Liquid Nitrogen Demonstrations
Safety Notes & Concerns
Liquid nitrogen is a dangerous material. The following is an
excerpt from the Air
Products Nitrogen Material Safety Data
he entire contents of a 10 Liter dewar being spilled in a
274 square foot room with an 8 foot ceiling
would reduce oxygen levels
below the 19.5% level where Air
Products recommends the use of a
respirator. Since many
rooms are larger than this, suffocation does not
a major danger. When tran
sporting the liquid in a car,
it is probably a good idea to open a window.
The possibility of freeze burns represents a much more
serious danger and is
therefore our first concern. This does
not mean that the demonstration itself is
you must be careful
. Dangers include:
Nitrogen can spatter (possibly in eyes) while being
Flying chunks of frozen objects could cause eye
Children (being curious) will want to reach out and
touch nitrogen or other cold
above, contact with nitrogen can cause tissue damage,
and this must be
Therefore specific safety precautions should include:
dults must stress to children the importance of not
touching frozen objects
goggles whenever pouring or dumping nitrogen.
Nitrogen can spatter into the eyes, and potentially
blinding pieces of frozen
things can fly around when we
Use a glove and / or tongs to handle any object going
into or out of nitrogen and
to carry th
(more) Liquid Nitrogen Demonstrations
Safety Notes & Concerns
dults should familiarize themselves with the following first
(excerpted from the Air Products Nitrogen
Material Safety Data Sheet) for
cryogenic freeze bu
in case the worst happens:
If cryogenic liquid or cold
boil off contacts a
worker's skin or eyes, frozen tissues should be
flooded or soaked
with tepid water (105
DO NOT USE HOT WATER
. Cryogenic burns
which result in blistering or
deeper tissue freezing
should be seen promptly by a
Remember to stress the importance of not touching liquid
See also Liquid Nitrogen Safetygram (in pdf format
below) from Air Products
and Chemicals, Inc.
the Liquid Nitrogen Safetygram above requires Adobe
is available for free download.
Download Adobe Acrobat Reader
in’s and out’s
First of all...liquid nitrogen is not a toy! Be certain to read
prior to its use and never never never allow children to
play with this!!! With that
being said, here’s the details...
Nitrogen is the major component of our air (79%). Even though
nitrogen is a gas at
room temperature, it is possi
ble to contain it as a
liquid if its temperature can be
196°C. any object (solid,liquid or gas) that comes in contact with liquid
nitrogen that is above
erature will cause it to boil!
Liquid nitrogen is stored in a dewar flask which i
s like a well
bottle. Never use a thermos bottle to store liquid nitrogen!
The dewar allows the
nitrogen gas to escape. If the gas is not
allowed a chance to escape, it
the flask to explode!
Where do you get liquid nitrogen? Yo
u may try the following
A local college or university. Make a contact with their chemistry
department; this may prove used for many other things and ideas as
A high school in the area may have a Dewar flask which you can share.
industry such as oil companies, welders or welding suppliers, food
companies, meat packers that use freeze drying, frozen food
distributors, research labs, steel or metal processing
products companies, airports, etc...
hospital or dermatologist
Be safe...wear goggles and gloves at
imes...respect the nitrogen!
The Boiling Tea Kettle
The boiling tea kettle is a simple but effective demonstration.
pour some nitrogen into
a whistling tea kettle and put the
on. The kettle will instantly begin to whistle and
"steam" will be visible
shooting out of the kettle. At this point the tea kettle looks and acts
like the kind that kids are used to seeing when water has been
heated to a boil. The nitrogen i
boiling just like water would when
heated. What has heated the nitrogen to boiling? The room
temperature kettle! If your group is quiet and you remove the lid or
the whistle from the kettle
you can hear the nitrogen boil.
In a matter of moments after th
e nitrogen has been added to the
kettle frost will begin to
accumulate on the side of the kettle. Since
the frost gives the kettle a white coating, using a
works best. After the nitrogen has left the kettle the frost will melt
ter from the air will condense on the kettle and the
kettle will be well coated with
moisture. So be sure to leave the kettle
in a visible place while doing something else to allow
time for the
frost to melt. Often a student will notice the change.
