What is oxygen?
It has no taste, color or smell, but we could not survive without it! It's oxygen, a gas needed by living things. Humans and animals take in oxygen from the air as they breathe, then exhale (breathe out) carbon dioxide, which plants need in order to survive.
As plants use carbon dioxide to make their food, they release oxygen back into the atmosphere, where humans and animals breathe it in once again.
Oxygen is an element, or a substance that cannot be broken down into other substances. However, oxygen can be combined with other elements to form new substances. For example, when oxygen and hydrogen combine, they form the compound water!
Oxygen is all around us! It makes up 21% of our air. Furthermore, most of the mass (or "stuff") in water and in the human body is oxygen, as is half of the mass of our Earth's crust! As you can see, Earth as we know it would not exist without oxygen!
(by Mya Kagan)
Exploration
Take a deep breath! Can you feel your lungs fill with oxygen? When you breathe out, can you feel the oxygen leaving your body if you hold your hand a few inches from your mouth? You may be able to feel oxygen, but can you see it? No!Water, on the other hand, can be seen! It's hard to believe that the liquid water is made of two gases""oxygen and hydrogen! How is the liquid water different from the gas oxygen? Can you see it? Yes, unlike oxygen, you CAN see water! Furthermore, gases don't like to be trapped in containers""they flow all around us. If you pour a liquid into a glass, will it quickly try to escape? No! Now think of ways that the gas oxygen and the liquid water are alike? We know that oxygen doesn't have a taste. Does water have a taste? Oxygen is colorless. Does the water in your glass have a color? No!