http://www.ck12.org Chapter 1. Introduction to Chemistry
study of living things. Geology is the study of the Earth and the rocks and minerals of which it is comprised. In
this text, you will learn about the field of chemistry.Chemistryis the study of the composition of matter and the
changes that matter undergoes.Matteris anything that has mass and takes up space. Virtually everything around
us is matter, including both living and nonliving things. Chemistry affects nearly everything we see and every action
we take. Chemistry explains why the leaves of deciduous trees turn from green in the summer to various shades
of red and yellow in the autumn (Figure1.1). Chemistry explains why milk that is left in the refrigerator for too
long turns sour. Chemistry explains why certain pollutants called chlorofluorocarbons have done lasting damage to
the ozone layer of our planet. Chemistry is very much a central, foundational science, and a basic knowledge of
chemistry is essential for students who are pursuing studies in biology, geology, environmental science, medicine,
and many other subjects.
FIGURE 1.
Chemical reactions in the leaves of decid-
uous trees cause them to change color
from green to red, orange, or yellow be-
fore dropping to the ground.Chemists are tasked with looking at the world in two ways, often simultaneously. The two worlds of the chemist are
the macroscopic world and the microscopic world.Macroscopicrefers to substances and objects that can be seen,
touched, and measured directly.Microscopicrefers to the small particles that make up all matter. Chemists must
observe matter and do experiments in the macroscopic world and then use their observations to make generalizations
and propose explanations that are microscopic in nature. For example, anyone can observe the physical change in
appearance that occurs as an iron object rusts, such as a tractor that is left outside for a long enough period of time.
However, a chemist looks at the rusting tractor and thinks about what is going on with the individual atoms that make
up the iron and how they are changing as a result of exposure to rainwater or oxygen in the air. Throughout your
study of chemistry, you will often need to switch back and forth between the macroscopic and microscopic worlds.
Alchemy
Chemistry is a subject that has its roots in the ancient tradition known as alchemy, from which it derives its name.
Alchemy was a combination of philosophy and science that had both practical and mystical aspects. The goals of
alchemy were varied and difficult to summarize. In many ways, the alchemists sought to achieve perfection, through
such actions as the pursuit of the philosopher’s stone and the elixir of life (Figure1.2). The philosopher’s stone, it
was believed, was a substance that was capable of being used to turn base metals (such as lead) into gold. It was also
believed that it could be used to achieve rejuvenation and perhaps immortality. While alchemists did not ultimately
succeed in these quests, their work provided the foundation for the modern study of chemistry.
Alchemists laid the groundwork for many chemical processes, such as the refining of ores, the production of