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Joined 1 year ago
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Cake day: June 22nd, 2023

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  • Do it! it is easy to do at home! Just wear some gloves and safety glasses, those jars can easily shatter during the heating process if you use too hot of a heat source. I recommend a glass top electric stove, or put some kind of metal plate between your jar and the burner to help spread out the heat. Once you seal the jar, take it off the heat right away, so it doesn’t build pressure. I boiled mine for a few minutes before sealing to try and get some of the devolved gasses out, and lightly set the lid on top to help the steam push out all the air.






  • sixfold@lemmy.sdf.orgOPtoScience@beehaw.orgBoiling water with Ice
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    1 year ago

    Exactly. it was bottled at atmospheric pressure while it was boiling, so 1 atm and 100 degrees C. Check this graph to see the relationship between the water’s temperature and it’s pressure in the jar (since there is no air, only water vapor). If the vapor is condensed, then the pressure drops below the curve on the graph, that is, the pressure in the jar is lowered below the vapor pressure of the water. Any time the pressure is below the vapor pressure, the water will boil, releasing vapor, until the pressure is equal to the vapor pressure. The pressure does not become negative, it is still positive, just lower than the vapor pressure at the given temperature. You can get below the vapor pressure curve by changing the temperature too, which is what we usually do when boiling water at a pressure near 1 atm (760mmHg)

    http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/watvap.html#c2

    (1 atmosphere is ~760mmHg)

    a slight aside, there is an important difference between the total pressure of the air, and the partial pressure of water vapor in the air. Inside the jar, the two are equal, but in a dry location (not humid) the partial pressure of water vapor is usually less than the vapor pressure of water at that temperature, but since the total large pressure of the atmosphere would not allow a pocket/bubble of very low pressure water vapor to form inside the bulk water, the water cannot boil, but it will evaporate at the surface anyway until the partial pressure of water is equal to the vapor pressure (very humid).













  • It’s very difficult and dangerous to be near an MRI ‘shutting down’. Assuming what you mean is turning of the magnet. The magnet is always on, its a coil of superconducting wire submerged in liquid helium with a very large permanent current flowing around it. In order to turn off the magnet quickly, the electric current must be quenched, which can happen if the coil every stops being a super conductor. The current starts heating the coil, causing the liquid helium to boil off, which doesn’t cool the coils as efficiently, and causes a rapid run-away effect where huge volumes of helium explode out of the machine, displacing all the breathable air in the room and blasting all the doors off their hinges, maybe even breaking windows. There’s a lot of energy stored in the coil. It’s not easy to turn it off.

    Look up videos of MRI quenching