|MadSci Network: Chemistry|
Good question! To begin to answer that question, we should talk about what the difference between a gas and a liquid (and a solid, for that matter) really is. In fact, many substances (such as water) can exist as a solid, a liquid, OR a gas. For instance, when it's REALLY cold outside, the pond that you may swim in during the summer turns as hard as a rock! Does this mean that the water went away? NO. All that happened is the little tiny bits of water (called molecules) slowed down a LOT (because they got cold) and eventually stuck together! The opposite of this happens when someone puts some (liquid) water on the stove to boil for tea. When the water gets hot enough, you can see steam coming out, and the water really starts to bubble. That is because the water molecules have gotten so hot that they are literally bouncing off of each other, and escaping in the form of a gas! So you see, ice, "water", and steam are ALL water, just really hot, really cold, or just right! Also, oxygen and hydrogen are both gases at temperatures that YOU would find comfortable (usually called room temperature). However, if you got EITHER of them cold enough, they would eventually CONDENSE to form a liquid! So you see, a lot of things can exist as either a liquid or a gas. Water can be a gas if you heat it up to a boil, and oxygen can be a liquid when you REALLY cool it down (to more than 300 degrees Farenheit below freezing)! It just depends on how you look at it! Good Luck, Dr. Scott Miller Air Force Research Laboratory
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