JOY OF CHEMISTRY -- PART 1 (TO BE CONTINUED)

Cobb, Cathy and Fetterolf, Monty L.  The Joy of Chemistry: The Amazing Science of Familiar Things.  Amherst, New York: Prometheus Books, 2005.

This book is 393 pages in length (paperback version published by Prometheus Books).

This book is written to entice anyone interested in conducting their own experiments at home, with or without any advanced background in chemistry.  The activities described her make use of materials and chemicals that can be purchased in regular grocery stores and hardware stores.  As the author said, the experiments can be done in the kitchen, garage, or outside making use of an “adult” chemistry set derived from the kitchen or the tool box.  Unlike many chemistry sets for sale, a bonus of the book is that it gives some background information and explanations in addition to the step-by-step procedure.  In addition, many chapters contain copious detailed historical information as in Chapter 1 recounting the discovery of the electron.

The book starts off with some safety tips, important even though the chemicals and equipment used are of the household type.  It then provides a shopping list of these chemicals and materials.  Lastly, it provides some instructions on how to make up solutions that cannot be purchased using household substances:  for making copper (II) sulfate, iron (III) acetate, and purple cabbage indicator.

In its introductory demonstration, it gives instructions on how the reader might carry out his or her first “bang and splat” activities.  For the bang activity (bottle rocket), the author describes how to generate carbon dioxide gas fast and furious in a loosely corked plastic bottle to generate enough pressure to turn the cork into a projectile (must be done outside).  Carbon dioxide is generated through the reaction of baking soda or sodium bicarbonate and vinegar.  The splat activity involved making a semi-liquid homogeneous mixture of cornstarch and water.  The resulting “oobleck” (in reference to a Dr. Seuss book) has properties of both solid and liquid depending on what forces it is subjected to (fast or slow pulling forces).

PART I

INTRODUCTION: Theory, Octaves, and Scales

·         “Not unlike music and literature, chemistry is described in terms of its elements and has a theory based on fundamental principles.”

·         “Chemists think in octaves too” is a reference to the octet rule that governs electron arrangement and behavior within an atom.

NOTE: Demonstration instructions are copied verbatim from the book to avoid mistakes and inaccuracies in the steps.

Demonstration 1: Water Witch

Take a plastic spoon and rub it in your hair or on a sweater until the spoon acquires a static charge, as evidenced by the attraction of the spoon for the hair or fibers on the sweater.  Turn on a faucet so that there is a very thin stream of water.  Hold the spoon close to the water and you will see a stream of water bend. 

[My variation:  Have two burets, one with water the other with a nonpolar liquid.]

What happened?  Electron transfer from hair or cloth to plastic material which has a stronger attraction for electrons causes the plastic to acquire a negative charge.

CHAPTER 1:  Electrons and Atoms, Elephants and Fleas

In this chapter the author describes the smallness of the atoms and sub-atomic particles and presents the difficulties of our inability to use our sensual and tactile abilities to study it.  Instead, scientists have to look for secondary effects and infer their causes.  A good quote from Rutherford to Chadwick illustrating this point:  “How could you find the Invisible Man in Piccadilly Circus?...[B]y the reactions of those he pushed aside.”

Some notes on the discovery of the electron:

J. J. Thomson is well-known for having first detected the existence of this particle whose amount of charge he was able to measure by the strength of the magnetic field used to bend a beam of these particles.  “By consensus, electrons were assigned a negative charge.”

It was Jean Perrin however in 1909 that gave a more definitive evidence for the existence of atoms.  He observed the motion of pollen particles in water (subsequently named Brownian motion after the botanist Robert Brown) and attributed it to collisions with moving atoms.  “His observations convinced the scientific community of the validity of the atomic model.”

Discovery of the proton:

In his famous experiment, Rutherford in 1910 fired alpha particles at an ultrathin gold foil and observed some of them bouncing back “as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you”.  Rutherford had discovered the nucleus of the atom.  Henry Moseley was the one, however, to provide the experimental evidence for the existence of the positively charged particles, protons.

Discovery of the neutron:

Because of its neutral charge, it took some time to discover the presence of neutrons, but Chadwick was able to confirm their existence in 1932 by measuring the “rebound of certain radiation from nitrogen and helium and found it corresponded to a neutral particle with about the same mass as a proton”.