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Adding energy to water makes it's temperature increase. This continues until it reaches 100 °C (at 1 atm) when it turns to vapor with a vaporization energy of 2257 kJ/kg. But if we lower the pressure on the water, it can start boiling at lower temperatures. In this case, would it's vaporization latent heat still be 2257 kJ/kg?

If not, how does the latent heat of water depends on boiling temperature or vapor pressure?

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  • $\begingroup$ Why would you expect it to stay constant? What do you think the heat of vaporization is at the critical point? $\endgroup$ – Chet Miller Jan 17 at 0:00
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    $\begingroup$ The heat of vaporization decreases as the temperature increases, until it becomes zero at the critical temperature. $\endgroup$ – David White Jan 17 at 1:18