Because liquid nitrogen is so very cold, things that are normally soft
are changed in surprising
and amusing ways. Blu
Tack, normally like
putty, can be shaped by hand into the shape of nails,
which when put
into liquid nitrogen go hard (as nails)
and can then be hammered into
(well, if the wall is fairly soft). Of course, liquid nitrogen
soon evaporates and the nails warm up,
and nails made of Blu
turn back into ordinary soft Blu
Tack, leaving a situation which seems
to other people
IMPOSSIBLE! How has someone made a nail of soft Blu
Tack and nailed it into the wall?
This is a very popular one. Pour some liquid nitrogen into the ice chest.
With gloves begin taking
balloons and putting them into the ice
As they get down into the nitrogen it is best to use
tongs to push
them all the way down.
As the nitrogen cools the air in the balloons the air
down their movement and the balloon begins to shrink. Many kids will
the air ha
s left the balloon. As you begin to fill the ice
chest with balloons the first ones in will
shrink but the next layer or
so may need to have nitrogen poured over them. Be careful, if the
balloons are sticking up over the top of the ice chest some of the
ured nitrogen will spill
outside the chest. So it is best to add more
nitrogen before the balloons begin to pile up.
Once you have added enough balloons to the chest you can begin to
take them out. Only use
tongs to remove the balloons. The
balloon will b
egin to re
inflate immediately as you take it out
ice chest and moments after you have pulled out a balloon it is
completely safe to touch
and shortly after looks and behaves like a
Repeated freeze/thaw combinations
will be more tha
n most balloons
can handle and some will pop on the re
Ping Pong Ball Spinner
Before doing the demo get a ping pong ball. The ones with the
patterns on them work best for this. If you only have white
balls use a marker to add
some colors or pattern to
one. Use a
straight pin to poke a tangential hole in the ping
Use tongs to submerse the ball in the nitrogen (it will want to
Hold it under for 30 seconds or so. During this time nitrogen is going
into the ho
Use the tongs to remove the ball and place it on to a table (it may
help to have
something to contain the ball and keep it from rolling
away). The nitrogen in the ball should heat
up and convert to a gas.
This expands and is forced out of
the hole. Because the hole was poked
on a tangent as the gas rushes outward it causes the ball to spin
usually at a high rate of
speed. Occasionally the ball needs to be "jump
started." You can do this be briefly and gently
touching the palm of
d to the top of the ball. This provides some additional heat to
get the ball rolling or rather spinning. This works just like a rocket
and occasionally the ball will
be lifted into the air by the rocket
action (if the hole ends up on the bottom).
Ice Cream with Liquid Nitrogen
Mix together the following ingredients:
75 grams sugar
3 ml vanilla
Blend all of these ingredients together to make a smooth mixture.
Place this blended mixture
into a metal bowl and add between 750
1000 mL of liquid nitrogen slowly while constantly
stirring with a
wooden spoon until the desired consistence has been achieved. Do not
more liquid nitrogen then or the iced cream wil
the ice cream melts, just add a
little more liquid nitrogen and stir!
The liquid nitrogen absorbed the heat from the blended
mixture. As this happened, the liquid nitrogen boiled off
taking the heat into the atmosphere
and away from the
cream! Remember...liquid nitrogen boils at
Celsius (and room
temperature is normally around 25
Racquetball in Liquid Nitrogen
Warnings: See warnings for liquid nitrogen. When the racquetball
shatters, pieces may travel a
g distance. Be sure to throw it up in a
safe place. Make sure that members of the audience do
not pick up
broken pieces of the racquetball. Always use glove to handle the
racquetball after it
has been in the liquid nitrogen.
The racquetball is a solid, bu
t the bonds are loose enough for the ball
to flex and bounce. When
the ball is made very cold, the bonds are
much tighter; therefore, when the ball hits the floor,
flexing and absorbing the force, the ball shatters.
