Y ICE doesnt melt when placed in microwave oven?

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    Ice Microwave oven
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Discussion Overview

The discussion centers on the phenomenon of ice not melting when placed in a microwave oven, exploring the underlying reasons and mechanisms involved. Participants examine the behavior of water molecules in both solid and liquid states, as well as the implications of microwave energy absorption.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express surprise at the claim that ice does not melt in a microwave and seek explanations for this observation.
  • One participant suggests that water molecules lose their dipole characteristics when in a solid state due to hydrogen bonding.
  • Another participant explains that in the liquid state, microwave energy is converted into molecular movement, leading to heating, while in the solid state, molecular movement is restricted.
  • A participant shares a personal experiment where ice cubes melted completely after 90 seconds in a microwave, indicating that melting does occur, albeit over time.
  • One contributor discusses the resonant frequency of microwave radiation and its effect on water molecules, positing that only surface molecules of ice interact with microwaves initially.
  • Another participant draws a parallel between this discussion and the phenomenon of water not boiling in a microwave, noting that both processes involve latent heats of fusion and vaporization.
  • Concerns are raised about superheating and the potential for water to explode when disturbed after being heated in a microwave.
  • Some participants mention the high heat of fusion of water, suggesting that significant energy is required to convert ice to liquid water.
  • There is a mention of the difference between heat and temperature, with a suggestion that a temperature-entropy diagram could clarify the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the reasons behind the melting behavior of ice in microwaves, with multiple competing views and explanations presented throughout the discussion.

Contextual Notes

Participants note the complexity of the processes involved, including the latent heats of fusion and vaporization, and the time required for phase changes, which may not be fully resolved in the discussion.

sphyics
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i was dumbstruck :bugeye: after hearing the statement "that ice didn't melt when placed in microwave" from one of my friend, and its indeed true i checked by myself.And now I'm looking for the reason :)
 
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sphyics said:
i was dumbstruck :bugeye: after hearing the statement "that ice didn't melt when placed in microwave" from one of my friend, and its indeed true i checked by myself.And now I'm looking for the reason :)

I guess the water molecules are not dipoles anymore, when bound within a crystal structure, via hydrogen bonding.
 
As far as I understand ,when in the liquid state the absorbed microwave energy is converted into molecular movement of the polar water molecules this giving rise to heating.In the solid state the molecules are strongly attracted to other molecules this severely restricting their movement.The ice will melt, it just takes time.
 
I just put in 4 icecubes on a plate at full power. They were completely melted after 90 seconds.
 
sphyics said:
i was dumbstruck :bugeye: after hearing the statement "that ice didn't melt when placed in microwave" from one of my friend, and its indeed true i checked by myself.And now I'm looking for the reason :)

I do know that the microwave radiation provides a resonant frequency for transitions in rotation state of the water molecules. I assume that interaction with the microwaves whips the water molecules into spinning motion. When such a spinning water molecule collides with another molecule the rotational kinetic energy converts to other kinetic energies. That is, energy is pumped into the assembly of water molecules in the form of rotational kinetic energy of individual molecules, and subsequently that energy becomes distributed over all the possible motions of the molecules; the water heats up.

I think that when water is in ice-form there is no transition available that resonates with the microwaves. Presumably only the water molecules on the surface of the ice are free enough to interact with the microwaves. So initially ice will absorb almost as little of the microwave's energy as, say, glass does.

As more and more water transits from ice to water form there is more and more opportunity to absorb energy from the microwaves.

Cleonis
 
This question is similar to "Why water does not boil when placed in microwave oven"?
It heats anyway and with time it melts and boils.
 
sphyics said:
i was dumbstruck :bugeye: after hearing the statement "that ice didn't melt when placed in microwave" from one of my friend, and its indeed true i checked by myself.And now I'm looking for the reason :)
Water has a rather high heat of fusion. It takes quite a bit of energy (333.55 kilojoules/kilogram) to convert ice at 0°C to liquid water at 0°C. The same amount of energy applied to liquid water initially at 0°C will raise the temperature of that water to about 80°C.
 
Bob_for_short said:
This question is similar to "Why water does not boil when placed in microwave oven"?

Quite right, heating water in a microwave is all fine and dandy until you take it out and put a spoon in.

Exploding water is acutally quite a sight.
 
xxChrisxx said:
Exploding water is acutally quite a sight.

That should be a quite pure water, distillated or so.
 
  • #10
Bob_for_short said:
That should be a quite pure water, distillated or so.

And in a very smooth beaker
 
  • #11
Bob_for_short said:
This question is similar to "Why water does not boil when placed in microwave oven"?
It heats anyway and with time it melts and boils.
Yes, but the recent discussion on superheating of water misses the point to some extent. The reason water does not melt or boil (easily) is because of the latent heats of fusion and vaporization of water. It takes about the same time to raise liquid water from 0°C to 100°C as it does to change ice at -40°C to liquid water at 0°C, and it takes even longer (a lot longer) to completely boil liquid water that is already at 100°C.
 
  • #12
This is the tricky thing about people not realising the difference between heat and temperature.

a t-s diagram would help... (maybe)??
 

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