MORE EXPERIMENTS
TIPS AND DODGES FOR THE WINTER EVENINGS
THE REFRACTORY CORK
A VERY interesting and amusing experiment may be performed with a bottle
and a cork.
Take a cork of a diameter less than the internal diameter of the neck of
the bottle you propose using, and ask a friend to make it enter the
bottle by blowing upon it.
At first sight this seems a very easy task, and your friend at once
proceeds to blow strongly upon the cork. This, however, instead of
making the cork enter the bottle, causes it to fly out.
Again your friend tries to overcome the troublesome cork, on the next
occasion by blowing very gently, but again it flies out (Fig. 1).
The explanation of this is as follows:--
In blowing upon the cork, a certain amount of air at the same time
enters the bottle, the air in which becomes so compressed that it
rapidly ejects the cork. There are, however, three ways in which the
refractory cork may be overcome.
[Illustration: FIG. 1.--The refractory cork.]
Since you know that by blowing on the cork it is at once ejected, try to
achieve success by performing the contrary action--that is, by
withdrawing some of the air from the bottle.
Indeed, the experiment will prove to you that, by so doing, you create
in the bottle a partial vacuum, and as soon as your mouth leaves the
neck of the bottle air enters it owing to atmospheric pressure. This
incoming current of air pulls with it the cork, which at once slides
into the aperture.
The same result may also be achieved by first warming the bottle, when,
owing to the expansion of the air, a part of it is expelled. Directly
the air inside the bottle cools, a vacuum is created, and a current of
air from without enters. If you add to this current of air by blowing
air from your mouth, you will find this quite sufficient to cause the
cork to enter the bottle. Then, again, having a straw or a pipe-stem
handy, all you have to do is to blow through the tube, directing the air
exactly on the base of the cork, which will once again enter the
aperture.
Whichever of these means is adopted, you must always take the precaution
of seeing that the bottle is perfectly dry. It should be wiped every
time. The moisture formed in the neck is sufficient to prevent the cork
from gliding along the glass.
THE FLYING COIN
You may be inclined to think that special apparatus is necessary to make
a coin fly from the bottom of a glass, but here is shown a very simple
method by which the trick may be performed at any moment in your home.
First procure a liqueur glass of conical shape, having in its largest
part a diameter not much greater than that of a silver dollar. At the
bottom of this glass place a quarter, and above it, near the top of the
glass, a silver dollar, the latter forming a kind of cover (A, Fig. 2).
Now declare to your friends that, without touching the dollar, you will
make the quarter jump from the glass.
[Illustration: FIG. 2.--The flying coin.]
This at first seems to them an impossibility, but all you have to do is
to blow very strongly on the edge of the dollar. This will make the
larger coin turn about on its own diameter into a vertical position,
whilst the compressed air under the quarter causes the latter to fly out
of the glass, after which the dollar returns to its original horizontal
position.
A CIGARETTE-SMOKING LAMP-GLASS
This is a very striking experiment, and is quite easy to perform. The
apparatus is also quite simple, and may be easily obtained. It consists
of a lamp-chimney, a cork, a cigarette, together with two little valves.
[Illustration: FIG. 3.--The self-smoking cigarette.]
Tightly cork up one end of the lamp-chimney with a large cork, thus
hermetically sealing it. In this cork bore two holes, one following the
line of the cork’s axis and having exactly the same diameter as the
cigarette: the other being oblique with respect to this axis, and having
a much smaller diameter (Fig. 3).
[Illustration: FIG. 4.--The self-smoking cigarette.]
It is now necessary to make the valves. This is done by cutting from a
glove two round pieces of the skin or leather, which, by means of pins,
may be fixed over the holes, one being above the little hole on the top
of the cork, the other over the large hole on the under side of the
cork.
The first valve allows the smoke to escape, at the same time preventing
the entrance of any external air, whilst the lower valve allows the
smoke from the cigarette to enter the glass tube, but will not allow it
to escape by the same hole.
Having thus made the valves, next plunge the tube in the water as far as
the cork, and place the cigarette in the hole made for it. After having
lit it, proceed to make the lamp-chimney smoke it.
In order that it may inhale the smoke, slowly raise the glass. By so
doing a vacuum is produced between the surface of the water and the
bottom of the cork. To destroy this vacuum, air must enter from without,
and the only means of its entrance is through the cigarette, as the
valve on the top of the cork remains tightly closed. In passing through
the cigarette this current of air greatly assists combustion, and the
smoke formed will pass with the air into the lamp-chimney.
