Bertha M. Clark - General Science

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GENERAL SCIENCE

BY

BERTHA M. CLARK, PH.D.

HEAD OF THE SCIENCE DEPARTMENT

WILLIAM PENN HIGH SCHOOL FOR GIRLS, PHILADELPHIA

NEW YORK - CINCINNATI - CHICAGO

AMERICAN BOOK COMPANY

1912

PREFACE

This book is not intended to prepare for college entrance
examinations; it will not, in fact, prepare for any of the present-day
stock examinations in physics, chemistry, or hygiene, but it should
prepare the thoughtful reader to meet wisely and actively some of
life's important problems, and should enable him to pass muster on the
principles and theories underlying scientific, and therefore economic,
management, whether in the shop or in the home.

We hear a great deal about the conservation of our natural resources,
such as forests and waterways; it is hoped that this book will show
the vital importance of the conservation of human strength and health,
and the irreparable loss to society of energy uselessly dissipated,
either in idle worry or in aimless activity. Most of us would reproach
ourselves for lack of shrewdness if we spent for any article more than
it was worth, yet few of us consider that we daily expend on domestic
and business tasks an amount of energy far in excess of that actually
required. The farmer who flails his grain instead of threshing it
wastes time and energy; the housewife who washes with her hands alone
and does not aid herself by the use of washing machine and proper
bleaching agents dissipates energy sadly needed for other duties.

The Chapter on machines is intended not only as a stimulus to the
invention of further labor-saving devices, but also as an eye opener
to those who, in the future struggle for existence, must perforce go
to the wall unless they understand how to make use of contrivances
whereby man's limited physical strength is made effective for larger
tasks.

The Chapter on musical instruments is more detailed than seems
warranted at first sight; but interest in orchestral instruments is
real and general, and there is a persistent desire for intelligent
information relative to musical instruments. The child of the laborer
as well as the child of the merchant finds it possible to attend some
of the weekly orchestral concerts, with their tiers of cheap seats,
and nothing adds more to the enjoyment and instruction of such hours
than an intimate acquaintance with the leading instruments. Unless
this is given in the public schools, a large percentage of mankind is
deprived of it, and it is for this reason that so large a share of the
treatment of sound has been devoted to musical instruments.

The treatment of electricity is more theoretical than that used in
preceding Chapters, but the subject does not lend itself readily to
popular presentation; and, moreover, it is assumed that the
information and training acquired in the previous work will give the
pupil power to understand the more advanced thought and method.

The real value of a book depends not so much upon the information
given as upon the permanent interest stimulated and the initiative
aroused. The youthful mind, and indeed the average adult mind as
well, is singularly non-logical and incapable of continued
concentration, and loses interest under too consecutive thought and
sustained style. For this reason the author has sacrificed at times
detail to general effect, logical development to present-day interest
and facts, and has made use of a popular, light style of writing as
well as of the more formal and logical style common to books of
science.

No claim is made to originality in subject matter. The actual facts,
theories, and principles used are such as have been presented in
previous textbooks of science, but the manner and sequence of
presentation are new and, so far as I know, untried elsewhere. These
are such as in my experience have aroused the greatest interest and
initiative, and such as have at the same time given the maximum
benefit from the informational standpoint. In no case, however, is
mental training sacrificed to information; but mental development is
sought through the student's willing and interested participation in
the actual daily happenings of the home and the shop and the field,
rather than through formal recitations and laboratory experiments.

Practical laboratory work in connection with the study of this book is
provided for in my _Laboratory Manual in General Science_, which
contains directions for a series of experiments designed to make the
pupil familiar with the facts and theories discussed in the textbook.

I have sought and have gained help from many of the standard
textbooks, new and old. The following firms have kindly placed cuts
at my disposal, and have thus materially aided in the preparation of
the illustrations: American Radiator Company; Commercial Museum,
Philadelphia; General Electric Company; Hershey Chocolate Company;
_Scientific American_; The Goulds Manufacturing Company; Victor
Talking Machine Company. Acknowledgment is also due to Professor Alvin
Davison for figures 19, 23, 29, 142, and 161.

Mr. W.D. Lewis, Principal of the William Penn High School, has read
the manuscript and has given me the benefit of his experience and
interest. Miss. Helen Hill, librarian of the same school, has been of
invaluable service as regards suggestions and proof reading. Miss.
Droege, of the Baldwin School, Bryn Mawr, has also been of very great
service. Practically all of my assistants have given of their time and
skill to the preparation of the work, but the list is too long for
individual mention.

