What is the least dense liquid under normal conditions, room temperature, one atmosphere of pressure, doesn't combust upon contact with air, also wouldn't kill a human just for being in the same room as it?


Isopentane $\ce{C5H12}$ has the density of $0.6201~\mathrm{g\,cm^{-3}}$ at $20~\mathrm{^\circ C}$ [1, p. 3-330].


  1. Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; CRC Press, 2017; Vol. 97. ISBN 978-1-4987-5429-3.
  • $\begingroup$ That is... surprisingly dense. Water is known to be 'heavy' in common speech, but there aren't really any liquids which are a lot lighter apparently. $\endgroup$ – orlp Apr 25 at 8:11
  • 2
    $\begingroup$ @orlp That's due to the constraint imposed by OP: the compound must be liquid at NTP conditions. Once the constraint removed, there are more interesting things such as solution of lithium metal in liquid ammonia or good old liquid hydrogen with the density of $0.0709~\mathrm{g\,cm^{-3}}$, but that's not what the question is about. $\endgroup$ – andselisk Apr 25 at 8:16

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