Chemistry: The Molecular Nature of Matter and Change – Standalone book 7th Edition

Book Preface

Maybe you’re taking this course because chemistry is fundamental to understanding other natural sciences.
Maybe it’s required for your medical or engineering major. Or maybe you just want to learn more about the impact of chemistry on society or even on a personal, everyday level. For example, were you awakened today by your alarm clock? In chemical terms, the sound of the alarm was created when molecules aligned in the liquid-crystal display of your clock and electrons flowed to create a noise. You might have thrown off a thermal insulator of manufactured polymer (blanket) and jumped in the shower to emulsify fatty substances on your skin and hair with purified water and formulated detergents. Perhaps you next adorned yourself in an array of pleasant-smelling pigmented gels, dyed polymeric fibers, synthetic footwear, and metal-alloy jewelry. After a breakfast of nutrient-enriched, spoilage-retarded carbohydrates (cereal) in a white emulsion of fats, proteins, and monosaccharides (milk) and a cup of hot aqueous extract containing a stimulating alkaloid (coffee), you probably abraded your teeth with a colloidal dispersion of artificially flavored, dental-hardening agents (toothpaste), grabbed your portable electronic device containing ultrathin, microetched semiconductor layers powered by a series of voltaic cells (laptop), collected some objects made from processed cellulose and plastic, electronically printed with light- and oxygen-resistant inks (books), hopped in your hydrocarbon-fueled, metal-vinyl-ceramic vehicle, electrically ignited a synchronized series of controlled gaseous explosions (started your car), and took off for class!

But the true impact of chemistry extends much farther than the commercial products of daily life. The truth is that the most profound biological and environmental questions ultimately have chemical answers: How does an organism reproduce, grow, and age? What are the underlying explanations for health and disease? How can we sustain a planetary ecosystem in which plant, animal, and human populations thrive? Is there life on other worlds?

So, no matter what your reason for studying chemistry, you’re going to learn some amazing ideas. And, this course comes with a bonus for developing two mental skills. The first, common to all science courses, is the ability to solve problems systematically. The second is specific to chemistry, for as you comprehend its ideas, you begin to view a hidden reality, one filled with incredibly minute particles moving at fantastic speeds, colliding billions of times a second, and interacting in ways that allow your brain to translate fluxes of electric charge into thoughts and that determine how all the matter inside and outside of you behaves. This chapter holds the keys to unlock and enter this new world.
in this chapter . . . We discuss some central ideas about matter and energy, the process of science, units of measurement, and how scientists handle data.
-We begin with fundamental concepts about matter and energy and their changes.
-A brief discussion of chemistry’s origins, including some major missteps, leads to an overview of how scientists build models to study nature.
-We examine modern units for mass, length, volume, density, and temperature and apply systematic chemical problem solving to unit conversions.
-We see that data collection always includes some uncertainty and examine the distinction between accuracy and precision.

SOME FUNDAMENTAL DEFINITIONS

A good place to begin our exploration of chemistry is to define it and a few central concepts. Chemistry is the study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes. Matter is the “stuff ” of the universe: air, glass, planets, students—anything that has mass and volume. (In Section 1.4, we discuss the meanings of mass and volume in terms of how they are measured.) Chemists want to know the composition of matter, the types and amounts of simpler substances that make it up. A substance is a type of matter that has a defined, fixed composition.

The States of Matter

Matter occurs commonly in three physical forms called states: solid, liquid, and gas. On the macroscopic scale, each state of matter is defined by the way the sample fills a container (Figure 1.1, flasks at top):
•A solid has a fixed shape that does not conform to the container shape. Solids are not defined by rigidity or hardness: solid iron is rigid and hard, but solid lead is flexible, and solid wax is soft.
•A liquid has a varying shape that conforms to the container shape, but only to the extent of the liquid’s volume; that is, a liquid has an upper surface.
•A gas also has a varying shape that conforms to the container shape, but it fills the entire container and, thus, does not have a surface.
On the atomic scale, each state is defined by the relative positions of its particles (Figure 1.1, circles at bottom):
•In a solid, the particles lie next to each other in a regular, three-dimensional array.
• In a liquid, the particles also lie close together but move randomly around each other.
•In a gas, the particles have large distances between them and move randomly throughout the container.