Oxygen

November 24, 2012 3:06 am

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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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