How to melt ice?

  • Thread starter HK911
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  • #26
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hmm

If you have windows and its a sunny day you could use a magnifying glass. Otherwise - wrap the cube in a black cloth and sit on it.
 
  • #27
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place some high resistance electric coils near by the ice to melt it fast
 
  • #28
Water (H2O) is unusual in that the solid phase is less dense than the liquid phase, hence ice floats on water - a rare physical property which actually is essential for life as we know it*.

This relates to the fact that under typical surface conditions (i.e. what might be considered normal pressures and temperatures at the surface of a planet) H2O has a negative Clapeyron slope - that basically means that the melting temperature goes down as the pressure is increased. Consider this: imagine you had a body of water all at the same temperature, from experience we know that the ice will form at the surface of the water (I guess we have to be careful here - maybe that happens because the air above the surface is colder, but I believe in laboratories we can control the conditions and can convince ourselves that it is not because of the colder air at the surface); now where is the pressure the greatest? Of course, the pressure is greatest at the bottom of the water because it has a load of water on top of it, but the ice doesn't form at the bottom - the ice forms at the top where the pressure is lowest. So does this not mean that water has a higher freezing point at lower pressures?

That's my understanding anyway.




*If ice was denser than water then the oceans would have completely frozen, because there wouldn't have been an insulating cap of ice at the top to stop all the water from getting very cold (and then freezing solid), life needs liquid water, ergo, if the oceans were frozen we wouldn't have life.
Yeah I know that but it doesn't prove that reducing and heating would be better than increasing pressure at all.

Bodies of water would also freeze from the bottom up making life difficult to get started in the first place.
 
  • #29
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Q: Can solvents be added to the ice?
A: No, nothing can be added to change the chemical composition of the ice or that creates an endothermic or exothermic reaction. Clarification: in any part of the device, no substance that creates an endothermic or exothermic reaction is considered to be passive as it is stored chemical energy. Solvents include but are not limited to fertilizer, cat litter, sand, bleach, sugar.
Q: Restricted
A: Any passive field may be used (i.e. gravity)
Q: Can we use additional water?
A: As long as it does not come in contact with the ice, ice/water mix. However, if you’d like, you may use the water from the melt.
Q: Can the ice be broken up?
A: Not prior to the testing time, and only by some passive means during the testing time…good luck with that!
Q: How about deformable materials such as sponges
A: Sure.
Q: Can the ice be dropped
A: No
Q: Can we use hot water
A: The device must start at room temperature, which includes any additional water.
Q: Restricted
A: No, a generator can not be used.
Q: Can we focus the light with lens
A: Yes, Lens can be used.
Q: How about dry ice?
A: No dry ice
Q: Can we add pressure to the ice?
A: Yes, passively. For example, a weight may be placed (not dropped) on the ice.
Q: Could you post your PowerPoint slides from lecture?
A: No, but I did post a summary of the analytical model that has more details then what I went over in class.
Q: Do we have to provide a catch basin for water run off?
A: There is no requirement for a catch basin.
Q: Exactly how big is this block of ice?
A: A 10 oz coffee cup, ¾ filled with water. This is approximately 200 mL of water.
 
  • #30
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Above is a few of the frequently asked questions. If we used the plates, would it be best to place it in some sort of container? We were thinking of designing a box made from acrylic with holes in the bottom and top to all air to flow. Should be do that are just let it sit in the air with no casing around it?
 
  • #31
Gravity considered passive, eh? Because if you held the ice in callipers as it melted it would pitch to the floor, no one is dropping it, the higher up you put it the better, it would melt in no time then. :) as it would be spread over a massive surface area. Sadly I think that counts as dropped though. If you used a catalyst that increased ice melting without chemical reactions that might be passive?
 
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  • #32
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Gravity is passive. But how high would you have to place the ice cube to actually have some sort of effect. The experiment would be carried out on a table. Here is some more information.

Project Statement:
The project team is to design, analyze, build and test a "passive" heat transfer device to enhance the defrost process as realized by the melting of ice. Passive means no energy input is to be utilized during the operation of the device. To remain in context with the above described devices, the ice may not be modified in any manner. The device must also begin at room temperature. A device must be manufactured by the project team. At the end of the semester a competition will be held during which the device will be judged on the basis of the ice melting rate produced, the mass of the device, and its cost. The device must fit inside a box of dimension 14" x 14" x 12"
 
  • #33
LURCH
Science Advisor
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Above is a few of the frequently asked questions. If we used the plates, would it be best to place it in some sort of container? We were thinking of designing a box made from acrylic with holes in the bottom and top to all air to flow. Should be do that are just let it sit in the air with no casing around it?
Open to the air would work best, I should think. I did not realize it was such a small block of ice. The inside of a metal ice cube tray would not work very well on this particular body of ice, you would only and a cutting it into two or three pieces. You will want your plates to be much closer together than this. Also, you should try to get them to line up with each other (if you use the "sandwich method" of placing one grate beneath the block and one above it).
 
  • #34
Adding pressure will indeed melt more ice for reasons explained by "billiards". A quick test is that you can press your thumb into a block of ice and create a small dimple in the ice surface.

