Ice: Newsletter Challenge (05/30/06)

This can be done with a string saturated with salt, if memory serves.

I know you cThis can be done with a string saturated with salt, if memory serves.

I know you can lift a cube with a salty string, but I seem to remember cutting a cube slowly with string coated with salt as well.

The salted string is placed over the cube and weights are added to each end. The string will slowly cut its way through the cube and refreeze behind the string's path.

A hot wire will work as well. Nichrome wire attached to a current source will warm the wire and let you slice the ice cube. Again, the ice will refreeze after the wire passes through the cube.

You can bond two cubes of ice by adding a little water to one side and sticking them together. Sprinkling salt on one cube's side and sticking the two cubes together works as well. Of course you could also drill a hole in each cube and bolt them together. However, most people simply prefer to drop them into a glass of their favorite beverage and save the salt for a Margareta. an lift a cube with a salty string, but I seem to remember cutting a cube slowly with string coated with salt as well.

The salted string is placed over the cube and weights are added to each end. The string will slowly cut its way through the cube and refreeze behind the string's path.

A hot wire will work as well. Nicrome wire

Something appears wrong with my last post. It should read:

This can be done with a string saturated with salt, if memory serves.

I know you can lift a cube with a salty string, but I seem to remember cutting a cube slowly with string coated with salt as well.

The salted string is placed over the cube and weights are added to each end. The string will slowly cut its way through the cube and refreeze behind the string's path.

A hot wire will work as well. Nichrome wire attached to a current source will warm the wire and let you slice the ice cube. Again, the ice will refreeze after the wire passes through the cube.

You can bond two cubes of ice by adding a little water to one side and sticking them together. Sprinkling salt on one cube's side and sticking the two cubes together works as well. Of course you could also drill a hole in each cube and bolt them together. However, most people simply prefer to drop them into a glass of their favorite beverage and save the salt for a Margareta.

If salt is not available, (or has been used up in said Margeritas) one can simply use the wire with weights. The pressure will cause the wire to slice through the block in any event. Also to stick it together, simply press the two blocks together. It will re-bond into one pc.

I assume the salted string is the answer you wanted, Mr. S. Dog.

And now the why... In melting the ice, the salted string draws heat from the ice nearby, making it colder so, as the warmest water runs off with the salt it is replaced by relatively non-salty just-melted water sitting on colder-than-before ice which freezes the water.

The wires might work as well, BUT without some pressure pushing the block back together, there will just be two blocks.

(Pressure causes the ice to heat up and melt, making some water and leaving the rest of the ice a little colder. That's why skates work, but not at -40 unless you're really heavy.)

Saturate a string with salt? Don't you mean, marinate the string in brine?

The wire does not need to be salty or hot. A wire with weights on each end will generate enough pressure to melt the ice immediately beneath it. As the ice melts, the wire moves slowly through the ice, which refreezes on top of it. If weights are not available, you could use two wires and and lay the ice on top them, cutting the ice into three blocks. This is also how ice skates work. In reality the skater is moving on a layer of water between the skate and the rest of the ice.

"Cutting" through a block of ice by laying a wire weighted at the ends across its midline--it "cuts" because the wire concentrates pressure along its length, thus lowering the underlying ice's freezing point--and waiting for the wire to "melt" a "cut" path through the block is a well known junior-high/middle-school science class trick. If you held your friend in any regard you would probably have hesitated to possibly give insult with the suggestion, implicit in your bet, that he or she was not aware of the trick--or aware, that as the wire melts its way downward through the block, the melted water in the wire's path, being no longer under pressure from the wire, refreezes and refuses the block as the wire travels downward; and that by the time the wire reaches the bottom of the block, the "severing" block (the always severing but never severed block) will have fused back into a single block--that if the block can only be potentially, but not actually, cut in half--that "cutting" it will not render it, at once, in two pieces. Then, after you had demonstrated your trick, you could go on the enlighten your friend as to how the trick demonstrates a practical event encountered in everyday life: namely, the transforming of snow on the roadway into ice on the roadway--eventually, an ice pack under the snow pack--by the passage of vehicle tires over the snow.

You should not be so condesending. The question is to cut the block in half and then put it back together. The string or wire trick does not do this. It in fact passes the string through the ice with out breaking it. On the other hand in the time taken for the wire / string to cut through some of the ice will melt and thus is a second reason why you CAN NOT put the two halves back together!!!!

