Today I was shown an ice cream scooper (made by Tupperware) that I was told had the unusual property of being able to cut through frozen ice cream more effectively than other scoops by somehow melting the ice cream in its immediate vicinity. We tested it by putting a regular ice cube in the scop and watching it melt. It indeed appeared to melt quite a bit faster than one would expect.
Can anybody give a short primer on the physics behind this?
Well, I’ll take a stab at it. (more of a WAG)
I know the plates that defrost meat faster work through some sort of convection. In allowing the air to flow underneath the meat (little grooves in the plate) they somehow transfer heat more efficently.
I would say that this Ice Cream scoop might have some similar grooves in it, and allow the air currents to warm up the ice cream more efficently, thus allowing your scoop to cut through it.
I always had a cup of warm water nearby to dip the scoop in before using.
I bet I know what your talking about… its an aluminum scoop that is hollow and has a plastic insert (plug) in the end of the handle. They have water in them. The water inside the scoop keeps the scoop from reaching freezing temps, for the amount of time that your scooping anyway.
Those are the ones that I have seen.
This is another WAG, but I would guess that the scoop is made of a material that is good at transferring heat into the ice cream. Was it a metallic material? Metals conduct a lot better than something like plastic. Another thing that could make a difference is the specific heat of the material. If the metal has high specific heat then when it is in contact with the ice cream, a lot of heat would be transferred out of the metal to cool it to a temperature closer to the temperature of the ice cream. This heat would melt the ice cream directly contacting the metal.
Is this the item?
http://order.tupperware.com/coe/app/coe$www.show_item_detail?fv_item_number=10043202000
If so, i believe it’s as described by Whammo.
I believe it’s the same ice cream scoop originally made by Zeroll and now widely copied (The Pampered Chef sells its own version, too). The Zeroll web site is woefully short of information, but those fancy-pants at Williams-Sonoma say it contains antifreeze. By my reckoning, it’s either that or at least some other material that doesn’t solidify at 0 deg. C - I know this because I’ve stuck one in a freezer and then tested it. It still works, just not as well as a room-temperature scoop (and yes, putting it in warm water makes it work better yet). Anyway, it’s made of aluminum, which is an excellent heat conductor. If you pay more, you get the Teflon-coated model.
I’m not certain that it’s water as opposed to another liquid. But if it’s working after a few hours in the freezer, that’s due to the efficiency of its physical shape, not the liquid inside.
E.g.(actual temps here are questionable), if your freezer’s set at -10°C, and ice cream freezes at -5°C, the -10° scoop isn’t going to be conducting any heat from the liquid to the ice cream. In fact, the reverse will happen, with the contact layer of ice cream staying frozen longer due to the presence of the liquid.
That’s if it’s antifreeze. If water, the scoop should be essentially 0°C, with a negligable but positive conductance of heat from the water to the ice cream.
Actually, I’m not sure of that. Somebody set me straight here, can you suck heat from frozen water?
I wouldn’t think that the water idea would work either, but the ones I have seen are filled with water. When I asked the salesperson why not anti-freeze they said they didn’t know.
Uh, maybe it is water. If you shake the scoop at room temperature, you can hear the liquid inside sloshing around. I just pulled the scoop out of the freezer (having put it in again right after last night’s post) and there’s no sloshing. So, frozen liquid inside. Yeah, I forgot to check that in my earlier experiment.:o
My question to you Antifreeze advocates is this. Why the hell would antifreeze make a difference? Antifreeze doesnt radiate heat. It’s still below 0 Deg Celcius if you leave it in the freezer… just no frozen. If your going that route, just fill it with alcohol.
The fact that is works is that the water is a higher temperature then the ice cream… the aluminum scoop is a great conductor of heat and the water keeps it warmed up more then the icecream for a greater length of time. If you froze it (antifreeze or not) it wouldnt work any better then a regular spoon.
I worked in a gourmet ice cream store when I was in high school, and we used those scoops. People were always amazed at how quickly we could hack through ice cream.
I was thinking about this and going along with Whammo said, another reason that something like alcohol or anti-freeze isn’t used it that if the scoop cracked somehow the company wouldn’t want anti-freeze leaking out into someone’s ice cream. Water is harmless and works well.