BERTHA M. CLARK.

WILLIAM PENN HIGH SCHOOL.

CONTENTS

CHAPTER

I. HEAT

II. TEMPERATURE AND HEAT

III. OTHER FACTS ABOUT HEAT

IV. BURNING OR OXIDATION

V. FOOD

VI. WATER

VII. AIR

VIII. GENERAL PROPERTIES OF GASES

IX. INVISIBLE OBJECTS

X. LIGHT

XI. REFRACTION

XII. PHOTOGRAPHY

XIII. COLOR

XIV. HEAT AND LIGHT AS COMPANIONS

XV. ARTIFICIAL LIGHTING

XVI. MAN'S WAY OF HELPING HIMSELF

XVII. THE POWER BEHIND THE ENGINE

XVIII. PUMPS AND THEIR VALUE TO MAN

XIX. THE WATER PROBLEM OF A LARGE CITY

XX. MAN'S CONQUEST OF SUBSTANCES

XXI. FERMENTATION

XXII. BLEACHING

XXIII. DYEING

XXIV. CHEMICALS AS DISINFECTANTS AND PRESERVATIVES

XXV. DRUGS AND PATENT MEDICINES

XXVI. NITROGEN AND ITS RELATION TO PLANTS

XXVII. SOUND

XXVIII. MUSICAL INSTRUMENTS

XXIX. SPEAKING AND HEARING

XXX. ELECTRICITY

XXXI. SOME USES OF ELECTRICITY

XXXII. MODERN ELECTRICAL INVENTIONS

XXXIII. MAGNETS AND CURRENTS

XXXIV. HOW ELECTRICITY MAY BE MEASURED

XXXV. HOW ELECTRICITY IS OBTAINED ON A LARGE SCALE

INDEX

GENERAL SCIENCE

CHAPTER I

HEAT

I. Value of Fire. Every day, uncontrolled fire wipes out human
lives and destroys vast amounts of property; every day, fire,
controlled and regulated in stove and furnace, cooks our food and
warms our houses. Fire melts ore and allows of the forging of iron, as
in the blacksmith's shop, and of the fashioning of innumerable objects
serviceable to man. Heated boilers change water into the steam which
drives our engines on land and sea. Heat causes rain and wind, fog and
cloud; heat enables vegetation to grow and thus indirectly provides
our food. Whether heat comes directly from the sun or from artificial
sources such as coal, wood, oil, or electricity, it is vitally
connected with our daily life, and for this reason the facts and
theories relative to it are among the most important that can be
studied. Heat, if properly regulated and controlled, would never be
injurious to man; hence in the following paragraphs heat will be
considered merely in its helpful capacity.

2. General Effect of Heat. _Expansion and Contraction_. One of the
best-known effects of heat is the change which it causes in the size
of a substance. Every housewife knows that if a kettle is filled with
cold water to begin with, there will be an overflow as soon as the
water becomes heated. Heat causes not only water, but all other
liquids, to occupy more space, or to expand, and in some cases the
expansion, or increase in size, is surprisingly large. For example, if
100 pints of ice water is heated in a kettle, the 100 pints will
steadily expand until, at the boiling point, it will occupy as much
space as 104 pints of ice water.

The expansion of water can be easily shown by heating a flask (Fig. I)
filled with water and closed by a cork through which a narrow tube
passes. As the water is heated, it expands and forces its way up the
narrow tube. If the heat is removed, the liquid cools, contracts, and
slowly falls in the tube, resuming in time its original size or
volume. A similar observation can be made with alcohol, mercury, or
any other convenient liquid.

[Illustration: FIG. 1.--As the water becomes warmer it expands and
rise in the narrow tube.]

Not only liquids are affected by heat and cold, but solids also are
subject to similar changes. A metal ball which when cool will just
slip through a ring (Fig. 2) will, when heated, be too large to slip
through the ring. Telegraph and telephone wires which in winter are
stretched taut from pole to pole, sag in hot weather and are much too
long. In summer they are exposed to the fierce rays of the sun, become
strongly heated, and expand sufficiently to sag. If the wires were
stretched taut in the summer, there would not be sufficient leeway for
the contraction which accompanies cold weather, and in winter they
would snap.

