Science for beginners

Preface

This book is in effect a simplification, for younger pupils, of the authors' "First Course in General Science." There are fewer quantitative conceptions, many mathematical problems have been eliminated, and, where it has been possible without sacrificing clearness, much detail has been omitted. The chapters on Weather and Microorganisms have been made far less technical. The logical and seasonal order of topics has been improved by following the discussion of Foods with the chapter on Refrigeration and preceding it with the treatment of Microorganisms. In fact, the whole treatment has been so largely rewritten that it may fairly be regarded as a new book. It discusses, in terms that the youthful mind can understand, phenomena of science constantly met in the home, the school, and the community. It arouses the pupil's curiosity about them and sets him to finding the explanation of them. Each topic is pursued far enough to avoid superficiality and to give continuity to the course. The course is progressive; the earlier chapters are relatively easy; as the ability of the pupil grows, the course becomes correspondingly difficult. Numerous cross references are given to stimulate frequent reviews. Topics not essentially important in the environment of any class, or in the environment of the community, msCy easily be omitted without seriously breaking the continuity of the course.

Like its predecessor this book assumes that the first year of science instruction should not aim primarily to survey the entire field of nature and present scattered bits and choice morsels from every special science in order that the pupil may decide in which of the sciences he would like to special-

iii iv PREFACE

ize further. Nor is first-year science regarded as only an introduction to the special sciences. It has been shown to have a vastly more important function to perform, namely to give a rational, orderly, scientific understanding of the pupil's environment to the end that he may correctly interpret it. General science has justified itself by its own intrinsic value as a training for life's work.

We wish to express our appreciation of the aid rendered by those who have assisted in the preparation of the illustrations or who have granted us permission to use illustrations from their publications. The hearty cooperation of manufacturers and business men and the interest they have manifested in our efforts to present faithfully the application of science to the actual affairs of life have been most helpful. The authors wish to make particular acknowledgment of assistance from the following sources : The Century Company, Figs. 1, 59, 78, 303, 306, 311. Detroit Heating & Lighting Company, Figs. 15, 16. Westinghouse, Church, Kerr & Co., Figs. 35, 36. American Home Magazine Co., Figs. 37, 38, 39. General Electric Co., Figs. 40, 41. Central Electric Co., Figs. 31, 32, 44, 46, 47, 48. Welsbach Company, Figs. 50, 51, 52, 53. Curtis Publishing Co., Fig. 60. Kalamazoo Stove Co., Figs. 67, 99. Patric Furnace Co., Figs. 68, 69. Williamson Heating and Ventilating Co., Figs. 70, 71, 72, 83, 84, 85. American Radiator Co., Figs. 184, 185. Durham Manufacturing Co., Fig. 100. Mechanical Refrigerator Co., Fig. 224. Monthly Weather Review, Figs. 113, 115, 117, 132, 141, 153, 156, 157. Dr. S. Adolphus Knopf and Moffat, Yard & Co., Fig. 181. Hoover Suction Sweeper Co., Fig. 187. Municipal Journal, Fig. 188. Standard Sanitary Manufacturing Co., Figs. 239, 246, 260, 261. R, D. Wood & Co., Figs. 245, 249. Bishop & Babcock Company, Fig. 249. Rensselaer Manufacturing Co., Fig. 251. National Meter Co., Figs. 254, 255. International Harvester Co., Figs. 275, 314, 316, 318, 320. Singer Sewing Machine Co., Figs. 276, 277,

PREFACE V

278, 279, 280, 281, 282. Mississippi Power Co., Figs. 296, 297, 302. DeLaval Manufacturing Co., Figs. 283, 284, 285. American Book Co., Fig. 304. James Leffel & Co., Figs. 309, 310. Westinghouse Manufacturing Co., Fig. 54. Swift & Co., Figs. 212, 213, 214. Creamery Package Co., Fig. 211. United States Weather Bureau, Figs. 118, 119, 123, 124, 125, 134, 140, 142, 143, 144, 145, 154. Hersey Manufacturing Co., Fig. 253. Pearse, Greeley, and Hansen, Figs. 271, 272, 274. Erie Railroad Company, Fig. 291. John Wiley & Sons, Fig. 273. Some of the illustrations appear unmodified ; some have been adapted to their present use; others have been prepared especially for the book.