Yep, kinda makes you wonder about rocket scientists . . . Speaking of wondering, I wonder whether the ice would refreeze back to one solid chunk if the wire were, say, 1/2" in diameter??? Hmmmmm . . .

The block of ice WOULD refreeze into a single chunk after a 1/2" diameter wire passed through it, IF the block of ice was large enough - say a cubic yard or so.

Send us a video . . .

To Anonymous et al: Thank you for the reproof; however, I intended, perhaps too clumsily, for my "solution" to be taken in good humor--with a bit of sardonic wit, if you will. Perhaps we can simply agree that something of that intention must have been...lost in transmission...and be on friendlier terms again? I would like to add (with all due respect), that the experiment is independent of the ambient temperature in which it is performed--the trick works whether or not it's tried in above- or below-freezing conditions--your implicit conclusion to the contrary notwithstanding.

Certainly agree with that.Remember my school days, some 50 years ago doing that experiment..... and it does work. Keep the salt for the fish and chips.

A strong fine wire with heavy weights on each end is placed across the block. The heavy weight on the thin wire puts pressure on the ice and lowers its melting point. Once the water is past the wire the pressure is gone and it refreezes. The wire will slowly cut throgh the ice block and leave it whole. The same effect happens under an ice skater's blade. They are gliding on a thin film of liquid water produced by the pressure of the blade. It refreezes afterwards.

Realistically, you guys missed the boat. How many people come to a picnic with a roll of wire in their pocket, or string for that matter? Salt, sure, since it might have been brought as a condiment. Anyway, implied in the challenge is that the blocks must be separated and then reunited, not simply passing a wire or string through them.

What else are you likely to find at a picnic? Well, even though plastic wrap has made great strides, people still like to use aluminum foil as covers for portable foods. Also, you are likely to find several disposable aluminum pie plates available.

Although the size of the block was not specified, we can assume that we can obtain or fabricate a sheet of aluminum (from the pie plate or by folding over the foil until there are enough layers for adequate stiffness) which will be long enough to overhang the block of ice.

Unlike the wire example, where melting was done primarily by pressure, or salty string, where the salt solution lowers the melting/freezing point, this procedure depends on several processes, including pressure, friction, material transfer, and thermal conduction.

Heat from your hands as well as surrounding air is conducted through the foil, which is then warm enough to melt into the ice. However, gravity alone is not enough, or the lightweight aluminum would like reach a point of thermal equilibrium. A gentle sawing motion would do several things, increase friction and pressure, both generating heat. Also, carry off the resulting cold water, which would otherwise continue to absorb heat rather than the ice. "Sawing" would also continuously expose the aluminum to air, then ice, then air, etc., allowing a heat exchange from air to ice.

Another part of this technique would be to fold the "cutting edge" of the aluminum several times to strengthen it, provide larger cross-sectional area for thermal conduction, and provide a larger surface area, making a substantial kerf (thickness of the cut) which would reduce contact between the aluminum and the surfaces of the block that have already been cut.

Once the block was cut in half, a sun-warmed sheet of aluminum would be inserted between the two halves, which would then be pressed together, to create a thin liquid water surface at the bonding point. The cubical assembly would be placed on it side and the aluminum withdrawn (before it froze in place!), allowing the weight of the upper block to provide pressure to the bonding surfaces. In a short time, the lower internal temperature of the ice would re-freeze the water at the bonding surfaces, since air is excluded by the water, reconstituting the original whole block.

I like it, but the heat capacity of aluminum foil is nearly zero. It would seem to me that it would not hold enough heat long enough to melt much of the ice, if any ((25 °C) 24.200 J/(mol·K) versus ice which is 2.3 times higher). Additionally, the mass of the ice is much higher than that of the aluminum by several orders of magnitude (even for a small cube).

I would agree that it would seem better to cleve the block into two some how and then let it refreeze after it has been seperated into two halves. I just don't know how to split it.

However, what if you could bore a hole in the block and pour water into the hole? If the water refreezes it would expand. If you shape the hole correctly it might split the ice block. A warm stick or rod might do the trick and just make the hole flask-like so that the neck of the hole is small and freezes first.

Hardy-har-harr; that's a good one. ;-)

If the refraction of the atmosphere were a reason, it should shift the apparent location instead of magnifying. It would be like a straw placed in a glass of water.