Two questions. 1. An ice cube is submerged in a glass of water. 2. An ice cube is floating in a glass of water. When the ice melts, does the water level rise, fall or stay the same in either case?

in the first case.. The ice cube is less dense than water. As it melts the water volume occupied is less. The water level will fall a small amount.

the second case
the level will stay the same.
The mass of the ice cube = mass of the water displaced. The volume and density difference is the small amount of ice above the surface.. Once melted the mass of the system stays the same. the ice gains density and looses volume to equal the volume of the water it displaces.
(if you look really close the system will shrink (water level reducing) just a tad when going from 0 to 4 C..
and then start to expand again. )
Hope this helps

Liquid water is most dense, at 4 °C and becomes less dense as the water molecules begin to form ice as the temperature drops to 0 °C. This is due to hydrogen bonds forming between the water molecules, which line up molecules less efficiently when water is frozen. The result of this is that ice floats on liquid water.
2)yes there will be rise in level of water when ice melts when ice melts, it absorbs as much heat energy.
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Richa

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This message has been edited. Last edited by: DorianGreyed,

What little science I had in middle school, high school, and college tells me that Peteeo is correct. I've read similar questions is various books and all over the net, and the answer is always the same: The water level stays the same.

DG: You are not agreeing with Peteeo, who wrote two different effects.

I was referring to the second question, which is the most asked. Sorry for not being clear. In regard to the first question, I think it depends on whether the ice is introduced to the water, or was already floating in it. It is also unclear at which point the water level is first measured. If the ice is introduced, then the water level will rise. If the ice was already floating, then I honestly don't know, but, having read most of Peteeo's answers in the Science and Math forums, I have to think that he is probably right.