If now the glass be lowered again, the air which is compressed by so
doing closes the central valve, whilst that above the oblique tube is
opened. From this valve the smoke will ascend in clouds (Fig. 4).
In this way the glass may be made to smoke the whole cigarette.
WATER SWINGING
Nearly every one has seen, at the circus or elsewhere, an acrobat
executing giddy circular movements with a glass of water, and doubtless
has wondered how it is that none of the liquid is spilt. This is due to
the action of centrifugal force.
Having placed the glass full of water on the table, it is only a matter
of taking it properly with the hand, holding it at arm’s length, and,
with the arm thus extended, describing a complete circle, after which it
may be placed upon the table without the loss of a single drop.
To insure the success of the experiment, particular attention must be
paid to the manner in which the glass is held. Instead of taking it as
you would when drinking, hold it with the hand reversed, the palm being
turned upwards, as shown in Fig. 5.
[Illustration: FIG. 5.--Centrifugal force experiment. First position.]
Without hesitation throw the arm in the air, and swing it, not too
quickly, but without shaking it, in the direction of the arrows in the
diagram (Fig. 6).
[Illustration: FIG. 6.--Swinging the glass.]
[Illustration: FIG. 7.--The action completed.]
After one complete revolution the glass should be as shown by Fig. 7;
whilst in this position it may be placed on the table. At first it is
advisable to practice this experiment with water, but, as more skill is
acquired, other liquids, such as milk or wine, may be used as occasion
permits.
[Illustration: FIG. 8.--The spoon mirror.]
A NOVEL MIRROR
A simple method of illuminating the back of the mouth and throat,
especially when throat trouble is suspected, may often be found
extremely useful. Here is a means of supplying, at a moment’s notice, an
extemporized illuminant of this kind.
Take a well-cleaned spoon, and hold it against a candle flame, when you
form an excellent mirror, which will permit you to concentrate the rays
of light and produce at the back of the throat enough illumination for
the making of a careful examination (Fig. 8).
A silver spoon, moreover, allows you to study the curious properties of
curved mirrors. Holding the hollow part of the spoon before your face,
notice that the head is at the bottom; turn the spoon round, and you
have the bulging part a convex mirror, which will show an image, very
long and narrow. If you approach this face in the spoon little by
little, you will see the nose attain the most amusing proportions.
A DISAPPEARING COIN
If you look at an object which has been placed in water, owing to the
phenomenon of refraction, the article appears in a different position
from that in which it really is.
It is due to this phenomenon, therefore, that a stick, when half plunged
into water, seems to be bent or broken.
A very interesting experiment based on this principle is the
following:--
Take a bowl full of water, and at the bottom place a coin. Next request
one of your friends to lower his head until his eye, the edge of the
bowl, and the near edge of the cent, appear to be in the same line.
As a matter of fact, it is not the coin itself that your friend can see,
but only the image created by refraction.
Now, keeping your friend in the same position, inform him that you
intend to make the coin disappear from his view.
To do this, remove some of the water from the bowl, which may be
accomplished by means of a small syringe (Fig. 9).
[Illustration: FIG. 9.--The disappearing coin.]
Directly you lower the level of the water, your friend will no longer be
able to see the image of the coin, which will be hidden by the side of
the bowl. If, however, the extracted water be replaced, the image of the
coin immediately reappears.
ELECTRIFIED PAPER
Very few people realize that paper can be electrified at a moment’s
notice, no special apparatus for the purpose being required.
Take a piece of light paper, which should have been well dried, and rub
it briskly with a clothes brush, silk handkerchief, or even the open
hand.
After a little time the paper, becoming electrified, will adhere to your
face, your hands, or your clothes, as easily as if it were attached by
means of gum.
Nor is this property confined to thin paper. Thick paper, when dried,
will act in the same manner. For instance, take a postcard, dry it, and
rub it, and you will notice that, as is the case with sealing-wax,
glass, sulphur, &c., the card has the power of attracting light bodies,
such as small pieces of cork.
The following interesting experiment may be carried out with an
electrified postcard and a walking-stick.
