Oxygen
If an astronaut strikes a match in
space, nothing happens. On Earth the tip bursts into flame because it reacts
with a gas that is part of the air. That gas is oxygen.
WHAT IS OXYGEN?
Oxygen is invisible and has no
smell, but it makes up about a fifth of the air around us. Oxygen is an element.
Elements are basic substances that combine to form all the materials found on
Earth. Water, for example, is a combination of the elements oxygen and hydrogen.
Rust is oxygen combined with iron.
Oxygen is the most common element
on the planet. Almost half the weight of Earth’s crust is oxygen, but the oxygen
is combined with other elements in rocks.
LIFE NEEDS OXYGEN
Except for a few kinds of
bacteria, all living things need oxygen. Without it they would die. Animals that
live on land breathe oxygen from the air into their lungs. You are doing that
right now. Plants that live on land take in oxygen through tiny openings in
their leaves. Insects have tiny holes in their shells that allow oxygen to seep
in. Animals and plants that live underwater absorb oxygen that is dissolved in
water.
Oxygen gets recycled from plants
to animals and back again. Green plants combine the Sun’s energy with water and
carbon dioxide to create food for themselves. In the process, the plants produce
oxygen and release it into the air. Animals, including humans, breathe in the
oxygen. Animals breathe out carbon dioxide. Plants use the carbon dioxide to
make more oxygen.
HOW DO WE USE OXYGEN?
Anything that burns needs oxygen.
When wood burns, it is actually combining with oxygen. The flame of a candle or
a gas stove is produced by oxygen combining with other elements. Fossil fuels
such as oil, coal, and natural gas also need oxygen so that they can burn.
Burning, a process known as combustion, produces heat. We use the heat to keep
buildings warm, cook food, produce electricity, and move our cars and
trucks.
Animals use oxygen to keep their
bodies working and to move around. Their muscles need oxygen for energy.
Hospitals give oxygen to patients who are short of breath. Some pilots and
mountain climbers need to breathe oxygen from special tanks in order to travel
at high altitudes where the air is too thin to breathe. Divers need tanks
containing oxygen so that they can spend time exploring underwater.
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The Environment
