I always learned that water has the highest specific heat, but I recently saw that Hydrogen has a specific heat as high as 14 cal/gC and helium has a specific heat of 5 cal/gC, which would be much higher than water? Is this true? and how can it be if there are so many "proofs" in nature , showing that water has the highest specific heat?

  • $\begingroup$ related: chemistry.stackexchange.com/q/26651/23561 $\endgroup$ – A.K. Oct 30 '18 at 1:13
  • $\begingroup$ Thanks - I looked there but it does not answer my question. $\endgroup$ – suse Oct 30 '18 at 1:21
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    $\begingroup$ Yes, that's true, except that the figures are in Joules, not calories. Still, they are a good deal bigger than that for water. There is nothing strange or anomalous about it. $\endgroup$ – Ivan Neretin Oct 30 '18 at 6:01
  • $\begingroup$ You would be better to compare heat capacity in joules/mole/K rather than mass, in that case hydrogen is approx 28 , water approx 75, but for example benzene 117 and anthracene 211. $\endgroup$ – porphyrin Oct 30 '18 at 10:00

This may not be the absolute highest, but on a mass basis hydrogen gas has more than three times the specific heat as water under normal laboratory conditions. Diatomic gases under ambient conditions generally have a molar specific heat of about $7\text {cal/(mol K)}$, and one mole of hydrogen has only $2\text {g}$ mass. Thus $3.5\text {cal/(g K)}$ for hydrogen versus $1\text {cal/(g K)}$ for water.

Helium, contrary to the question, is $5\text {cal/(mol K)}$, not $7\text {cal/(g K)}$.


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