May I ask you about the experiment which is proposed on the Donald
Simanek's web site? The text goes like this:
VARIABLE DENSITY. Moth
balls rolled in sodium bicarbonate and put into a cylinder of very dilute
hydrochloric acid will rise and fall with regularity. [HG]
I
didn't have time to try the experiment yet, but it sounds interesting. Does it
has to do with the small bubbles that are formed on the surface of the moth
ball due to the chemical reaction between the sodium bicarbonate and acid? I
suppose the bubbles will grow until they reach a certain size (ball goes up)
and then they will leave the ball (ball goes down).
Looking
forward to receive your answer
Best regards
Gorazd
Herbert H
Gottlieb wrote:
Dear Gorazd,
It was a pleasure to receive your e-mail with the attachment of your
"Water-Drop Projector" article. I do not recall seeing this article
before. Perhaps the February 2001 copy of TPT arrived when I was out of
the country and I missed that particular issue. Your idea is especially
good for use with a small group of students as a laboratory exercise in
Biology or Physics classes.
Perhaps you are unacquainted with an older version of a water-drop
microscope.
To make one:
1. Cut a 2 cm X 6 cm metal rectangle from a discarded can of soup or
other food.
2. Using a small blunt instrument, such as the back of a ball-point pen,
press an indentation, about the size of a water drop, near one end of the
metal rectangle.
3. In the center of the indentation, drill a small hole (approximately
1-2 mm diameter).
4. Fold the metal in half (with the aid of a ball point pen) under itscenter making sure that the end with the indentation remains visible on
the upper section of the fold.
5. Fill the indentation with water. It should form a drop with a curved
upper surface due to the surface tension of the water. For the same
reason, the water will not leak through the hole at the bottom of the
drop.
6. Look though the water drop at microscopic specimens placed below.
Because the surface of the water drop is curved the specimen will appear
to be magnified.
If the specimen is out of focus, try adjusting the distance to the
specimen by pressing the halves of the bent metal closer together.
IT REALLY WORKS !
hERB
On Sun, 10 Feb 2002 19:01:16 +0100 Gorazd Planinsic
<gorazd@fiz.uni-lj.si> writes:
Dear Mr. Gottlieb!
I am sending you the description of a simple experiment that may fit
into your collection of experiments with lasers (published in TPT
last
year). I am teaching Didactics of Physics at Phys. Dept. University
of
Ljubljana + working at Slovenian Science center as exhibit
director.
Best regards
Gorazd Planinsic
Phys.Dept.
University of Ljubljana
Jadranska 19
1000 Ljubljana, SLOVENIA
Herb Gottlieb from New York City
(Where it's nice to live but I wouldn't
want to be a tourist here)
herbgottlieb@juno.com