4 ms·

What exactly is the distinction between water vapor and steam?

• wnoise 3y ago
  Temperature
• px43 3y ago
  Where I'm sitting now, the humidity in the air is about 40%. Would you consider that to be "steam"? I feel like steam generally needs to be hot, or at least somewhat warm. Cold steam exists, but is specifically called out as an exception to the rule. Maybe steam needs to be somewhat translucent?
  • mikewarot 3y ago
    Humidity is a percentage of the amount of water that could be in the air, which is when the vapor pressure of water is equal to the partial pressure.[1] So if you're in a room 20 °C, the partial pressure of water is 0.0231 Atmospheres * 40% --> 0.00924 water (0.924%) Steam is 100% water, and generally can only happen at 100 °C or higher. The highest humidity/temperature I've experienced is about 100% at 99F, which works out to around 7% water in the air. It was a miserable day, and I was a young/healthy kid at the time. [1] https://en.wikipedia.org/wiki/Vapour_pressure_of_water https://en.wikipedia.org/wiki/Vapour_pressure_of_water
• Sai_ 3y ago
  Isn’t steam just water vapour off boiling water? I.e., water vapour which, on condensing, yields heat to the surface on which it condenses. Steam is hot water vapour, IOW.
• pard68 3y ago
  steam is specifically from heating water and often enough is a gaseous water. Water vapor (or "wet steam") is an aerosol of liquid water. But both are means of evaporation.