The Physics: There are many
different kinds of bonds that hold
molecules together. The
stronger of these bonds are what hold solids
together. However, there are different levels of
bonds. Obviously, the
bonds inside of steel are stronger than the ones inside a racquetball.
in a racquetball allow it to flex. When a racquetball is
dropped under the influence of
gravity, it gains some kinetic energy.
Under normal conditions, this energy is absorbed by the
or flexing, of the racquetball when it comes in contact wi
racquetball then returns to its original shape returning the
energy back to kinetic energy. This
is what causes it to bounce. When
the racquetball is made very cold, the bonds become much
and the racquetball lo
ses its flexibility
. Because the ball can no
longer deform to
absorb the energy, the energy of ball act directly
on the bonds; thus, breaking them.
Okay… What about the FIRE demos? Well, first you
need to understand a few things…
The rate of a chemical reaction can be sped
up by increasing the
Surface area, Temperature
In this chapter you are going to look at a very fast reaction between
oxygen and a
. A fuel is matter that gives off energy when it
burns. You have learned about a fuel in
the last chapter
Burning wood is an exothermic reaction because it releases heat energy!
Other fuels include oils and gasoline!
The very fast chemical reaction that
takes place between oxygen and a fuel
is known as
s caused by combustion between
these two reactants!
esides oxygen and a fuel, what else do
all chemical reactions need? That’s
that is needed
to create fire is in the form of heat.
This heat can come from a lot of different places. A match, an electric
shun”; heat from two objects rubbing
together) are three common forms of heat! All of these things c
provide the activation energy needed to start a fire.
Once the activation energy starts to pull apart the atoms
inside the reactants, a fire will continue to burn as long as
there is fuel and oxygen.
Most of you have watched someone start a wood fire be
fore. Did the
wood burst into flames as soon as a match was brought close to it? Of
course not! It takes a little time for the wood to absorb enough heat
energy to start splitting apart its molecules.
Here is the chemical equation for
e of wood:
(There are a lot of atoms inside one molecule of wood, huh?)
Once you add enough heat to wood it turns the wood black and starts to
smoke, right? If you keep adding just enough heat to the wood to turn
it completely black, it will stop smoki
ng and form...
That’s right! The
you use to make BBQ is really
just wood that has been
heated up so much that it
does not have any more smoke
to give off! That is why a
charcoal fire does not give off
a lot of smoke!
But what would happen
if you heated up that charred wood/charcoal a little
In order to answer that question, we have to look at the smoke (CH
we have created along with the charcoal (C
When smoke gets heated, its atoms start to split apar
t and begin to
react with the oxygen in our air! Here is the chemical formula...
When smoke is heated, it reacts with oxygen to form water, carbon
This heat helps to keep the smoke reacting with the oxygen to produce
heat! And you should know by now that the rate of a
chemical reaction can be increased if
the temperature of the reactants!
So... are you saying the smoke
is the real fuel during
combustion? Yes it is!
The carbon in the charred wood can
also react with the oxygen in the
air. But this is a much slower reaction. It still can produce a lot of
which is why we use it in our BBQ grills! That is why the charcoal
will turn bright orange after it is done burning for awhile. When they
rn this color, the carbon inside the charcoal is reacting very well with
oxygen and is very hot! But since it is a slower reaction, it sends off a
lot of heat over a long time. This is very helpful when you are using
charcoal to cook your food!
compounds can be broken down to produce a lot of heat
during combustion. As you know, not everything in the world will burn.
For example, you cannot boil water and watch the steam burst into
Although it would be really cool!
The compounds tha
t go through combustion very well contain carbon and
hydrogen. Compounds with these two elements can be broken apart and
mixed together very easily with oxygen to form the products of
combustion (carbon dioxide
and water) very easily!
Gasoline burns very
because it is a
, which is a
compound made with only
carbon and hydrogen atoms.
Because of the dangers associated with the fire
demos, I have a small problem in writing them
all down. This is not to keep any information
from you, bu
t they can be a little dangerous and
should not be performed by any children. If
you are interested in obtaining a detailed list of
the fire demos, email me at
and I will be happy to
send you th
e links to these activities!
Be safe and enjoy!