Thermal Expansion of Stuff: Gases & Liquids
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### Lecture Description

Some strange and uncommon things occur in these adventures. For example: how can a gas which is HOT feel COLD? Let's look at some of these unusual things.

A. Here is an ordinary automobile tire - inflated. We agree that
the atmosphere is hot - the ground is hot - the tire is hot -
the air in the tire is hot. Now we depress the valve stem and out
comes some HOT air. But how does it feel? IT FEELS COLD!
IT IS COLD! That is - its temperature is lower the instant it
emerges.
B. There is a simpler demonstration of this strange business: The air
in my lungs is HOT. I now blow out some of this air from my
mouth. With my mouth wide open the air coming out IS HOT.
With my lips pursed as if to blow a whistle the air comes out
COLD! So - I am a strange creature: I can blow both hot and
cold!

C. Consider a CO2 fire extinguisher. We release the gas. The temperature drops so low that we get "CO2 snow".

D. We have a device which might well be called a SPUTNIK! It is
like a Hero's engine. A CO2 cartridge is lodged in a chamber -
the cartridge is pricked - the gas emerges - the Laws of Newton
play their proper role and the arm rotates. The gas comes out this—
a-way — the chamber goes that-a-way! Our interest here is this:
it is so cold that the water vapor in the room has condensed on it
and there is "frost" on the cartridge.

E. A cast-iron "bomb" is filled with water. ... filled completely with
the occluded gases first gotten rid of. We place this vessel in a
tub - a pail - of ice water. The water IN the chamber freezes.
The forces of expansion are tremendous and the "bomb" is shattered.
Dangerous to do! And we encounter this strange property of water:
that it expands when it freezes.

The forces arising in the expansion of a gas can be nicely shown with an Earth-bound Rocket. A steel pipe is tightly closed at one end. The pipe is filled with solid CO2 - "dry ice". The open end of the chamber is stoppered up. The CO2 goes into gas. The pressure increases. Out pops the stopper.

G. The Galilean Thermometer is an enchanting historical piece. A glass vessel of spherical shape has a one-hole stopper fitted to it with a glass tube. The vessel is held in a clamp upside down with the open end of the glass tube in a beaker of colored water. The air in the spherical vessel is cooled - say with ice put on it. The liquid in the lower beaker "climbs" up into the spherical chamber. If now with the column of liquid high in the tube the spherical vessel is warmed - as by placing the hand on it - the liquid is driven down. Here is an example of a higher column - a longer column - meaning a LOWER temperature! Nor must we forget the role that pressure plays in this demonstration. Galileo's thermo-meter was really a pressure-meter!

### Course Description

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.

This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.