Anyhow, I would consider making a device where ice is placed inside a spring loaded "vice". At the start, the spring would be compressed most and will exert the maximum force on the ice.

As the ice melts, the spring would cause the vice jaws to move closer but still maintain contact with the ice.

Also, I would allow the water produced to run off. Keeping the ice in water-bath will set up an equilibrium between the ice-water system and some of the water molecules may become ice again. Also, one would expend part of the energy to evaporate water.

You may also think about rigidly attaching some sort of fins for accelerating the heat transfer. Make sure that the fins are integral (read: welded) to the vice jaws. Or else, the fins would be useless if there is an air gap between them and the jaws.

I am sure you can come up with multiple designs. This is just one possible solution. However, if you wanna put some mathematics to all of this, it is beyond me. Look into FEA if you want to decide between a couple of designs.

Good luck!

Another option is to concentrate the force on a small area to create more surfaces really rapidly.
 
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  • #35
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Yeah I know that but it doesn't prove that reducing and heating would be better than increasing pressure at all.
Uh, ok, you're right, but I don't remember claiming to prove anything, or even hinting that "reducing and heating would (not) be better than increasing pressure" ... whatever :rolleyes:.

Bodies of water would also freeze from the bottom up making life difficult to get started in the first place.
No they wouldn't, even if the ice formed in the deep it would float up to the surface by buoyancy. You can't be still be claiming that the melting temp of ice is higher at higher pressures, I would agree if we were talking about ice III, V, or VII, but we're talking about everyday "normal" ice here: ice I, which if you look at the http://www.homepages.ucl.ac.uk/~ucfbanf/water_ice.htm" [Broken] for water ice you will see has a negative Clapeyron slope. As I mentioned earlier this is important for life, because it means that under great ice bodies, where the pressure is high, the ice can melt more easily providing underwater reservoirs which may harbour life (chemoautotrophic life, probably) - c.f. Europa. It's also an important mechanism for the movement of glaciers, the water at the bottom of a glacier pushes the ice upwards reducing friction with the ground accomodating "basal sliding".
 
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  • #36
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Q: Can solvents be added to the ice?
A: No, nothing can be added to change the chemical composition of the ice or that creates an endothermic or exothermic reaction. Clarification: in any part of the device, no substance that creates an endothermic or exothermic reaction is considered to be passive as it is stored chemical energy. Solvents include but are not limited to fertilizer, cat litter, sand, bleach, sugar.
....
Q: Can we use additional water?
A: As long as it does not come in contact with the ice, ice/water mix. However, if you’d like, you may use the water from the melt.
Hmm... If you can only use additional water if it doesn't come in contact with the ice, can you use other chemicals if they don't come in contact with the ice?
 
  • #37
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12x12x14 isn't a very big box, and a foot of gravatic drop will add very little energy to a block of ice. Even one the size of a large Tim Horton's coffee. So...Hmmm...

Chemicals...out
Gravity...... in, but not usefull
Smashing....in, but not usefull (will the ice break in a 9" drop? I think not.)
Melt water..in
New water..in, so long as it does not mix with melt.
Lenses.......in.

Question: If I put the ice in a beaker, and I put the beaker in a box, can I pour boiling water into the box to heat the beaker, and by conduction the ice? Unknown, but bet no. Please clarify OP, 'cause that would be the best bet hands down.

Otherwise...

A Box Oven!! Used to cook food in some areas of the world, but a 2 min. time limit means some serious mods...lol.

How about an insulated box say formed with poly or foam insulation in a box shape insulating an enclosed parabolic mirror (say aluminum foil for instance) focused on the bottom of the block. Make the lid a big lens focused on the top.

Basically trying to trap as much passive energy as possible inside the box with insulation, and focusing the energy as effectively as possible to create melt. (guessing the measure of melt decides the winner.)
 
  • #38
Sodium or Phosphorus?

How about placing ice in a container with a false bottom and keeping either Sodium or Potassium in the bottom chamber?

Just add water!!!
 
  • #39
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Wysard, boiling water can't be used. Any additional water used must be at room temp.
 
  • #40
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Also, the lense was one of our ideas but the problem is the experiment is conducted indoors under fluorescent light. So do you think the light would give enough energy.

Another very simple idea was to place the ice in a zip lock bag and drop the bag into a beaker with water at room temperature. Any suggestions?
 
  • #41
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How about placing ice in a container with a false bottom and keeping either Sodium or Potassium in the bottom chamber?

Just add water!!!

No chemicals can be used at all.
 
  • #42
You may just choose to keep the zip-loc bag under an open faucet. That does not violate any of the conditions.

Ok, you have got so many people hooked to this thread. Time to take stock of the situation. Think about what all you have at your disposal. So far you have the following you can use (with heat transfer mechanisms):

1. Light (radiation)
2. Pressure (thermodynamics)
3. Fluids (convection and conduction)
4. Air (convection and conduction)
5. Friction (energy conversion, increase in surface area)

Now, the task for you is to pick and combine them in the best possible manner.
 

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