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Physical Science of Water

Author(s): David R. Caprette, PhD

Hydrogen and Oxygen Gases

In their elemental form, both hydrogen and oxygen are gases at standard temperature and pressure. Both gases are diatomic, that is, hydrogen and oxygen are normally found as molecules, each molecule consisting of two identical atoms that share orbiting electrons. 

One property of gases is that they fill space. Gases do not stay confined, but will mix with other gases and certainly will fill any vacuum. Why? 

Understanding the properties of gases was an important pursuit of 19th century chemistry, and it helped lead to the development of modern molecular theory. In turn, we needed to understand the behavior of molecules in order to understand the reasons for the unique properties of water.