The Authors Normal, Illinois, September, 1921.

Contents

CHAPTER PAGE

I The Production and Use of Light 1

1. Primitive Lighting — 2. The Kerosene Lamp — 3. Evaporation, Boiling Temperature, and Distillation — 4. Petroleum and Its Products — 5. Properties of Gasoline — Sources of Danger: Density; Flashing Point and Burning Point — 6. The Gasoline Gas Machine — 7. Manufactured Gasoline, •and Motor Spirit — 8. Our Supply of Petroleum — 9. Illuminating Gas Lighting: Gas Meter; Reading a Meter; Pressure of Gas — 10. Electric Lighting: Incandescent and Nitrogen Lamps; Electric Wiring — 11. Natural and Artificial Lighting: Importance of Studying the Lighting Question; Direct and Diffused Light; Relative Cost of Operating Gas and Electric Lights.

Chapter I

I. PRIMITIVE LIGHTING

i. The Discovery of Fire. — There probably was a time when primitive man was without fire. In those days he had no artificial heat or light, and he ate his food uncooked. Perhaps man first obtained fire from dead trees ignited by lightning, perhaps from oil wells which are known to have been burning for centuries. With fire came warmth, light, and cooked food.

The light from the camp fire also furnished protection from wild animals. Gradually the fire came to be the center of the home. It is probable that we owe more than we realize to fire for what it has done toward building up and strengthening home ties.

2. The Primitive Lamp. — Perhaps a pine knot snatched from the fire constituted the first portable light. How recently pine knots have been in common use is shown by the

Fig. 1. — A Roman lamp.

From Stories of Useful Inventions. ( By courtesy of The Century Company.)

fact that Abraham Lincoln learned to read by the light of them. Perhaps by collecting the grease obtained from cooking and placing it in a rude vessel with a bit of bark or a thread of twisted moss for a wick, man made the first lamp. We would consider the light produced by such a lamp a poor one indeed, but the Eskimos still use such primitive lamps. The bowl is hollowed out from soapstone ; the fat comes from the animals they slay. The Eskimo lamp serves also as a stove. By its heat all their cooking is done and their snow huts are warmed.

3. Greek and Roman Lamps. — The lamps of Greece and Rome were no better than the Eskimo lamps of today, but the lamp bowls were often very costly and elaborately ornamented (Fig. 1). The rich used lamps of bronze or silver; the middle classes, lamps made of terra-cotta ; the poor, cheap iron lamps.

4. The Early Candle. — The earliest lamps could not conveniently be moved about. The oil or fat, especially when warm, spilled out of the bowl. It was noticed, probably, that when some fats were cold they became quite stiff and solid. Tallow is much more solid than lard. Someone concluded, therefore, that it would not be necessary to use a lamp bowl at all if tallow were used and a small wick imbedded in it. The tallow prepares its own bowl during the process of burning. Like lamps, candles have been used from prehistoric times.

5. Modern Candles. — While the candles our grandfathers and grandmothers made were of tallow, the modern candle is made of paraffin which is obtained from petroleum. Over 300,000,000 paraffin candles are sold in the United States each year, about two dozen candles for each family.

Exercise 1. — How the Candle Burns

Place a piece of candle upright on a square of pasteboard after melting a little of the paraffin at the bottom of the candle to make it stick. Light the candle. After it has burned three or four minutes notice what is happening to the paraffin near the wick. This

PRIMITIVE LIGHTING 3

cup corresponds to the bowl of the primitive lamp. To have a perfect cup three things are necessary : (1) There must be no draft in the room; (2) the wick must not be too large for the candle; (3) the wick must be in the center of the candle. Is it desirable to have the cup perfect? Why?