[Illustration: FIG. 2--When the ball is heated, it become too large to
slip through the ring.]

Air expands greatly when heated (Fig. 3), but since air is practically
invisible, we are not ordinarily conscious of any change in it. The
expansion of air can be readily shown by putting a drop of ink in a
thin glass tube, inserting the tube in the cork of a flask, and
applying heat to the flask (Fig. 4). The ink is forced up the tube by
the expanding air. Even the warmth of the hand is generally sufficient
to cause the drop to rise steadily in the tube. The rise of the drop
of ink shows that the air in the flask occupies more space than
formerly, and since the quantity of air has not changed, each cubic
inch of space must hold less warm air than| it held of cold air; that
is, one cubic inch of warm air weighs less than one cubic inch of cold
air, or warm air is less dense than cold air. All gases, if not
confined, expand when heated and contract as they cool. Heat, in
general, causes substances to expand or become less dense.

[Illustration: FIG. 3--As the air in _A_ is heated, it expands and
escapes in the form of bubbles.]

3. Amount of Expansion and Contraction. While most substances expand
when heated and contract when cooled, they are not all affected
equally by the same changes in temperature. Alcohol expands more than
water, and water more than mercury. Steel wire which measures 1/4 mile
on a snowy day will gain 25 inches in length on a warm summer day, and
an aluminum wire under the same conditions would gain 50 inches in
length.

[Illustration: FIG. 4.--As the air in _A_ is heated, it expands and
forces the drop of ink up the tube.]

4. Advantages and Disadvantages of Expansion and Contraction. We owe
the snug fit of metal tires and bands to the expansion and contraction
resulting from heating and cooling. The tire of a wagon wheel is made
slightly smaller than the wheel which it is to protect; it is then
put into a very hot fire and heated until it has expanded sufficiently
to slip on the wheel. As the tire cools it contracts and fits the
wheel closely.

In a railroad, spaces are usually left between consecutive rails in
order to allow for expansion during the summer.

The unsightly cracks and humps in cement floors are sometimes due to
the expansion resulting from heat (Fig. 5). Cracking from this cause
can frequently be avoided by cutting the soft cement into squares, the
spaces between them giving opportunity for expansion just as do the
spaces between the rails of railroads.

[Illustration: FIG. 5: A cement walk broken by expansion due to sun
heat.]

In the construction of long wire fences provision must be made for
tightening the wire in summer, otherwise great sagging would occur.

Heat plays an important part in the splitting of rocks and in the
formation of debris. Rocks in exposed places are greatly affected by
changes in temperature, and in regions where the changes in
temperature are sudden, severe, and frequent, the rocks are not able
to withstand the strain of expansion and contraction, and as a result
crack and split. In the Sahara Desert much crumbling of the rock into
sand has been caused by the intense heat of the day followed by the
sharp frost of night. The heat of the day causes the rocks to expand,
and the cold of night causes them to contract, and these two forces
constantly at work loosen the grains of the rock and force them out of
place, thus producing crumbling.

[Illustration: FIG. 6.--Splitting and crumbling of rock caused by
alternating heat and cold.]

The surface of the rock is the most exposed part, and during the day
the surface, heated by the sun's rays, expands and becomes too large
for the interior, and crumbling and splitting result from the strain.
With the sudden fall of temperature in the late afternoon and night,
the surface of the rock becomes greatly chilled and colder than the
rock beneath; the surface rock therefore contracts and shrinks more
than the underlying rock, and again crumbling results (Fig. 6).

[Illustration: FIG. 7.--Debris formed from crumbled rock.]

On bare mountains, the heating and cooling effects of the sun are very
striking(Fig. 7); the surface of many a mountain peak is covered with
cracked rock so insecure that a touch or step will dislodge the
fragments and start them down the mountain slope. The lower levels of
mountains are frequently buried several feet under debris which has
been formed in this way from higher peaks, and which has slowly
accumulated at the lower levels.

5. Temperature. When an object feels hot to the touch, we say that
it has a high temperature; when it feels cold to the touch, that it
has a low temperature; but we are not accurate judges of heat. Ice
water seems comparatively warm after eating ice cream, and yet we know
that ice water is by no means warm. A room may seem warm to a person
who has been walking in the cold air, while it may feel decidedly cold
to some one who has come from a warmer room. If the hand is cold,
lukewarm water feels hot, but if the hand has been in very hot water
and is then transferred to lukewarm water, the latter will seem cold.
We see that the sensation or feeling of warmth is not an accurate
guide to the temperature of a substance; and yet until 1592, one
hundred years after the discovery of America, people relied solely
upon their sensations for the measurement of temperature. Very hot
substances cannot be touched without injury, and hence inconvenience
as well as the necessity for accuracy led to the invention of the
thermometer, an instrument whose operation depends upon the fact that
most substances expand when heated and contract when cooled.