Balance the walking-stick over the back of a chair, and announce that
you can make the stick fall without touching it, without blowing it, or
without interfering with the chair. This is easily possible by utilizing
the electrified postcard.
[Illustration: FIG. 10.--The electrified postcard.]
First rub it on the sleeve of your coat. Now hold it near one end of the
stick, and you will notice that the latter follows it as iron follows a
magnet (Fig. 10), until the moment when the equilibrium being destroyed,
the stick falls to the ground.
Of course the experiment may be varied by using any other suitable
article in place of the stick, as for instance a fishing-rod.
ELECTRIFIED BALLOONS
From the last experiment it may have been gathered that if a piece of
paper is dried and rubbed with a silk handkerchief or the dry hand it
will adhere to the face, arms, or clothing.
It may not be so widely known, however, that if toy balloons be filled
with air, and then stroked for a short time with a piece of fur, they
will act in the same way as the electrified paper.
It is rather amusing to see these balloons, after being treated thus,
placed against the wall or ceiling, where they will stick as if they
were glued there.
[Illustration: FIG. 11.--The electrified balloons.]
Having entertained your friends in this manner, you may, by way of a
little change, take two of these toy balloons, and, after having
electrified them, suspend them from the same point by means of two
silken threads.
You will be surprised to find that the balloons now repel each other in
the same manner as pith balls do (Fig. 11).
EXPLODING FLOUR
Flour will create an explosion!
Take a large handful of flour, and leave it for some time near the fire,
in order that every trace of dampness may be expelled.
Whilst the flour is drying take a large tin box (a cracker tin will do
admirably), and near the bottom make a small hole.
Through this hole pass the end of a piece of india-rubber tubing, and
place the handful of dry flour in front of it.
At the other end of the box place a short piece of candle, and after
lighting it, cover the box with the lid, taking care that it is not too
firmly fixed.
If you now blow down the tube with your mouth, or better still, with a
pair of bellows an explosion at once takes place, as a result of which
the lid will be blown off (Fig. 12).
[Illustration: FIG. 12.--Exploding flour.]
If flour be not available the experiment may be performed with equal
success by using fine dust, such as may be found on the backs of
pictures, or collected from any elevated parts of the room.
THE APPARENTLY IMPOSSIBLE
Have you ever had tea on the top of a mountain? If so, you will agree
that your cup of tea could by no means be termed excellent.
Now, why is it that a cup of tea made on a mountain-top is much inferior
to one made at a lower level? If the fault lay in the tea, the defect
could be easily remedied, but such is not the case, for it depends upon
the fact that water on the top of a mountain boils at a lower
temperature than water at the sea-level.
In order to make a good cup of tea, the water must boil at a temperature
very near 100° C., and it is at this temperature that the water is
generally boiled in your homes.
Why is it, then, that water boils at different temperatures at different
altitudes? It is because, as the altitude is increased, so the
atmospheric pressure becomes less.
At sea-level, atmospheric pressure is equal to about 15 lbs. to the
square inch, but at the top of a mountain it is much less. The greater
the atmospheric pressure the more heat is required before the bubbles of
vapor formed within the water can break at the surface.
After this explanation, perhaps the subjoined experiment will be
attempted with additional interest.
Take a flask, to which should be fitted a good cork or india-rubber
stopper, and in it boil some water, taking care of course to remove the
stopper beforehand.
After some minutes the steam from the boiling water will have expelled
all the air from the flask. Now remove the source of heat, at the same
time quickly inserting the stopper.
If the flask is allowed to stand for a minute or two, the temperature of
the water will fall considerably below 100° C.
Next inform your friends that, without applying any extra heat, you will
cause the water in the flask to boil vigorously again. This seems to
them impossible, especially when you tell them that you are going to do
it by means of cold water. Quickly turn the glass upside down, and
squeeze a sponge soaked in cold water on its upturned under-surface.
Immediately the liquid inside will begin to boil, as if extra heat had
been applied (Fig. 13).
[Illustration: FIG. 13.--A curious boiling experiment.]
But how are you to explain this apparently extraordinary phenomenon?
Well, directly the cold water comes in contact with the flask it causes
the steam contained therein to condense, and, as no air can enter,
thanks to the well-fitting cork, the pressure on the surface of the warm
water is now considerably less than it was before.
Directly the pressure is lessened the vapor bubbles contained within the
warm water are able to rise to the surface, and the water is seen to
boil merrily.