Hold one of the strands of candle wicking in a vertical position and light its upper end. Does it burn readily? Does it continue to burn? Is its flame like that of the candle flame? Is it the burning of the candle wick that is the chief cause of the candle flame? If not, what is it?

Blow out the candle flame and examine the wick. Is it wet? With what is it wet ? Does it remain wet all the time that the candle is burning? Re-light the candle and, using two iron nails, squeeze the wick; then examine the nails to see whether or not there is any paraffin on them. The wick is constantly soaked in melted paraffin while the candle burns. But is it the liquid paraffin which burns?

Re-light the candle and blow out the flame again. Notice the smoke which rises from the wick. How long does it continue to rise? Re-light the candle. Hold the lighted match in one hand. Blow out the caudle and quickly thrust the lighted match into the ?olumn of rising smoke about 1 in. above the candle. What happens? (Fig. 2.) Try the same again. Fig. 2.—

Make several trials to see how far above the tip of Lighting the the wick you can hold the match and still have the an eva P 01 - candle re-light. Does it make any difference how long you wait after blowing out the flame before applying the match? Do drafts through the room make a difference? What do you now think it is that burns?

Have you ever seen a frying pan in which bacon or eggs were frying become so hot that the smoke rising from the fat caught on fire? This sometimes happens. The fat, however, begins to smoke some time before it gets hot enough to catch on fire.

The Explanation. — All kinds of greases, fats, and oils when heated sufficiently hot give off vapors in large quantities. This simply means that these fats and oils are changed o\J heat from liquids into vapors, or gases, exactly as water is changed by heat from its form as liquid water into steam , or water vapor. It is paraffin vapor which burns in the candle flame.

Exercise 2. — The Flashing Point and the Burning Point

Put a little paraffin in a large spoon and slowly heat it until it begins to smoke, vaporize (Fig. 3). Then test the smoke, vapor, frequently with a burning match to see when it will ignite. At a certain temperature of the liquid paraffin in the spoon the vapor becomes dense enough to produce a momentary flash over the surface. The paraffin is then at the flashing point. Continue to heat the paraffin in the spoon slowly, testing the vapor as before. riG.3— Flash- When the vapor becomes dense enough to burn naraffin continuously, the paraffin has reached the burning

point.

Definitions. — The flashing point of paraffin, lard, tallow, or oil is that temperature at which the vapor arising and mixing with air produces a momentary flash when ignited.

The burning point is that temperature of the substayxce at which the vapor arising and mixing with air produces a continuous flame when once ignited.

It is now evident that in lighting a candle the burning match must be held against the wick long enough to melt and then to vaporize the paraffin in it in such quantities that the vapor is ignited by the match and burns with a continuous flame. The heat from the candle flame continues to melt and to vaporize the paraffin fast enough to produce eluding fresh a steady flame. air from the

6. Fresh Air is Necessary. — We have seen that the vapor from the heated tallow or paraffin rises and mixes with the air. Is the air really necessary that the vapor may burn? We can answer the question best by trying an experiment.

THE KEROSENE LAMP 5

Exercise 3. — Shutting the Fresh Air Away from the Candle

Light a piece of candle 1 or 2 in. in length and stand it on the table before you. Watch it for a minute to see that it burns properly. Now invert a tumbler and place it over the candle. Does the candle continue to burn? Remove the tumbler. Re-light the candle. Try the experiment again, using a 2-qt. fruit jar instead of the tumbler. Does the candle continue to burn longer this time? "Why? Re-light the candle. Again place the fruit jar over the burning candle. Watch carefully to see what happens just as the flame goes out. Is there much smoke given off for a moment after the flame dies out? What is this smoke? If it is paraffin vapor, why does it not burn? (Fig. 4.)

Now carefully raise the jar and set it aside while you re-light the candle, letting just as little fresh air into it as possible. Again place the jar over the candle and notice carefully how long the flame continues this time. Raise the jar, blow all the smoke out of it; re-light the candle and again place the jar over the candle. Does the flame burn longer than it did before? Explain.

