Introduction to Understandable Physics
Volume II - Matter, Heat and Waves
by
Book Cover & Preview Text
12-1. Introduction
In the last chapter of Volume I we examined nature on the very large or astronomical scale. In this chapter, we will examine the other extreme at the very small or atomic scale. Having an insight to behavior at the atomic scale is often useful for studying the basic properties of matter, which will be examined in the next few chapters.
Most people understand that matter is made up of extremely small atoms, each of which have electrons orbiting a more massive nucleus. The electron “cloud” of orbits of an atom defines its size, which is measured in units of 10-10 m or angstroms (Å). Probably a majority also know that the nucleus is much smaller in size although it contains most of the mass of the atom, as the electrons have relatively little mass. In fact the nucleus is so small that it is measured in units of 10-15 m or fermis (fm). Also, we may know that atoms have even been imaged in modern times, using instruments such as scanning tunneling microscopes. Even the paths of various individual nuclei have been imaged in bubble chambers at some of the particle accelerator laboratories.
In addition to the above general knowledge about atoms, one should understand how this knowledge became known. How did scientists even begin to find out these things that we almost take for granted? In this chapter, we will review the sequence of the relevant historical discoveries that lead to our present understanding of the nature of atoms. In addition, we will develop some basic relations to deal with the masses and dimensions of atoms.
12-2. Ancient Atomic Concepts and Their Preservation
(500 BC - 1600 AD)
The idea that matter could be composed of atoms goes back about 2500 years, based on our current knowledge. The Greek philosopher Democritus (c460 - 370 BC) of Abdera is normally credited as the first to advance the idea of the atom. He theorized that there were finer and finer parts of matter that should eventually be made up of basic smallest pieces. Such a piece was called an atom after the Greek word atomos meaning undividable. Democritus' theory was controversial and discounted by many as unprovable. In particular, Aristotle (384 - 322 BC), also a Greek philosopher, argued that the idea of atoms was illogical.
The concept of the atom received later attention from Epicurus (341 - 270 BC) of Samos, yet another Greek philosopher, who conducted his school of philosophy in Athens from 306 BC until his death. His ideas on science and religion, as related to happiness, had a strong impact on the Greco-Roman world for hundreds of years; however, although a prolific writer, most of his original works did not survive in tact. Fortunately, a Roman philosophical poet Lucretius (c95 - c55 BC) wrote a six-book poem De rerum natura (On the Nature of Things), which included much of the philosophy of Epicurus, along with his concepts about atoms.
Although Lucretius' poem preserved the idea of atoms, we are not aware that any further significant thoughts emerged about atoms for the next 1500 years. In fact only a single copy of the poem was known to have survived during this period; however, the onset of printing in the fifteenth century lead to its reproduction. Subsequently, Pierre Gassendi (1592 - 1655), a French philosopher, became interested in the Epicurean concepts given in Lucretius's poem, and this lead to a rekindling of the atomic philosophy.
12-3. Scientific Beginnings: Atomic Concepts from Gas Studies
(1600 -1820)
Boyle's Law
Robert Boyle (1627 - 1691), an Irish chemist, was influenced by the atomic concepts promoted by Gassendi. In 1661, he wrote a book entitled The Sceptical Chymist in which he presented the concept of an element. A year later, he was the first to publish a relation describing the behavior of pressure and volume of gases, which had been observed by various scientists as early as 1660. The relation has now become known as Boyle's Law and is given by
pV = B = Constant (for constant temperature and mass) [1]
where p is the pressure of the gas and V is its volume. Here the pressure is the force per unit area that the gas exerts on each of its container walls. Boyle found that the mass of a gas remains the same when a gas is expanded or compressed. Thus, he reasoned that gas must have cavities, behaving somewhat like a sponge when squeezed. The cavities suggest that there are empty spaces between the pieces or atoms (molecules) of a gas.
Formats
Book Details
About the Book
Will Winn has written Introduction to Understandable Physics with the goal of presenting physics concepts in a building-block fashion. In Volume II mathematical tools covered in Volume I are summarized in an Appendix, as a reference for learning the physics. As Volume II builds on the Mechanicsof Volume I, it is expected that the student will have mastered the material of this earlier volume. The present volume begins with a historical review of how the atomic nature of matter was discovered. Then this background is applied in the study of solids, liquids, and gases. Next the kinetic nature of gases is extended to examine heat and temperature concepts for the above states of matter. Following a study of heat transfer modes (conduction, convection, and radiation), thermodynamics is introduced to examine heat engines and the concept of entropy. Next a study of the general nature of waves is appropriate, since a number of wave speeds had already been developed in the preceding examination of mechanics, matter and heat. Finally, these wave concepts are applied to a study of sound, including human response and the nature of music.
Near the end of each chapter a Simple Projects section suggests experiments and/or field trips that may serve to reinforce the physics covered. Some of the experiments are simple enough for students to explore alone, while others benefit from equipment available to physics instructors. When opportune, the text develops relations that are revisited much later in the text. For example, both Chapters 16 and 17 develop the Stefan-Boltzmann radiation law, which is shown to be consistent with the Planck radiation law based on quantum concepts, in Volume IV Chapter 29. Also optional text sections provide students with a deeper appreciation of the subject matter; however they are not required for continuity. Some of these optional topics can be candidates for term projects.
About the Author
Will Winn has enjoyed a 50-yr physics career, which includes various experiences in teaching , pure research, and industrial applications. Early in his career he taught physics at both secondary institutions and universities, namely Cornell and Virginia Commonwealth, and in later years he taught again at University of South Carolina Aiken. Upon receiving his Ph.D. in nuclear physics at Cornell in 1968, he had commenced a post-doctoral appointment at the Washington University Cyclotron facility to conduct research on nuclear energy levels, and he continued this work with another post-doctoral appointment at the MP Van de Graaff accelerator at the University of Rochester. Seeking to apply his background to practical applications, he completed a masters degree program in Nuclear Engineering at University of Virginia in 1974. Then he began his research at the Savannah River Site, which included reactor experiments, nuclear chemistry, non-destructive testing, environmental monitoring, and non-proliferation studies. In 2000 he retired from SRS to teach math and physics at USCA, after which he commenced writing this text. Here, he refined physics notes he prepared for his USCA students, as well as drawing from his career writing experience, which includes over 60 published papers.
Dr. Winn has encountered a wide range of activities related to physics over the years. He has conducted research with university professors, chemists, biologists, geologists, engineers, and other physicists. As a former premed student who switched to physics, he also has had a continuing interest in the physics involved in medical applications. Accordingly, he has a good appreciation for the role of physics in a considerable number of fields, and this has influenced his teaching of students who require an introductory physics course. Furthermore, he has applied this experience to writing Introduction to Understandable Physics.