MAKING COAL GAS
Here is a very simple way of obtaining coal gas.
Procure an ordinary long clay tobacco pipe, the bowl of which should be
filled with very small pieces of coal. Carefully cover the top with soft
clay, and put the bowl in the fire, with the long stem protruding
through the bars. Now watch this end of the pipe very closely and see
what happens.
[Illustration: FIG. 14.--Simple gas-making.]
Very soon you will notice a light-colored smoke issuing from the
mouthpiece, but after a time this smoke disappears. But what happens if
you hold a lighted match to the mouthpiece of the pipe? Immediately a
bright yellow flame appears (Fig. 14).
The gas now burning is the same gas as is burnt in your house, although
this latter, of course, is much purer.
If now you take the pipe from the fire, allow it to cool and then break
it, you will be surprised to find that its contents have changed in
appearance, for, in place of the coal, you will see what looks like a
cinder. This is the coke. Thus you have manufactured gas from coal, at
the same time producing coke.
EXPERIMENTS WITH CARBONIC ACID GAS
In a previous chapter, when describing how to make a miniature cannon,
it was explained that the “gunpowder” with which the “shell” was fired
is in reality carbonic acid gas.
It may not be amiss to show how to generate it, in order that you may
discover for yourselves some of its properties.
There are several ways of obtaining carbonic acid gas, but most of these
are of a complicated nature. The following, however, is an extremely
simple method.
Take a 6-oz. or 8-oz. flask, and fit it with a cork with a hole, in
which may be fitted a piece of glass tubing.
This tubing should be bent twice at right angles, as shown in Fig. 15,
and the longer end should be allowed to dip into a large glass.
[Illustration: FIG. 15.--A carbonic acid gas experiment.]
Into the flask pour a little lemonade, soda water or ginger ale, and
after replacing the cork or tube, heat the flask by means of a
gas-burner or spirit lamp.
You will notice that bubbles of gas are given off, and, as this gas is
considerably heavier than air, it will, after being forced up the tube,
displace the air in the glass, and gradually fill it. To test whether
the glass is full, hold a match in the top. If the match is
extinguished, the glass which is full may be removed. In this way
several glasses can be filled, care being taken to cover each with a
glass plate or cardboard disc to prevent diffusion.
From this experiment you will have discovered the three main properties
of this gas (commonly known as carbon dioxide)--that it is colorless, is
considerably heavier than air, and will not support combustion. Its high
density affords another interesting experiment, which consists of
pouring the gas from one glass to another (Fig. 16).
[Illustration: FIG. 16.--Pouring carbon dioxide from one glass to
another.]
Take two glasses, one full of air and the other containing the carbonic
acid gas, and into each plunge a lighted match. The match of course will
burn in the glass containing air, whilst it will be immediately
extinguished when it comes in contact with the carbon dioxide. You have
thus clearly shown which glass contains air and which contains the gas.
Now take the glass containing the gas and pour its contents into the
other glass, in exactly the same way as you would pour in water. Again
test with a lighted match and you will find that the gas has passed from
one glass to another, thus proving that it is much heavier than air.
Next take two glasses, one containing air and the other carbonic acid
gas, and, by means of a clay pipe, blow a soap bubble into each,
carefully watching the different manners in which they behave. That
dropped into the glass containing air will sink to the bottom, where,
coming in contact with the glass, it will burst. The other bubble,
however, as soon as it reaches the gas in the glass, rebounds owing to
the high density of the carbon dioxide, but after a time, when it has
settled down, it will float motionless on the surface (Fig. 17).
[Illustration: FIG. 17.--Soap bubbles in A (air), and B, carbon
dioxide.]
Before you finish experimenting you should know how to detect the
presence of carbon dioxide. Take a little lime water, which may be
obtained from any druggist, and pour it into a glass containing carbon
dioxide. Shake the glass, and carefully observe the change which takes
place. The lime water, which was previously colorless, has assumed a
certain milkiness, and if allowed to stand the white powder causing this
milkiness will settle at the bottom of the glass. This powder proves to
be calcium carbonate, or chalk, which is always formed when lime water
comes in contact with carbon dioxide, so that you have here a means of
detecting the presence of carbon dioxide. Breathe into a little lime
water and you will learn, from the milky appearance it at once assumes,
that the air we exhale contains a certain quantity of this interesting
gas.