[Illustration: FIG. 8.--Making a thermometer.]

6. The Thermometer. The modern thermometer consists of a glass tube
at the lower end of which is a bulb filled with mercury or colored
alcohol (Fig. 8). After the bulb has been filled with the mercury, it
is placed in a beaker of water and the water is heated by a Bunsen
burner. As the water becomes warmer and warmer the level of the
mercury in the tube steadily rises until the water boils, when the
level remains stationary (Fig. 9). A scratch is made on the tube to
indicate the point to which the mercury rises when the bulb is placed
in boiling water, and this point is marked 212 deg.. The tube is then
removed from the boiling water, and after cooling for a few minutes,
it is placed in a vessel containing finely chopped ice (Fig. 10). The
mercury column falls rapidly, but finally remains stationary, and at
this level another scratch is made on the tube and the point is marked
32 deg.. The space between these two points, which represent the
temperatures of boiling water and of melting ice, is divided into 180
equal parts called degrees. The thermometer in use in the United
States is marked in this way and is called the Fahrenheit thermometer
after its designer. Before the degrees are etched on the thermometer
the open end of the tube is sealed.

[Illustration: FIG. 9.--Determining one of the fixed points of a
thermometer.]

The Centigrade thermometer, in use in foreign countries and in all
scientific work, is similar to the Fahrenheit except that the fixed
points are marked 100 deg. and 0 deg., and the interval between the points is
divided into 100 equal parts instead of into 180.

_The boiling point of water is 212 deg. F. or 100 deg. C_.

_The melting point of ice is 32 deg. F. or 0 deg. C_.

Glass thermometers of the above type are the ones most generally used,
but there are many different types for special purposes.

[Illustration: FIG. 10.--Determining the lower fixed point of a
thermometer.]

7. Some Uses of a Thermometer. One of the chief values of a
thermometer is the service it has rendered to medicine. If a
thermometer is held for a few minutes under the tongue of a normal,
healthy person, the mercury will rise to about 98.4 deg. F. If the
temperature of the body registers several degrees above or below this
point, a physician should be consulted immediately. The temperature of
the body is a trustworthy indicator of general physical condition;
hence in all hospitals the temperature of patients is carefully taken
at stated intervals.

Commercially, temperature readings are extremely important. In sugar
refineries the temperature of the heated liquids is observed most
carefully, since a difference in temperature, however slight, affects
not only the general appearance of sugars and sirups, but the quality
as well. The many varieties of steel likewise show the influence which
heat may have on the nature of a substance. By observation and tedious
experimentation it has been found that if hardened steel is heated to
about 450 deg. F. and quickly cooled, it gives the fine cutting edge of
razors; if it is heated to about 500 deg. F. and then cooled, the metal is
much coarser and is suitable for shears and farm implements; while if
it is heated but 50 deg. F. higher, that is, to 550 deg. F., it gives the fine
elastic steel of watch springs.

[Illustration: FIG. 11.--A well-made commercial thermometer.]

A thermometer could be put to good use in every kitchen; the
inexperienced housekeeper who cannot judge of the "heat" of the oven
would be saved bad bread, etc., if the thermometer were a part of her
equipment. The thermometer can also be used in detecting adulterants.
Butter should melt at 94 deg. F.; if it does not, you may be sure that it
is adulterated with suet or other cheap fat. Olive oil should be a
clear liquid above 75 deg. F.; if, above this temperature, it looks
cloudy, you may be sure that it too is adulterated with fat.

8. Methods of Heating Buildings. _Open Fireplaces and Stoves._
Before the time of stoves and furnaces, man heated his modest dwelling
by open fires alone. The burning logs gave warmth to the cabin and
served as a primitive cooking agent; and the smoke which usually
accompanies burning bodies was carried away by means of the chimney.
But in an open fireplace much heat escapes with the smoke and is lost,
and only a small portion streams into the room and gives warmth.

