Snakes can see very well, too. Snakes
flick out their tongue to “taste” the air,
which gives them information about
their surroundings. Snakes do not have
vocal cords. This means that they are
voiceless. However, they can make a
hissing sound by sending air through an
opening in the mouth.
A snake’s color can help protect it from
enemies. Some snakes blend in with
their surroundings. For example, many
tree snakes are bright green and resemble
vines. The bright colors of some snakes
warn attackers that they are poisonous.
Snakes are cold-blooded animals. This
means that their body temperature
changes along with the temperature of
their surroundings. To survive cold seasons,
some snakes go into hiding places
and become inactive for months at a
time. This is like hibernation in mammals.
Movement
Most snakes move by pushing the scales
on the underside of their body against
the ground. The body moves in a series
of S-shaped loops. Some large snakes,
such as the boas, move in a straight line.
They inch their body forward like a caterpillar
does. Other snakes move by
folding and unfolding like an accordion.
Many desert snakes use a movement
called sidewinding. They throw their
body upward and sideways across the
sand.
Life Cycle
Most snakes live alone for most of the
year. Some kinds gather for mating or
hibernation. Most snakes lay eggs, but
others give birth to live young. The
number of young varies from about 3 to
more than 50. At birth, baby snakes
look like adult snakes. Snakes kept by
people can live more than 30 years.
Snakes in the wild do not live as long.
A black-and-yellow mangrove snake sticks
out its forked tongue. A snake uses its
tongue to gather information about its surroundings.
114 Snake BRITANNICA STUDENT ENCYCLOPEDIA
Snakes and Humans
Some people think snakes are scary and
dangerous. However, a snake bites a
human only when it is frightened or
threatened. Plus, snakes eat rats and
mice, which most people consider to be
pests. People hunt snakes as a source of
clothing and food. Some snakes are captured
and sold as pets.
#More to explore
Anaconda • Boa Constrictor • Cobra
• Lizard • Python • Rattlesnake • Reptile
• Sea Snake • Viper
Snow
Tiny crystals of ice that fall to Earth are
called snow. A crystal is a solid substance
that has flat surfaces and sharp corners.
Snowfall is made up of both single ice
crystals and clumps of ice crystals. The
clumps are called snowflakes.
How Snow Forms
Snow is formed high in the clouds from
water vapor, which is water in the form
of gas. If a cloud is cold enough, the
water vapor freezes to form ice crystals.
At temperatures between about .40° F
(.40° C) and 32° F (0° C), water vapor
crystallizes around bits of dust in the
cloud. At lower temperatures, water
vapor freezes directly into ice crystals.
The ice crystals can stay up in the
clouds. Or, if they are heavy enough,
they can fall to the ground. As they fall
they can clump together with other ice
crystals to form snowflakes. One snowflake
can contain as many as 100 ice
crystals. But some single ice crystals fall
as snow, too.
Snowflake Shapes
The way that ice crystals join together
gives every snowflake a unique design.
Even so, most snowflakes have six
points or six sides. They form seven
basic shapes: stars, needles, dendrites
(having branches), plates, columns,
A green mamba hatches from its
egg. Baby snakes look like small
adult snakes.
A layer of snow covers the ground in a
mountainous region. Like rain, snow is
made of water. But the water in snow is frozen
into crystals of ice.
BRITANNICA STUDENT ENCYCLOPEDIA Snow 115
columns capped with plates, and
irregular (damaged). What shape a
snowflake takes depends on the
temperature and the amount of
moisture in the cloud.
Where Snow Falls
Snow falls in many places that get cold
weather, mainly during winter. In areas
near the North and South poles, snow
covers Earth year-round. Near the equator,
snow falls only in the highest mountain
regions.
Effects of Snow
Snow greatly affects climates and living
things. A cover of snow on the ground
helps to keep the air cold. This happens
because snow reflects, or bounces back,
most of the sun’s heat. However, a snow
cover can also protect small plants from
the effects of severe cold. When snow
melts in the spring, it provides freshwater
for people and animals. But if snow
does not melt for years, it may form
huge slabs of ice, called glaciers.
#More to explore
Climate • Cloud • Crystal • Glacier
•Water
Soccer
Soccer is the world’s most popular team
sport. In most parts of the world the
game is called football or association
football. Both men and women play
soccer in schools, clubs, and on national
and professional teams. In a soccer game
two teams compete to score more
points, which are called goals. The players
move the ball around a rectangular
field, usually by kicking it. A team scores
when it sends the ball into the opposing
team’s goal.
The World Cup soccer tournament is
the world’s most popular sports event.
Every four years teams from many countries
compete for theWorld Cup.
Playing Area and Equipment
Soccer fields vary in size. A field should
