Water
is a transparent, odorless, tasteless liquid composed of
the elements hydrogen and oxygen. It is a very good
solvent, meaning that many substances can dissolve in it
easily. Water is important to our lives, and without it
we could not live. In fact, there are no living creatures
that can live without water.
There
are four states of matter commonly found in the Universe.
There are solids, liquid, gases, and plasma. There is
also a fifth state of matter, the Bose-Einstein Condensate
which is seen at extremely low temperatures. All matter is
found in these states. Water is one of the few
substances that can easily change into three of the
states, liquid, gas, and solid. Water goes through three
states of matter easily. Ice is when water is solid,
steam is when water is gas, and water usually refers to
its liquid state.
Water
is a transparent, odorless, and tasteless liquid. It
illustrates the three states of matter: solid (ice), gas
(steam), and liquid (water). The form it takes depends
upon the temperature. At low temperatures, the molecules
do not move around as much and form a crystalline
structure that is rigid (ice). In the liquid state, water
molecules move more freely. Water molecules in the form
of steam are moving very fast with large spaces between
the molecules. Although ice is crystalline, it tends to
have the molecules in a rigid structure that is spaced
farther than the molecules of liquid water and this is
quite important, for if ice were denser, it would sink in
water. Imagine what would happen if icebergs grew from
the bottom of the ocean instead of floating on the
surface.
Water
is essential in animal and plant nutrition. It is used in
science and industry in making many products. Waterways
are used to transport materials and dispose of wastes.
Water is also a cooling agent, a cleansing medium, and
entertainment mechanism.
Water
most probably originated on this planet as gases were
being emitted from volcanoes. The Earth's atmosphere
captured this water and has continuously recycled it
throughout time, in what is called the water cycle. Water
evaporates and forms clouds. The clouds provide rain and
snow, which is collected in rivers, lakes, underground
reservoirs, and oceans that are the source for further
evaporation.
The
water cycle is a major driving force on our planet. Water
is in constant motion, evaporating into the atmosphere to
from oceans, lakes, rivers, and streams. When the
atmosphere can no longer support the moisture within the
clouds, we experience rain, snow, hail, or sleet. Water
is returned to the system through drainage, which results
from the melting of snow that has accumulated during the
winter months. This water flows on the surface of the
Earth and percolates through the Earth as groundwater.
Water is not actually consumed but is continuously
recycled.
Water is a chemical
combination of hydrogen and oxygen. Water is a colorless,
odorless, and
tasteless substance.
Point out hydrogen and oxygen on the periodic chart. Ask
the children if they know what hydrogen is. The element
hydrogen is a gas. Ask the students if they know what
oxygen is. The element oxygen is a gas. Water,
therefore, is a combination of two gases that form an
entirely different substance and state of matter!
Water
is very important to our everyday lives. Emphasize to
your students, because they are so familiar with water,
that they take it for granted. You may want to interject
some environmental concerns that
clean water is important for humans and most organisms to
survive.
Water
is an important commodity to all organisms that live on
Earth. Although it appears as if we will never run out of
water, only 3% of all of the Earth's water is fresh (2/3
is locked up as ice, 1/3 as groundwater, lakes, and
atmosphere), 97% is salt water which is unusable by most
land organisms' metabolic systems.
Humans
demand clean water. In some areas there are more people
than clean water. Methods to clean used water are
becoming more widespread. The end product is referred to
as “recycled water.” Instead of nature cleaning the
water, humans have created factories that accelerate
cleaning the water. They use filtration, chemical
additions, disinfection, and microorganisms to clean
water. The term “recycled water” implies that water has
been cleaned naturally or by methods developed by people
to reclaim water.
Water
can be recycled for billions of years. Once water is
formed on Earth, it has the ability to change forms
easily. If water becomes dirty or polluted when it is a
liquid, it can clean itself through evaporation process,
form a cloud, and then come back as clean rain water.
