Steven Boone - College Chemistry

This second edition of College Chemistry is written for the beginning college chemistry student and may be used as a supplement to any comprehensive general chemistry textbook. The content is nearly the same as that found for a typical two-semester general chemistry sequence. Many students will find that the alternate explanations, the complete solutions to many exercises, and the Test Yourself problems pro-vided herein will enhance the learning process.

This book begins with an introduction to chemistry (chapter 1) and how measurements are used in scientific inquiry (chapter 2). These chapters are followed by discussions of chemical substances (chapter 3), stoichiometry (chapter 4), and chemical reactions (chapter 5). The first of the physical states of matter is gases (chapter 6) and liquids and solids (chapter 12) are discussed later in the book. Chemical thermodynamics is split into thermochemistry (chapter 7) and free energy, entropy, and equilibria (chapter 18). The atomic structure of the atom and quantum theory (chapter 8), periodic properties of atoms (chapter 9), is followed by two chapters on bonding: ionic and covalent bonding (chapter 10) and the bonding theories and molecular shape (chapter 11). The next five chapters develop an understanding of the physical properties of solutions (chapter 13), chemical kinetics (chapter 14), chemical equilibria (chapter 15), and aqueous equilibria (chapters 16 & 17). The final two chapters comprise a discussion of electrochemistry (chapter 19) and nuclear chemistry (chapter 20).

I appreciate the contributions and suggestions of Professor Drew Wolf and Professor Christopher Exstrom. A sincere and special thanks to Ms. Tere Stouffer and Mr. Fred N. Grayson, of American Book Works Corporation. Finally, there was considerable love and support from Sadie, my wife, and Rachel, my daughter.

Steven R. Boone, Ph.D.

C hemistry is one of the three major areas in science, along with biology and physics. In this chapter, we will first propose a definition for chemistry and discuss its scope. Then, we will turn our attention to the principal concern of chemistry: matter.

1.1 WHAT IS CHEMISTRY?

It is important to understand the definition of chemistry in its historical context.

ChemistryDefinition, Practitioners, and History

Chemistry is the science of matter and the changes it undergoes. The main focus of chemistry is matter. All objects in the world are types of matter.

A chemist is a person who studies the composition, structure, and properties of matter and seeks to explain the changes that matter undergoes.

Modern chemistry grew out of the pseudoscience called alchemy . Alchemists searched for methods to convert base metals to gold. Robert Boyle (16271691) was one of the first scientists to suggest that ideas and thoughts about matter must be supported by reproducible experiments. Antoine Lavoisier (17431794) is credited with being the father of modern chemistry because of his pioneering experiments on the properties of matter.

Matter, Mass, and Energy

Matter is anything that has mass and occupies space. The mass of an object is a measure of the amount of matter it has. Closely related to matter is energy. Thus, chemistry also considers the relationship of matter and energy.

Energy is the capacity to do work, or more simply, the capacity to change something.

1.2 MATTER AND ITS PROPERTIES

This section focuses on the definition of chemistry, which involves matter and the changes matter undergoes.

Composition and Structure

Composition refers to the identity and amount of the components of matter. Structure describes the physical arrangement of its particles (atoms, ions, or molecules). Some types of matter have a highly organized structure, while others are random.

Physical Properties and Changes

Chemists distinguish one type of matter from another by identifying their properties, just as people are differentiated by observing their physical appearance and personality traits. Properties are classified as being either physical or chemical. Physical properties are characteristics of a particular type of matter that can be measured without changing its composition. Density, color, melting point, boiling point, physical state, heat conductivity, and electrical conductivity are examples of physical properties of matter.

If a change occurs in the physical properties of a sample of matter without a change in composition, a physical change occurs. After such a change, the same type of matter is present but has a different set of physical properties. Changes in shape, size, and physical state are other examples of physical changes.

Chemical Properties and Changes

A chemical property describes what happens to one type of matter when it changes composition. When the matter changes its composition, a chemical reaction or chemical change occurs. Therefore, chemical properties describe the chemical reactions that matter undergoes. For example, a chemical property of gasoline is that it burns (undergoes oxidation) when ignited. Gasoline is a liquid mixture of carbon-hydrogen compounds.

Exercise 1.1

Classify each of the following as a physical property, physical change, chemical property, or chemical change: (a) A blue solid, (b) an explosive liquid, and (c) a solid changes directly to a vapor without becoming a liquid.

Solution 1.1

(a) A physical property, because it is a characteristic of a solid without reference to any other substance. (b) A chemical property, because explosive describes a chemical change that the liquid undergoes. (c) A physical change, because the solid does not change composition.

1.3 CLASSIFICATION OF MATTER

Samples of matter can be classified as being either pure substances or mixtures.

Pure Substances

Pure substances (or, simply, substances ) have a constant composition, cannot be separated into simpler components by physical methods, and undergo state changes at a constant temperature. Examples of pure substances include gold, copper, and carbon dioxide. Pure substances can be further subdivided into elements or compounds.

Mixtures

A mixture results when pure substances that do not react are combined. Mixtures have a variable composition, can usually be separated by physical methods, and undergo state change over range of temperatures. Mixtures can either be homogenous (those with one phase) or heterogeneous (those with two or more phases). Ocean water, concrete, air, and asphalt are four examples of mixtures.

Elements

Elements are the basic units of matter. All of the types of matter contain elements. About 115 different elements have been identified. Of these elements, 92 occur in nature, and the remaining elements are synthetic. At 25C, 102 elements are solids, 2 are liquids, and 11 are gases.

Periodic Table of Elements

The symbols of the elements are found in the Periodic Table. This table is one of the most important tables in chemistry. Each element is located in a horizontal row called a period and in a vertical column called a group (sometimes called a family ). Each period is numbered consecutively from 1 to 7. Each group of elements is assigned a Roman numeral and a letter. It has been recommended by the International Union of Pure and Applied Chemists (IUPAC) that the groups be numbered consecutively from 1 to 18. Thus, two numbering systems are now used.