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Section 1: Introduction
Figure 1-1. Bioluminescent Lobate Ctenophore (comb jellyfish)
Bioluminescent organisms like this jellyfish produce light from chemical reactions within their tissues. Others carry light-producing bacteria within their bodies.
Chemicals are the building blocks of our planet and of the living systems that inhabit it. The science of chemistry analyzes the structure of matter, its properties, and how chemicals combine and change. It enables us to understand countless processes that take place naturally around us—for example, how rocks break down slowly into soil, or why volcanic eruptions can affect weather patterns and air quality across large areas.
Chemistry is also central to numerous functions and characteristics of living organisms. Some chemical processes are common across many species, such as digestion—breaking down food and extracting its nutrients. Others are more specialized and only occur in certain types of organisms. As an example, some bacteria, insects, algae, jellyfish, and other organisms (mainly aquatic and almost all invertebrates) are bioluminescent: They can produce visible light from chemical reactions within their tissues. (Figure 1-1)
Long before humans began to study chemistry, or even formed the concept of science and scientific inquiry, they were using basic chemistry techniques to improve their daily lives. Setting fuel on fire is a chemical process that generates heat. Cooking food over fire causes chemical changes in the food; so do other processes that have been widely used for thousands of years, such as leavening and fermentation (using chemical reactions to make baked goods rise or convert sugars into alcohol). Human civilization progressed from the Stone Age through the Bronze and Iron Ages as humans learned to smelt these metals and cast them into tools and weapons—skills that required an increasingly sophisticated understanding of the properties of metals and how they could be manipulated.
Figure 1-2. Interior of a Laboratory with an Alchemist
Painting of an alchemist from the Chemical Heritage Foundation's "Transmutations" exhibit.
© Chemical Heritage Foundation, oil on canvas by David Teniers II, 17th century.
Scholars started thinking analytically about chemistry thousands of years ago. Greek philosophers tried to identify the smallest unit of matter and theorized about which elements were the core ingredients of all other substances. Through the Middle Ages and Renaissance, as chemical scholarship shifted first to the Arab empire and then west to Christian Europe, it blended several ways of thinking. On a practical level, skilled craftspeople developed standard procedures for making paints, medicines, inks, dyes, and many other products used widely in daily life. At the same time, an evolving discipline called "alchemy" pondered broader philosophical challenges that often were framed in religious terms: What were the highest forms of matter? Could one material be transformed into another that was purer? And in doing so, could humans also purify themselves, perhaps even achieving eternal life? (Figure 1-2)
In the 1500s and 1600s, scholars' approach to chemistry started to change and became increasingly rooted in observation, experimentation, and evidence, rather than in religious or philosophical beliefs. Chemistry evolved into an empirical, laboratory-based science in the 18th and 19th centuries, with investigators studying chemical processes systematically, formulating laws about properties of matter, and disproving earlier beliefs. By the late 19th century, chemistry was an established scientific discipline that was contributing practical knowledge to many sectors of modern industrial life. And researchers were pursuing a new goal: penetrating the atom.