Explanation. — As long as the wick is hot there will be plenty of paraffin vapor. But this vapor cannot burn alone. The flame is the result of the uniting of the vapor with one of the gases, oxygen, in the fresh air. The air is not fresh when the vapor has burned out the oxygen. No matter how much of the burned air and vapor you may have in the tumbler, or how well mixed they may be, you can not get a flame till you have some of the fresh, unburnt air mixed with the vapor.

II. THE KEROSENE LAMP

7. The First Kerosene Lamp. — The kerosene lamp has been in use only about 60 years. The lamps which had previously been used usually burned heavy oils and fats, which gave only low, flickering, smoky flames. During the first half of the last century whale oil was in common use along the seacoast. Whale oil lamps were less smoky and disagreeable than most lamps of the period. A few lamps had been made which burned so-called burning fluids. But these fluids were very inflammable and dangerous. Up to about 1860 candles were by far the safest and best sources of artificial light which the world had ever used.

It was in August, 1858, that the first successful oil well was sunk in Pennsylvania. Petroleum had been known for a long time, but it had never before been found in commercial quantities and little use had been made of it except as medicine. Soon after it was obtained in large quantities, the discovery was made that an oil could be obtained from crude petroleum which would burn freely and still be safe to handle. This new oil was called kerosene, though some people, supposing that it came from coal, called it coal oil. We still sometimes hear it called by that name. Inventors soon made lamps well suited for the burning of this oil. The common kerosene lamp of today is, in principle, exactly like those earliest lamps.

8. Parts of the Kerosene Lamp. — The ordinary kerosene lamp really consists of three parts: (1) The bowl for containing the oils ; (2) the wick ; (3) the burner and chimney- The wick is usually made of soft, loosely woven cotton cloth. What is its purpose ? What does it do?

Burners vary much in construction, but all have certain necessary parts, namely: (1) The cap, or crown ; (2) the

PERFORATED BASE; (3) the TUBE FOR THE WICK.

Fig. 5. — Parts of the burner.

THE KEROSEXE LAMP 7

Exercise 4. — The Use of the Burner and Chimney

Examine a burner carefully and discover these parts. Make a sketch in your notebook of your burner showing clearly each of these parts. Label all parts of your sketch somewhat as the sketch, Fig. 5, is labeled. Do not copy the sketch from the book but sketch your lamp.

Study carefully the device for regulating the height of the wick.

Light the lamp, place the chimney in position, and observe the steadiness of the flame. If there is not much draft through the room there should be very little flickering of the flame. It should burn with a steady flame.

"Wave your book past the bowl of the lamp so as to produce a strong gust of air against the under side of the burner. "What is the effect upon the flame? Can you tell why it becomes smoky? Did you increase or decrease the amount of air which was passing through the chimney and past the flame? Hold the lamp up before you and blow strongly into the bottom of the burner. What is the effect upon the flame? Is it a case of too much air or not enough?

Wrap a towel about the base of the burner to prevent air from entering through the perforated base. What is the effect upon the flame? If you could see only the upper portions of the chimney could you be certain from the behavior of the flame whether too much or too Fig. C.

little air was entering the burner? Burning

Place a piece of cardboard or window glass for an Kerosene instant on •the top of the chimney so as to close it. What burner, is the result ? What is the effect upon the flame of having too little air? What is the effect of having too much air? What do you think is the chief purpose of the burner and chimney?

Kerosene burns just as freely without the use of a burner or chimney. This can be easily shown by placing some kerosene in a tumbler and covering the tumbler with a sheet of tin in which a slit has been cut by means of a cold chisel. An ordinary lamp wick is drawn into the slit as shown in Fig. 6. In this case, however, the flame will be smoky and unsteady no matter how still the air in the room may be.

Evidently, the chief purpose of the burner and chimney is to regulate the air supply. If the air supply he either too abundant or too scarce the flame will be unsteady and smoky. We shall see later why this is so. We shall also study later the principle by which the burner and chimney regulate the air supply.

9. How Kerosene Burns. — Just as we proved that it was not the liquid paraffin which burned in the case of the candle, so we can show that it is not the liquid kerosene which burns in the case of the kerosene lamp.

