Re: Money to burn?

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

On Sun, 27 Jun 1999 16:26:09 -0400 Paul McCrory <WmPMcCrory@AOL.COM>
writes:
> I'm trying to put together a short series of demos for a competition
> in a science centre in the UK.  My theme is heat capacity, and I hope to

> start with the water balloon heat capacity demo.  I would like to follow

> this by trying to set light to a £20 note.  I'm sure that I read
somewhere
> recently that if the note is tightly wrapped around a metal cylinder it
will
> not burn when a candle is held underneath it  (again due the high heat
capacity
> of the metal)?   Of course I can't find this reference anywhere now!
> Can anyone confirm that this demo is possible?
> Also, does anyone know any other dramatic demos based on heat
> capacity?

A classic demo is to immerse specimens of the same size of aluminum,
copper, iron, and lead into boiling water for a few minutes. Remove and
dry the specimens quickly and place them on a block of paraffin. As they
melt the paraffin, they will sink down a distance related to the heat
capacity of the metal. Some other heat demos that you might adapt for
your competition are listred below.

ADIABATIC HEATING. A considerable temperature increase occurs when a
rubber band is stretched. Hold a thick rubber band against your upper
lip and extend it quickly. Your lip can sense the increase in
temperature. Allow the rubber band to contract rapidly and note that it
suddenly becomes colder.

BOILING WITH ICE. Fill a flask two-thirds full of water and bring it to
a boil. Cork the flask and invert it taking care that the hot water does
not spill out.  Place an ice cube on bottom of flask. As the ice melts,
the water begin to boil again.  If the flask is corked with a one-hole
stopper with a glass tube extended almost to the bottom of the flask,
boiling can be effected by reducing the pressure of the entrapped air.
You can also run cold water over the flask.  Have the student feel the
flask temperature as the ice boils the water. of boiling water.

CONDENSATION OF WATER VAPOR. A simple cloud chamber can be made from a
gallon jug fitted with a one-hole stopper with a short piece of glass
tubing.  Blow into the jug through the glass tubing to increase
pressure.  Put finger over end of tube and pull stopper, suddenly
reducing the pressure.  No cloud is formed.  If some smoke is introduced
into the jug it provides nuclei about which water vapor condenses.
Repeat the performance and watch the clouds form in the jug.
stationary.

CRUSHED CAN. The force of normal external air pressure is sufficient to
collapse a rectangular varnish can.  In a clean can place a few
tablespoons of water and bring it to a boil to expel the air with the
water vapor.  Close the cap tightly as soon as water boils vigorously.
Cool the can by dashing cold water on it.  ... two comments:  You don't
need to run cold water over the can.  Be sure to stopper it very soon
after you remove the source of heat.  If you don't, the reverse effect
happens.

DIMPLES AND PIMPLES. Heat a spot on a cold light bulb with a blow torch
and a dimple will form in the glass.  Light the bulb and again heat a
spot
until a pimple forms.

FLAME DISCHARGE. Ionization in a flame can be shown by holding a lighted
match near a charged electroscope.  Charged pith balls or balloons lose
their charge rapidly when a flame is brought near.

HEAT TREATMENT. The effect of heat treatment and tempering of metals can
be demonstrated by heating bobby pins to redness in a Bunsen flame. Dip
one heated pin in cold water to chill.  Allow the other pin to cool
slowly.  Compare these pins with one that has not been heated by bending
each one.

HOT DOG WHISTLE. Tune two metal dog whistles to unison or absence of
beats. Heat one whistle with flame.  Beats reappear as pitch of heated
whistle rises.  (please don't burn your lips!)

HOT ROD BALANCE. Drill a brass rod for a screw in one end.  Insert screw
about half way.  Balance rod at its center on a pivot.  Throw off balance
by moving small screw on one end.  Heat on end of rod and it will come to
balance again.

MATCH DISCHARGE. Rubber bands or strips can be tied together in bundles
and charged by stroking with fur or by other means.  A lighted match near
the repelling strands will cause them to collapse.

PAPER KETTLE. Boil water in a paper cup.  The paper will not burn until
the water has boiled away.

POURING CARBON DIOXIDE. Construct a series three 5-cm steps that will
fit into a wide mouth jar. Set a lighted candle on each step. Slowly pour
carbon dioxide gas from an open container into the jar. Carbon dioxide
is heavier than air. As it settles it extinguishes the candles one by one
starting with the candle at the lowest level. There are many ways to
generate carbon dioxide. Try mixing some vinegar with bicarbonate of
soda.

RATE OF HEAT CONDUCTION. Three students each holding a rod of a
different substance in a flame, will demonstrate the difference in
conductivity of heat by their object from the flame.  Use about the same
sized rods of iron, aluminum, glass, copper.


SINGING FLAME VARIATION.  Hold a four foot 1-1/2 inch glass tube
vertical. Insert in the bottom end at a predetermined resonance point
a heavy disc of wire gauze.  Heat the wire gauze with burner, then remove
flame and hear a phenomenon.

SINGING TUBES. A straight metal blow pipe connected to a gas supply is
fixed in an upright position on the demonstration desk and lighted.  A
thirty to sixty centimeter glass tube of large diameter is lowered over

THUNDER BUBBLES. Prepare a soap bubble solution in a shallow dish or
pan.  Fill a balloon or beach ball with a 2 to 1 mixture of hydrogen and
oxygen. Using a small nozzle delivery tube, blow the gas mixture from
the balloon through the soap solution to produce copious bubbles.  Pick
up handful of bubbles and hold them far out in front of you. Ignite the
bubbles with a match.  The explosion will not be felt by you. However,
someone standing too close to the bubbles may have an ear injured. ....
sound is indeed intense.  Try this in a long hall and get good
reverberations.

WOOD'S METAL. Carve a spoon mold in wood and fill with molten Wood's
metal. The spoon will melt in hot water, coffee, or tea.  Save the mold
to recast the spoon as part of the demonstration.

Herb Gottlieb from New York City
(Where we use dollar bills because 20 pound notes are too heavy to carry)