When fuel is placed in an open fireplace (Fig. 12) and lighted, the
air immediately surrounding the fire becomes warmer and, because of
expansion, becomes lighter than the cold air above. The cold air,
being heavier, falls and forces the warmer air upward, and along with
the warm air goes the disagreeable smoke. The fall of the colder and
heavier air, and the rise of the warmer and hence lighter air, is
similar to the exchange which takes place when water is poured on oil;
the water, being heavier than oil, sinks to the bottom and forces the
oil to the surface. The warmer air which escapes up the chimney
carries with it the disagreeable smoke, and when all the smoke is got
rid of in this way, the chimney is said to draw well.

[Illustration: FIG. 12.--The open fireplace as an early method of
heating.]

As the air is heated by the fire it expands, and is pushed up the
chimney by the cold air which is constantly entering through loose
windows and doors. Open fireplaces are very healthful because the air
which is driven out is impure, while the air which rushes in is fresh
and brings oxygen to the human being.

But open fireplaces, while pleasant to look at, are not efficient for
either heating or cooking. The possibilities for the latter are
especially limited, and the invention of stoves was a great advance in
efficiency, economy, and comfort. A stove is a receptacle for fire,
provided with a definite inlet for air and a definite outlet for
smoke, and able to radiate into the room most of the heat produced
from the fire which burns within. The inlet, or draft, admits enough
air to cause the fire to burn brightly or slowly as the case may be.
If we wish a hot fire, the draft is opened wide and enough air enters
to produce a strong glow. If we wish a low fire, the inlet is only
partially opened, and just enough air enters to keep the fuel
smoldering.

When the fire is started, the damper should be opened wide in order to
allow the escape of smoke; but after the fire is well started there is
less smoke, and the damper may be partly closed. If the damper is kept
open, coal is rapidly consumed, and the additional heat passes out
through the chimney, and is lost to use.

9. Furnaces. _Hot Air_. The labor involved in the care of numerous
stoves is considerable, and hence the advent of a central heating
stove, or furnace, was a great saving in strength and fuel. A furnace
is a stove arranged as in Figure 13. The stove _S_, like all other
stoves, has an inlet for air and an outlet _C_ for smoke; but in
addition, it has built around it a chamber in which air circulates and
is warmed. The air warmed by the stove is forced upward by cold air
which enters from outside. For example, cold air constantly entering
at _E_ drives the air heated by _S_ through pipes and ducts to the
rooms to be heated.

The metal pipes which convey the heated air from the furnace to the
ducts are sometimes covered with felt, asbestos, or other
non-conducting material in order that heat may not be lost during
transmission. The ducts which receive the heated air from the pipes
are built in the non-conducting walls of the house, and hence lose
practically no heat. The air which reaches halls and rooms is
therefore warm, in spite of its long journey from the cellar.

[Illustration: FIG. 13.--A furnace. Pipes conduct hot air to the
rooms.]

Not only houses are warmed by a central heating stove, but whole
communities sometimes depend upon a central heating plant. In the
latter case, pipes closely wrapped with a non-conducting material
carry steam long distances underground to heat remote buildings.
Overbrook and Radnor, Pa., are towns in which such a system is used.

10. Hot-water Heating. The heated air which rises from furnaces is
seldom hot enough to warm large buildings well; hence furnace heating
is being largely supplanted by hot-water heating.

The principle of hot-water heating is shown by the following simple
experiment. Two flasks and two tubes are arranged as in Figure 15, the
upper flask containing a colored liquid and the lower flask clear
water. If heat is applied to _B_, one can see at the end of a few
seconds the downward circulation of the colored liquid and the upward
circulation of the clear water. If we represent a boiler by _B_, a
radiator by the coiled tube, and a safety tank by _C_, we shall have a
very fair illustration of the principle of a hot-water heating system.
The hot water in the radiators cools and, in cooling, gives up its
heat to the rooms and thus warms them.

[Illustration: FIG. 14.--Hot-water heating.]

In hot-water heating systems, fresh air is not brought to the rooms,
for the radiators are closed pipes containing hot water. It is largely
for this reason that thoughtful people are careful to raise windows at
intervals. Some systems of hot-water heating secure ventilation by
confining the radiators to the basement, to which cold air from
outside is constantly admitted in such a way that it circulates over
the radiators and becomes strongly heated. This warm fresh air then
passes through ordinary flues to the rooms above.

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