Erg, you guys are making me drag out my Heat Transfer textbook. I think thermal conductivity is more important than temperature here, and the tables in the back of the book tell us:
[ul][li]Ethylene glycol (antifreeze), 0°C: 0.242 W/m °C[/li][li]Ethylene glycol, 20°C: 0.249[/li][li]Water, 0°C: 0.566[/li][li]Water, 20°C: 0.604 (actually, for some reason they used 70°F here, but close enough)[/li][li]Aluminum (pure), 0°C: 202[/li][li]Aluminum, 20°C: 204[/ul][/li]It says nothing about alcohol, but we see that even at the freezing point, water still conducts much better than antifreeze. Another nail in its coffin. And the scoop works better than a spoon because steel, in its various forms, ranges from about only 15 to 70, much worse than aluminum. Now, silver has a thermal conductivity of 410 at 0°C, twice that of aluminum, so really what we all need are silver ice cream scoops, hehe.
Another thing, yes, these scoops have grooves cut into the “bowl” of the scoop, but I’m not how much convection flow takes place there. Rather, I think they provide smaller contact area between the scoop and the solidified ice cream, further making it release better.
I think it wouldn’t really matter what’s inside if the scoop cracked and leaked liquid all over the place. Anyone in his right mind would throw out the rest of the ice-cream regardless. At least, I hope so!
Anyone in his right mind would know McDonald’s coffee is hot, too, but that sure doesn’t stop the lawsuits. I’d guess whatever is in the ice cream scooper is non-toxic, just to be safe.
It seems that you guys are assuming the liquid is just there as a filler material with a large specific heat. I think the liquid is actually used to move heat by convection, which is often more efficient than conduction. That is, the water circulating inside the scoop moves the heat to the cold surface. If the liquid freezes, it would stop moving, and no more convection. So using anti-freeze would make sense, but perhaps water stays liquid long enough, and is much safer to have around food.
I think I will wait untill Aramis comes back and confirms your theories. The OP does not state anything about a plug with liquid in it. Wouldn’t the physics behind that be a little bit more obvious?
Under normal use, i.e. not freezing the scoop beforehand, the water in the handle should not freeze. The way the scoop works is to transfer thermal energy from the water to the metal scoop, to the ice cream, melting the ice cream, making the scooping easier.
A great deal of energy is released when water freezes, even though the temp remains at 0 centigrade, I believe that’s called the Latent Heat of fusion. As the water is freezing, the scoop will still be able to transfer this energy to the ice cream, albeit less than normal given the small temperature difference between the water and the ice cream.
Antifreeze will make this situation worse, the water will not freeze, rather the temp will continue to drop below 0 centigrade, further reducing the temperature gradient, and never releasing the latent heat. You would be much better off with pure water.
First time poster…so please forgive any upcoming mistakes. I’m not a physics teacher, but I was a college student. On more than one occasion, my roommates and I would watch infomercials. Our favorite was the Miracle Thaw. After many a night of amazement, we ordered it.
I am not sure if this “Magic Scoop” is made from the same material, but it would make a lot of sense. Yes, the Miracle Thaw did work. We melted many an ice cube on it. How it worked, I am not sure. When asked by an equally astonished friend how it worked, we would always quote the infomercial…“it’s made from a space age polymer”.
Not sure if I was of any help…but maybe someone can research the Miracle Thaw and what material that was made from.
To all the Dopers out there…thank-you for the posts…my high school students love the lil tidbits of knowledge that I impart on them.
Rufus
I didn’t realize a question like this would generate so much commotion.
I don’t have access to the scoop in question right now so I can’t say if it is liquid filled or not. It is fairly heavy for its size, so it’s either solid metal or possibly liquid filled. I’ll check at the next opportunity to see if I can determine which. The one I saw definitely did not have grooves cut in the bowl unless they so small as to be nearly invisible to the naked eye.
The idea about a material with a high specific heat sounds reasonable, but is that just aluminum or some special alloy? If it were just aluminuum, I’d think that the property in question would have been identified some time ago and not seem so mysterious.
I suspect it comes down to a material that is able to retain a large amount of heat and transfer it outwards at a rate fast enough to heat the material in the immediate vicinity as it passes through, but not so fast that it rapidly loses its own heat.