A domain made up of prokaryotes, first discovered living in extreme environments

Explanation:

Prokaryotes arose during the Precambrian Period 3.5 to 3.8 billion years ago. ... The domains Bacteria and Archaea are the ones containing prokaryotic organisms. The Archaea are prokaryotes that inhabit extreme environments, such as inside of volcanoes, while Bacteria are more common organisms, such as E. coli.

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graph slopes whilst gas cools, then it is flat whilst conensation to liquid happens, the coolong liquid then graphs as a slope when it solidifies graph is flat

latent heat

answerdmitry mendeleyev made a workable classification of the elements