Exercise 5. — It is Kerosene Vapor that Burns

Remove the chimney from the lamp. Light it. Hold the lighted match ready to apply. Blow out the flame. Quickly apply the lighted match to the rising column of smoke. Does it ignite? If not, be quicker in applying the match next time. Repeat the experiment to see how far above the wick you are able to ignite the vapor.

Have you ever noticed a strong odor of kerosene in the room after "blowing out" a lamp? (Art. 86.) Explain.

Can this be prevented by first turning the wick down so as to produce a low flame before blowing it out? Explain.

10. Center Draft Burners. — Many large kerosene lamps use circular wicks. They have an open tube extending from the top of the burner down through the center of the bowl to the open central portion of the base. The rim of the base is perforated so that a current of fresh air can readily pass upward through the tube to supply the inside of the flame.

There are, of course, perforations through the sides and bottom of the burner to supply fresh air to the

Fig. 7. — Center-draft lamp.

outside of the flame. Such lamps are known as center draft lamp*. (Fig. 7.)

III. EVAPORATION, BOILING TEMPERATURE, AND DISTILLATION

Evaporation

ii. Need of New Terms. — We have thus far been studying the burning of paraffin in the candle and of kerosene in the ordinary lamp. Gasoline has often been used for producing artificial light where gas or electricity is unobtainable. Gasoline lamps of many different kinds have been made and in many homes gasoline is used both for lighting and cooking. With this increase in its use people have discovered that gasoline is also one of man's most dangerous servants if not carefully and properly handled. Many accidents have resulted from its use. Most people who use gasoline know that it is more dangerous than is kerosene. But many people are using gasoline every day who do not know just why it is dangerous, what to do with it, or how to handle it to make it a safe and obedient servant.

We should like to study gasoline; we hope to learn its nature and how to handle it. Before we can do so, how r ever, we must know the meaning of certain terms and how to use them correctly. We must know where gasoline comes from and its relation to kerosene. These topics w T ill be studied next.

12. Evaporation. — We are all aware that damp clothes hung upon the line at any time except when it is raining soon lose the water they contain and become dry. We wash our porches and floors and soon they are dry. We place a basin of water in an exposed place and the water soon disappears.

The explanation is that the water changes from a liquid to a gas, or vapor, and escapes into the air. This process by which water changes from its liquid form into a gas, or vapor, we call evaporation.

The washerwoman also knows that on some days the clothes will dry much more rapidly than on others. We know that the freshly washed floors will dry more quickly if we open the doors and windows or build a fire in the furnace or stove. The farmer has learned to tell very accurately, by watching the weather, whether or not the fields and roads are drying rapidly. The question arises : What are the conditions under which evaporation takes place most rapidly? This question can best be answered by experiment.

Exercise 6. — Effect of Extent of Surface on Rate of Evaporation

Fill a small drinking cup about half full of water, measuring exactly the amount used. Again measure the same amount of water, and place it in a large, shallow pan or basin. Set the cup beside the pan in a safe place where it will not be disturbed. The two vessels should have the same temperature and be exposed to the same air currents. Examine them daily and note the rate of evaporation in each, till one is dry. Measure the amount of water remaining in the other.

Which is dry first? What conclusion do you draw regarding the effect of extent of surface on evaporation?

Exercise 7. — Effect of Temperature on Rate of Evaporation Place one drinking cup containing a measured quantity of water on or near the stove or radiator. The water should not boil, but be kept warm. Place another cup of the same size and shape containing the same amount of water in a cooler place. Watch these two cups till one is dry. Draw a conclusion regarding the effect of temperature on the rate of evaporation.

Exercise 8. — Effect of Air Currents on Rate of Evaporation

Place two drinking cups of the same size and shape, each about one-half full of water (measuring amounts accurately), side by side in an open window or in some other position where the wind can sweep past them. Turn a large, 2-qt. cup or a small pail over one of the cups of water. Examine the cups of water daily and note which suffers the greater evaporation. What is your conclusion ?

