Howdy all,
Hope this is the right flair.
Yesterday I discovered one of our glass Tupperware containers in the hatch of my wife’s car and the lid is sucked in on itself.
The lid has four clips that snap under the lip of the glass and it’s air tight I would assume. It has remnants of her buffalo chicken chili in it. That has dairy in it.
It’s also been relatively warm here until yesterday when I discovered it. It was 15 degrees F difference.
Thanks in advance for your answers.
In: Biology
Take a more extreme example, you have sealed it in Denver and flew to NYC. You get off the plane and try to open the container and it is hard as hell to get open. What happened? Simple, you sealed it at an atmospheric pressure of 1 atmosphere minus 1600 meters (so about .82 atmospheres) and then you tried to unseal it at 1 atmosphere. All of that air is trying to get in to equalize, since the pressure in the container is less than the outside. Now is a good time to explain a fundamental law about pressures, high pressure always tries to root out low pressure. It is why your ears pop as you go up in altitude, the air inside the ear is higher pressure and it is desperate to get to that low pressure air.
So, if you put warm food in the container and seal it, the air cools and densifies, meaning it takes up less total volume. The pressure inside the container is slightly less than outside, and the outside air really really wants to get into the container. That vacuum you feel is actually the pressure of the outside air trying to get *into* the container, which is being prevented from getting in by the airtight lid.
You can repeatedly and quickly demonstrate this with a jar candle. Light a candle and place the lid on the top lightly. As the oxygen is consumed by the flame you will see (and hear) the lid suck closed as the air pressure is reduced because the oxygen is being taken out of the air and deposited as ash.
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