If I filled a box TO THE BRIM with 75% water and 25% ice, sealed the box shut in a way that it was as if it was never openable, and then waited for the ice to melt, what would happen? Would it manage to destroy the box? Would I accidentally start a black hole that would suck up the Earth and kill us all?
In: Physics
If you put the indestructible, incompressible box in a special make-believe place, where no heat can warm it from the outside, and the pressure outside the box is exactly the same as inside the box:
The temperature of the water would decrease.
The temperature of the ice would increase.
Some water molecules would freeze when they got to 0°C and some ice molecules would melt when they got to 0°C.
When you measure temperature, you measure the average of all molecules. The final temperature inside the box will settle somewhere in the middle between what the ice started at and what the water started at.
If more ice melts than water freezes (likely):
Ice takes up more space than water, which means when it melts, there is now less pressure inside the box.
Like if you heat up a glass and press the mouth to your skin. The negative pressure — created as the air inside cools — pulls your skin inside until the forces are equal (“equilibrium”).
The water is also cooling down, which also reduces the pressure (cold liquids shrink aka get more dense).
So the box’s sides are being pulled inward with a strength that depends on the starting conditions. But the box is indestructible and incompressible, so it’s fine.
If you opened the box, it would make a sound like opening a sealed jar.
If more water freezes than ice melts (unlikely):
For the opposite reasons as above, there is now more pressure inside the box.
So the box’s sides are being pushed outward with a strength that depends on the starting conditions. But the box is indestructible and incompressible, so it’s fine.
If you opened the box, it would make a sound like opening a soda container.
If you put the indestructible, incompressible box on Earth at room temperature, where heat can warm it from the outside:
You get a black hole. Everyone dies.
Just kidding. Eventually the inside of the box and the outside of the box will be the same temperature.
The water that used to be ice shrunk (remember, ice = bigger than water).
The water that used to be…colder water…grew (remember, hot liquids expand aka get less dense).
But we started with more water, so we grew more than we shrunk (also, the water…that used to be cold water…that used to be ice…also grew).
So same as scenario #2. And the box is still fine.
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