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up vote 9 down vote favorite

If I have an ice cube of, let's say, for example (15$\times$15$\times$15 cm), it was put inside a container of internal dimensions (15$\times$15$\times$15 cm), and the container is strong so as not to allow compression, will the cube melt when put at room temperature? Or will it just melt partially? What will happen exactly?

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1  
what is the material of the container? What is the mass of the container? What is the initial temperature of the container and the ice cube? If you want to know exactly, you must be precise and complete in your setup. – Bill N 20 hours ago
3  
Were you possibly asking this question, forgetting that water shrinks when it melts, unlike most other substances which expand? Reading this makes me expect to see an identical question, but specifically asking about a substance which expands, which I now wonder what will happen since there is no room for it to expand. – Ryan 15 hours ago
up vote 31 down vote accepted

Sure it can melt. Ice is less dense than liquid water. The difference in volume (the molten water will not fill the cube completely) is filled with water vapor.

In case you are wondering why water vapor is created:

You might have seen the experiment where water starts to boil if you put it in vacuum. If there is no vacuum pump to remove the vapor, the boiling will stop once the vapor has sufficiently increased the pressure. (The equilibrium pressure is called the vapor pressure, and depends on temperature.)

The same thing happens in your example: if the melting ice were to create a vacuum, the water would boil until the vapor had filled it.

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Why do you think density has anything to do with melting? – Bill N 20 hours ago
6  
Imagine the opposite: a cube filled with water at freezing temperatures. If the structure is rigid enough, the water will not freeze, as the melting point at high pressure is too low. The pressure increases precisely because of the volume change during melting. – polwel 20 hours ago
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I think in this case the water will freeze, but will create a different kind of ice ( with different crystalline structure) ex. Ice ii, Ice iii, Ice iv it all depends whether the container can handle the pressure – KareemNabil 20 hours ago
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Uh, good point. Did not remember that ice has some solid phases 'above' liquid in the pT diagram. Anyway, none of this is relevant to the question :) – polwel 20 hours ago
    
another question if you don't mind. why will it be filled with water vapor, why not vacuum ? – KareemNabil 20 hours ago
up vote 2 down vote

All bodies come into thermodynamic equilibrium, and so will the cube with the ice inside, by black body radiation from the environment and convection on the box, so it will melt if the environment temperature is higher than 4C . A relevant answer is here

the height the water has increased due to the melted ice is exactly the same as the height increase due to buoyancy before the ice had melted.

If the outside temperature is below 0C the ice will not melt but cool further, the equilibrium will be a lower temperature

When water transitions from a liquid to a solid (freezes), its density decreases by about 9%, which is unusual among chemical compounds. This is the reason why ice floats in liquid water. When water is in the ice state, it's density starts to increase slightly as the temperature falls further below zero, though it never becomes as dense as liquid water.

So there will be no problem . If you filled the box with water and froze it, there would be great pressure on the containing box due to the 9% decrease in density as the crystals of ice form. The reason for burst pipes in a freeze.

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up vote 2 down vote

Cannot stop heat transfer. The cube will come to the temperature of the room.

If the room is 68°F then the pressure will be 0.0231 atmosphere. The vapor pressure of water at 68°F.

The vapor will be approximately 9%.

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protected by Qmechanic♦ 14 hours ago

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