Chemical Engineering in Daily Life – Question 63: It rains and salt causes moisture to accumulate, yet bed sheets can still be dried. Why?
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This post was last edited by yjqin1 on 2015-9-4 21:08. It has been raining non-stop in Tianjin these days, so the bed sheets, blankets, and pillowcases haven’t been washed yet. But my wife and child are coming today, so I had to wash all of this in two tubs early in the morning and hang it out to dry. I just went home to get something. At a quick glance, the hygrometer reads around 88%, and the temperature is about 24 degrees (the windows are open, so wind is flowing through the room) ； A quick touch showed that the washed sheets and pillowcases were almost dry. I also noticed that the salt sculpture I brought back from Qinghai was a bit wet. Try to explain the above phenomenon.
Salt sculptures absorb moisture; at this temperature, the blanket loses water due to wind, but it isn’t completely dry – it’s only relatively dry compared to the skin
If you don’t believe it, just blow on the electric blanket and you’ll see
Wet sheets are much larger than water molecules in the air, so it feels dry after the water vapor has evaporated.
One reason is chemical: the deliquescence of salts. The salt sculptures created by teachers are surely made from natural salts from salt lakes, not refined sodium chloride; as a result, the calcium and magnesium salts contained in these sculptures tend to deliquesc, making them appear wet. Another reason is physical: the vaporization of water. Whether vaporization occurs spontaneously seems to have nothing to do with temperature or humidity, but may be related to the vapor pressure of the surface atmosphere. With good ventilation, saturation will not occur, so wouldn’t vaporization then take place spontaneously?