lying fog is desired.
Changing the mixture or conditions of dispersion of atomized glycols can result in many special
effects that are difficult to achieve with other simulated smokes.
Glycols can undergo heat denaturation into highly toxic substances, such as formaldehyde. This is
one of the major problems with homemade smoke machines - they may operate at a temperature
that is incompatible with the substances being used. Also, this is a danger with homemade fog
juice used in commercial machines.
Glycols, glycerine, and mineral oil can all leave an oily residue, resulting in slick or sometimes
slightly sticky surfaces. Be aware of the potential safety hazards, especially since the smoke may
limit visibility. Also, some people may experience skin irritation from exposure to glycol fog.
Some glycols are toxic and should not be used to create smoke. Ethylene glycol is poisonous.
Some glycols are sold as mixtures. Medical or pharmaceutical grade non-toxic glycols only should
be used in smoke machines. Do not use antifreeze to make a fog mixture. The ethylene glycol
types are poisonous and the propylene glycol types always contain undesirable impurities.
If water is used, it needs to be distilled water, since hard water deposits can damage the atomizer
apparatus.
Some of the chemicals that can be used for this type of smoke are flammable.
How to light a smoke bomb
The solid smoke bomb material is flammable and can be lit directly. You can light your smoke bomb
using a lighter, preferably one of the long-handled types used for barbeque grills. Only light your smoke
bomb in a well-ventilated area, on a surface that won't catch fire. The smoke bomb will burn vigorously
(more slowly with a higher percentage of sugar) with a purple flame.
Alternatively, you could place a short length of wick into the smoke bomb when you pour it, and then
light the wick.
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White Smoke Recipe
Potassium nitrate - 4 parts
Charcoal - 5 parts
Sulfur - 10 parts
Wood dust - 3 parts
Red Smoke Recipe
Potassium chlorate - 15%
para-nitroaniline red - 65%
Lactose - 20%
Green Smoke Recipe
Synthetic indigo - 26%
Auramine (yellow) - 15%
Potassium chlorate - 35%
Lactose - 26%
Elephant Toothpaste Materials
50-100 ml of 30% hydrogen peroxide (H2O2) solution
saturated potassium iodide (KI) solution
liquid dishwashing detergent
food coloring
500 mL graduated cylinder
splint (optional)
Safety
Wear disposable gloves and safety glasses. Oxygen is evolved in this reaction, so do not perform this
demonstration near an open flame. Also, the reaction is exothermic, producing a fair amount of heat, so do
not lean over the graduated cylinder when the solutions are mixed. Leave your gloves on following the
demonstration to aid with cleanup. The solution and foam may be rinsed down the drain with water.
Procedure
1. Put on gloves and safety glasses. The iodine from the reaction may stain surfaces so you might
want to cover your workspace with an open garbage bag or a layer of paper towels.
2. Pour ~50 mL of 30% hydrogen peroxide solution into the graduated cylinder.
3. Squirt in a little dishwashing detergent and swirl it around.
4. You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam
resemble striped toothpaste.
5. Add ~10 mL of potassium iodide solution. Do not lean over the cylinder when you do this, as the
reaction is very vigorous and you may get splashed or possibly burned by steam.
6. You may touch a glowing splint to the foam to to relight it, indicating the presence of oxygen.
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Elephant Toothpaste Chemistry
The overall equation for this reaction is:
2 H2O2(aq) --> 2 H2O(l) + O2(g)
However, the decomposition of the hydrogen peroxide into water and oxygen is catalzyed by the iodide
ion.
H2O2(aq) + I-(aq) --> OI-(aq) + H2O(l)
H2O2(aq) + OI-(aq) --> I-(aq) + H2O(l) + O2(g)
The dishwashing detergent captures the oxygen as bubbles. Food coloring can color the foam. The heat
from this exothermic reaction is such that the foam may steam. If the demonstration is performed using a
plastic bottle, you can expect slight distortion of the bottle from the heat.
One of the most spectacular chemistry demonstrations is also one of the simplest. It's the dehydration of
sugar (sucrose) with sulfuric acid. Basically, all you do to perform this demonstration is put ordinary table
sugar in a glass beaker and stir in some concentrated sulfuric acid (you can dampen the sugar with a small
volume of water before adding the sulfuric acid). The sulfuric acid removes water from the sugar in a
highly exothermic reaction, releasing heat, steam, and sulfur oxide fumes. Aside from the sulfurous odor,
the reaction smells a lot like caramel. The white sugar turns into a black carbonized tube that pushes itself
out of the beaker. Here's a nice youtube video for you, if you'd like to see what to expect.
