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At standard pressure, helium never freezes, so that's clearly the coldest liquid—but it's also a monatomic substance.

Diatomic hydrogen freezes at 13 K.

Neon freezes at 24 K.

And then the next coldest liquid I can find documented is $\ce{OF2},$ which is liquid between 49 K and 128 K (which I only know because Robert Forward references it in the science fiction novel Camelot 30K).

Are there any other known compounds which have freezing/melting points between 0 K and 50 K?

Logan R. Kearsley
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    What non-monoatomic gases do you know? Hint: you are looking for nonpolar, small, and light molecules. I can think of just four in all that make sense to take into account. – Karl Apr 26 '22 at 19:19
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    I don't like the wording of the question. It sounds like HNQ bait. Also liquids can be supercooled well below melting point. – Mithoron Apr 26 '22 at 19:49
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    @Karl Well, O2, N2, CO2, CH4, CF4, and CCl4 all freeze at higher temperatures. OCl2 freezes at a higher temperature and is not non-polar. The analogous nitrogen compounds are all polar, and freeze at higher temperatures. What are you thinking of? – Logan R. Kearsley Apr 27 '22 at 01:07
  • @Mithoron How would you improve it? – Logan R. Kearsley Apr 27 '22 at 01:08
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    Lowest freezing point room temperature liquid? – andselisk Apr 27 '22 at 16:21
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    @andselisk That's a very different question, for which I would expect little or no overlap in answers. Neither hydrogen, nor neon, nor OF2 are liquid at room temperature, for example. – Logan R. Kearsley Apr 27 '22 at 17:52
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    The title and the text ask two very different questions. One is about a substance in the known set of substances, and the other is absolute. – Zhe Apr 27 '22 at 20:31
  • @Zhe The title was edited without my consent in a way that contradicts the body. Having not received any suggestions on how to improve it, I guess I'll take a while guess and edit it again... – Logan R. Kearsley Apr 27 '22 at 21:09

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