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SUGGESTIONS CONCERNING EXPERI
Each observant person is constantly noting occurrences in nature which he would like to have explained to him. A flying kite leads us to ask how it is made to fly. Boiling water in a kettle lifts the lid which covers it, and we want to know what causes the lid to rise. The tender stem of a plant pushes up through gravelly or hard-packed soil, crowding the pebbles and soil out of the way, and we ask how the delicate shoot, still uninjured, can move such solid bodies. A colony of ants makes its home in a field of corn; the corn is soon retarded in its growth, and we want to know what is taking place. A pupil visits a friend who is ill, and later the visitor may have the same disease as that which affects the friend. What has occurred ? Many such questions concern our daily lives, and we are more intelligent and more efficient persons when we can answer some of these questions correctly.
There are two good ways of securing answers to our questions. One way is to ask persons who know about these matters or to read what they may have written. The other way is to study the occurrence by means of observation and experiment, thus trying to make the occurrence itself help to answer the question regarding it. It is the purpose of these outlines to use the latter method in answering some important questions.
To secure the greatest good from an experiment it is necessary (1) to watch the way in which the experiment is performed; (2) to select the facts shown by the experiment; and (3) to explain these facts, if an explanation can be made. When you have performed an experiment and discussed it, write your final statement as if your notes were intended to be read by a person who knows nothing about the experiment. In all cases make sure that your work is brief, neat, and clear in its presentation of the facts.
ELEMENTS OF GENERAL SCIENCE
AIR AS A MATERIAL (I-1) 1
The problem. Most of the time we are quite unconscious of the air; in fact, we usually ignore its existence. The condition of the air is a matter of importance to all. It determines whether our sports shall be tennis, golf, and baseball, or coasting and snowballing; it decides whether we shall swim or skate; it affects the kind of clothing we shall wear, the food we shall eat, and the social activities in which we shall engage. It levies a tax for coal at one time and for ice and electric fans at another. How can we find out if air is a real material which we can readily recognize?
What to use. Ring stand, clamp, glass cylinder of about one quart capacity, two-hole rubber stopper, wooden rod, glass tube two feet long, glass plug made from ordinary glass tubing, and the upper half of an eight-inch test tube. What to do. 1. Assemble the apparatus as shown in figure 1.
Throughout the manual the problems are numbered serially. Immediately following the title of a problem two numbers appear in brackets. The first of these figures indicates the chapter in the text to which the materials of the problem relate, and the second figure indicates the number of the problem which relates to that chapter. For example, following the title of problem 32 are the numbers (XI-1), which means that this is the first problem relating to the materials of Chapter XI. 2 In appendix, p. 177, directions are given for work with glass tubing.
2. Hold the open end of the test tube downward and press it slowly to the bottom of the water in the cylinder. Notice the level of the water inside of the tube.
3. Slowly raise the mouth of the tube to the level of the water. 4. Repeat 2, but release the rod when the tube is at the bottom
of the cylinder.
5. Substitute a glass tube for the wooden rod and repeat 2 and 3 while holding the finger on the end of the glass tube.
6. Repeat 4, using a glass tube instead of the wooden rod.
7. Answer the questions in the following paragraph.
Questions. How high in the test tube does the water rise? Does this vary at different depths ? What fact is shown here? What fact is shown in 4 ? Describe the changes which occur in 6. What conclusions regarding the air does this experiment enable you to make ?
Suggestions for report. After a class
discussion of the answers to the questions Fig. 1
given above, write a correct statement for
each question. Reference work. Make a list of all the illustrations of which you can think to show that air is a material and that it occupies space. Read sections 1 to 5 of " Elements of General Science” (Revised Edition) by Caldwell and Eikenberry."
Optional problems. By means of the apparatus shown in figure 1, and a piece of rubber tubing to fit the glass tube, show how a diving bell works.
1 All text citations throughout this manual are to the text here cited, and the name of the text will not be repeated in further citations.