SCIENCE
IN THE CLASSROOM
(or
out of it)
August
= Pyromania
Please
note that these experiments should be done under the supervision of a responsible
adult
1. HOT AIR BALLOONS
Hot air balloons are enjoyed by students
at all levels and can be very
exciting entertainment as well as an educational activity.
requirements:
Some small aluminium (Aluminum) pie containers or other light non-flammable,
shallow containers. Plenty of light string. Large, lightweight garbage
bags.Matches
Methylated
spirits or denatured alcohol. Some newspapers. Very light wire.
method:
If
there is danger of fire or interference with property or powerlines then
perform this experiment indoors in a gymnasium. For teams or individual
students.
Using
string or the light wire attach the garbage bag to the pie dish. You may
need to stiffen the mouth of the bag using wire. Pour a small quantity
(2 or 3 mL) of Meths into the pie dish and light the fuel. As the hot gases
of combustion and heated air rise they fill the garbage bag which then
floats to the ceiling.
danger
- sometimes the meths spills out and little pools of flame spatter onto
the floor. This adds to the excitement and gives the spectators something
to do. They move quickly to extinguish spills using wads of newspaper.
It is of course advisable not to stand underneath the air balloons because
of this danger. If you are nervous have a fire extinguisher handy. If string
is used to attach the pie dish gondola the string can catch fire. The plastic
bag is apt to suffer if the attaching cords are too short or too much fuel
is added.
assessment
You
can run a competition to see which balloon rises the fastest, obtains the
greatest height or remains aloft for the greatest time. With appropriate
additional equipment you can measure velocity and altitude. Balloons which
lose fuel or catch fire do not fare well and should be disqualified anyway.
Considerable
discussion can be held about pressure and density; why hot-air balloons
rise; differences in fuels or methods of generating hot air, Design
and manufacturing skills can be tested and the effect of various
different fuel mixtures examined.
2. hydrogen
balloons
hydrogen
balloons are great excitement, especially when they are exploded.
equipment:
Aluminium
(Aluminum) powder, conc. NaOH (Sodium hydroxide, Caustic Soda) solution.
A sturdy wine bottle, A supply of party balloons and plastic bags. A candle
on a long pole.
Method
Keep
spectators at a safe distance (3m) and place the bottle behind a safety
screen in case it shatters. (Select a bottle without cracks or flaws).
Place a SMALL quantity
of the metal powder in the bottom of the wine bottle ( a champagne bottle
is good) and add conc Sodium hydroxide. Start with very small quantities
until you have built up confidence and experience. The reaction will produce
hydrogen gas releasing a considerable amount of heat. Place a party balloon
over the mouth of the bottle to capture the hydrogen gas.
When
sufficient Hydrogen has accumulated ignite it (away from the generator
bottle) by applying your lit "extend-a-candle" to the balloon. The
BOOM is outrageous. Size of balloon according to courage, presence of articles
liable to shattering and likelihood of law suits.
assessment
If
you do not wish to explode your balloon you can measure load carrying capacity,
altitude and velocity. Discuss lighter than air gases and the disasters
with hydrogen filled dirigibles eg R101. lead into experiments with helium.
discuss the chemistry of alumin(i)um, amphoteric elements. Use pressure
sensors or sound measuring devices to record the bang.
3.
the thermite reaction
This
is a reaction which has been used to weld rails.The laboratory manager
and myself have not tried it. It is our next project. Visit this
site again later to check progress