Exercise 9. — Rate of Evaporation Varies with Different Liquids

Place two drinking cups of the same size and shape side by side in some safe place. Fill one about half full of water, and place in the other the same amount of alcohol or gasoline. (Caution. — It is dangerous to leave gasoline in a closed room. It should be in the open air and no flames should be brought near it.) Note which evaporates more rapidly. Draw your conclusion.

Exercise 10. — Effect of Evaporation on Temperature

Let a few drops of alcohol or gasoline fall upon the back of your hand. Does it produce the sensation of heat or cold? Wrap a small piece of cotton cloth around the bulb of the thermometer and tie with a cord or thread. Take the reading of the temperature. Drop a few drops of alcohol or gasoline upon the cloth. Watch for a change in temperature. Repeat the experiment. Does the thermometer record the lowest temperature when the liquid is first dropped upon it or a little later? How do you account for this fact ? Wet your hand and hold it out of the window where the wind can strike it. What is the sensation?

Draw a conclusion regarding the effect of evaporation upon temperature.

Hunters usually wish to approach their game from the leeward side, that is, so that the wind will blow from the game toward the- hunter. Why do they wish to do so ? In order to tell the direction of the wind when it is too light to be observed readily by ordinal means the hunter often wets one finger at his mouth and then holds it high above his head where the wind can strike it. Try the experiment when you are out of doors and decide how it is that this tells the direction of the wind.

Why do we often feel chilly if we sit down with damp clothing on? Why does fanning one's self produce the cooling effect that it does ? Is the cooling effect of fanning increased or decreased by the fact that one has been perspiring freely ?

In regions having a dry, hot, windy climate like Arizona and New Mexico, it is found that butter can be kept hard and sweet for long periods simply by setting the dish containing the butter into a larger dish containing water and then spreading over the butter a piece of soft absorbent cloth, such as a clean towel, so that its corners and edges dip down into the water. The butter keeps sweet longer if placed where the wind strikes it. Explain.

In the same regions drinking water is generally kept during the summer months in a large, porous, earthen vessel called an olla (o'-ya), which is hung out of doors, usually under a porch or tree. The olla being porous, its outer surface is constantly covered with a. film of water. Evaporation taking place over so large a surface cools the water within the vessel far below the temperature of the surrounding air.

13. Laws of Evaporation. — From these and similar experiences we draw the following conclusions :

I. The rate of evaporation from any given amount of liquid increases when the exposed surface is increased.

II. Increasing the temperature of a liquid increases the rate of its evaporation.

III. The rate of evaporation is increased by the continual removal of vapor above the surface of the liquid.

IV. Some liquids evaporate much more rapidly than do others.

V. Evaporation of a liquid always produces a cooling effect upon surrounding bodies.

Temperature and the Thermometer

14. Temperature. — We are all familiar with the common use of the term temperature. By it we mean the hotness or the coldness of a body. On a cold day we say that the temperature is low ; on a warm day we say it is high. We can generally tell when one body is warmer than another if we feel of the two bodies at the same time. We cannot, however, be certain of our judgment. Different substances feel to be of different temperature when they are in fact of the same temperature. The bare-footed boy knows this to be true. A piece of iron and a piece of wood lying side by side on a hot day will be of the same temperature. Will they feel so?

Which feels the warmer? What would be the case on a cold day? Which would then feel the colder?

If at the close of a long ride on a very cold, windy day we were to step into an unheated room we would at once say that the room was warm. If we were to remove our wraps and sit down we should soon find, however, that the room was really cold.

The truth is we cannot depend upon the appearance of objects, nor upon our sensations of heat and cold, to tell us the temperature of surrounding bodies. In all our work we shall be obliged to use an instrument especially constructed for this purpose, the thermometer.

15. The Principle of the Thermometer. —

Exercise 11. — How Heat Affects the Thermometer

Fill a small flask with water. Fit a glass tube, 12 or 15 in. long, into a one-hole rubber stopper. Press the stopper down tightty into the flask. This should force the water well up into the tube.