The presence of this gas in a sample is indicated by a change of cobalt(II) chloride from sky blue to deep purple. The "slip ratio," which depends on a factor named for the "quality" of this gas, measures the ratios between the velocity of this gas and a liquid along the course of a pipe during two-phase flow. A molecule of methane reacts with a molecule of this gas to produce carbon (*) dioxide and three hydrogen atoms in a process known as the "reforming" of this gas. This is the working gas of a machine that was invented by Thomas Newcomen, 
The presence of this gas in a sample is indicated by a change of cobalt(II) chloride from sky blue to deep purple. The "slip ratio," which depends on a factor named for the "quality" of this gas, measures the ratios between the velocity of this gas and a liquid along the course of a pipe during two-phase flow. A molecule of methane reacts with a molecule of this gas to produce carbon (*) dioxide and three hydrogen atoms in a process known as the "reforming" of this gas. This is the working gas of a machine that was invented by Thomas Newcomen, and whose ideal performance follows the Rankine cycle. For 10 points, name this gas consisting of two hydrogen atoms and one oxygen atom.
The presence of this gas in a sample is indicated by a change of cobalt(II) chloride from sky blue to deep purple.
steam [accept water vapor or other answers containing water; accept H2O before "oxygen" and prompt thereafter]