What Happens
Sugar is a carbohydrate, so when you remove the water from the molecule, you're basically left with
elemental carbon. The dehydration reaction is a type of elimination reaction.
C12H22O11 (sugar) + H2SO4 (sulfuric acid) → 12 C (carbon) + 11 H2O (water) + mixture water and acid
Although the sugar is dehydrated, the water isn't 'lost' in the reaction. Some of it remains as a liquid in the
acid. Since the reaction is exothermic, much of the water is boiled off as steam.
Safety Precautions
If you do this demonstration, use proper safety precautions. Whenever you deal with concentrated sulfuric
acid, you should wear gloves, eye protection, and a lab coat. Consider the beaker a loss, since scraping
burnt sugar and carbon off of it isn't an easy task. It's preferable to perform the demonstration inside of a
fume hood.
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Look at the websites of the chemistry department at your local or nearest University – most do have a link
to school activities but, if not, do have a look at the widening participation (WP)of that University.
A good summary of different enrichment activities for in or outside the classroom can be found in the
STEMNET directory – hopefully this will be updated for the next academic year.
http://www.stemdirectories.org.uk/teachers_&_lecturers/stem_directories_print_copies.cfm
Some useful websites:
Spectroscopy – tutorials, videos etc for NMR, IR and MS
http://www.chem.ucl.ac.uk/schools/index.html
http://www.le.ac.uk/spectraschool/
http://www.rsc.org/education/teachers/learnnet/spectra/index.htm
http://www.chem.ualberta.ca/~iip/spectrotutorial/TblofCont.html
Interactive lab-primer (excellent resource developed by last year‟s RSC Teacher Fellows on lab
techniques (videos and animations) - http://www.rsc-teacher-fellows.net/index.htm
Theory and revision
http://www.chemguide.co.uk/
http://www.knockhardy.org.uk/sci.htm
http://chemincontext.eppg.com/chapter1/index.html
http://www.wwnorton.com/college/chemistry/gilbert/home.htm
http://www.docbrown.info/index.htm
http://www.bestchoice.net.nz/
http://www.chemcollective.org/
http://www.succeedingwithscience.com/labmouse/index.php (AQA specification)
http://science.uwe.ac.uk/ls/orgchem/ (resource on organic chemistry)
Useful site summarising the RSC publications and resources for teachers
http://www.rsc.org/images/PubCatalogue_tcm18-128260.pdf
Link that contains a list of useful resources with websites
http://www.rsc.org/education/teachers/learnnet/cflearnnet/resource_dets.cfm?subj=t
Chemistry resources: KS3, AS and A2 – (AQA specification): http://chemsheets.co.uk/
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A good resource for Chemistry, Biology and Maths but not free (look at the 30 day trial):
http://www.yteach.co.uk/
Some interesting articles and podcasts : http://www.thenakedscientists.com/HTML/articles/chemistry/
Chemistry diagrams: http://www.btinternet.com/~chemistry.diagrams/index.htm
PowerPoint presentations developed by teachers:
http://www.worldofteaching.com/chemistrypowerpoints.html
A teacher resource exchange for a range of subjects – a keyword search will take you to the chemistry
resources: http://www.tre.ngfl.gov.uk/server.php?request=cmVzb3VyY2UuZnVsbhZpZXc%
Careers in Science
http://www.noisemakers.org.uk/index.cfm;
http://www.futuremorph.org/;
http://www.icould.org.uk/Index.aspx
http://www.planet-science.com/nextsteps/start.html
Publication – Science Enhancement Programme (SEP) : http://www.sep.org.uk/
videos
http://www.science.tv/
http://www.periodicvideos.com/about.htm (videos on elements of the periodic table, Nottingham
University)
work/research experience and work based learning: Nuffield Science Bursaries and Engineering
Development trust:
http://www.etrust.org.uk/
http://www.nuffieldfoundation.org/go/grants/nsb/page_390.html
Chemistry podcasts on articles from Chemistry World and the elements (RSC):
http://www.rsc.org/chemistryworld/podcast/index.asp
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