elements in rows and columns. In the
rows, the elements are placed in order of
their atomic number. The columns form
groups of elements that have similar
chemical properties. The periodic table
helps chemists think about the elements
and their properties.
..More to explore
Atom • Matter
Chemistry
Chemistry is one of the major branches
of science. People who work in chemistry
are called chemists. Chemists study
the substances that make up matter—
everything that takes up space in the
universe. They also study the changes
that take place when substances are
combined. These changes are called
chemical reactions.
In addition, chemists create new substances.
They have made plastics, fibers,
The periodic table groups elements by their properties.
86 Chemistry BRITANNICA STUDENT ENCYCLOPEDIA
building materials, medicines, and many
other substances that are useful in everyday
life.
Elements and Compounds
The basic substances that chemists study
are called chemical elements. Each element
is made up of tiny particles, or
bits, called atoms. Chemical reactions
involve atoms or groups of atoms. When
two or more atoms combine, they form
a molecule.
Each element has certain properties, or
characteristics. When elements are
combined, they form a new substance
with its own properties. A substance
formed in this way is called a
compound. There are a little more than
100 elements. But there are millions of
compounds.
Fields of Study
Chemistry is a complex subject with
many fields of study. For example,
organic chemists deal only with compounds
of the element carbon. Physical
chemists measure the way that substances
change during chemical reactions.
Biochemists study chemical
processes that happen in living things.
History
People first studied chemistry as a science
in the 1600s. In 1661 a British
scientist named Robert Boyle described
chemical elements as simple, basic substances.
In the 1770s a French chemist
named Antoine Lavoisier helped to
explain chemical reactions.
In the early 1800s a British chemist
named John Dalton found that each
element has its own kind of atom. Other
chemists discovered many new elements
during the 1800s.
Later chemists continued to make discoveries
about atoms. For example, they
learned that atoms are made up of even
simpler particles.
#More to explore
Atom • Chemical Element • Matter
• Molecule
Cherokee
The Cherokee are the largest Native
American group in the United States.
They once lived around the Great Lakes.
After battles with other tribes, they
moved to what is now the southeastern
People called
alchemists
worked with
chemicals
before chemistry
became a
science. They
tried to
change lead
into gold. They
failed, but they
learned about
elements in the
process.
Students of chemistry learn about the substances
that make up matter. They also
study the changes that take place during
chemical reactions.
BRITANNICA STUDENT ENCYCLOPEDIA Cherokee 87
United States. Today they live mostly in
Oklahoma.
The Cherokee traditionally grew corn,
beans, and squash. They hunted deer,
bear, and elk. They lived in log cabins
with roofs made of bark.
Europeans arrived in Cherokee territory
in the middle of the 1500s. By that time
the Cherokee lived in the Southeast.
Over the next 200 years the Cherokee
lost much of their land and power to
white settlers.
After 1800 the Cherokee took on some
parts of white culture. They formed a
government based on that of the United
States. A man named Sequoyah created
a writing system for the Cherokee language.
Most Cherokee learned to read
and write. Whites called the Cherokee
one of the Five Civilized Tribes, along
with the Choctaw, the Seminole, the
Chickasaw, and the Creek.
In the 1830s gold was discovered on
Cherokee land in Georgia. Georgia officials
and the U.S. government forced the
Cherokee to leave their land and march
west. About 4,000 Cherokee died on the
journey, which is called the Trail of
Tears.
Most Cherokee settled in what is now
northeastern Oklahoma. Their descendants
still live there. Some Cherokee live
in western North Carolina. They are
descendants of Cherokee who escaped
into the mountains in the 1830s. In the
late 20th century there were more than
280,000 Cherokee living in the United
States.
#More to explore
Chickasaw • Choctaw • Creek • Native
Americans • Seminole • Sequoyah • Trail
of Tears
Cherry
Cherries are small, round fruits that can
be sweet or sour. They grow on trees
Cherokee dancers perform at a Native
American celebration.
Cherries grow on stems that
hang from tree branches.
88 Cherry BRITANNICA STUDENT ENCYCLOPEDIA
that are common in North America,
Europe, and eastern Asia.
Different types of cherry tree produce
sweet cherries and sour cherries. Sweetcherry
trees are large, reaching heights
up to 36 feet (11 meters). Their fruit is
usually round or heart-shaped. Sweet
cherries vary in color from yellow to red
to nearly black. People eat sweet cherries
fresh or canned.
Sour-cherry trees are smaller than sweetcherry
trees. They are usually less than
16 feet (5 meters) tall. Sour cherries are
round and smaller than sweet cherries.
They are usually dark red. Sour cherries
