Calling All Oppo Thermodynamicists (UPDATE!)

"ttyymmnn" (ttyymmnn) 01/29/2016 at 11:30 • Filed to: None

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I’m working with my 4th grader on his science project today. He did an experiment to see if a frozen cup of ice would thaw more quickly if it were sitting in a bowl of water versus sitting out by itself. The ice in the bowl of water thawed significantly faster. Why? I’ve got some sort of idea about how there being more surface area, or better heat transfer, or something. I’m not even sure what to search on the Google about it. Any ideas?

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UPDATE : Many thanks to all who helped out with this. My son won 4th place out of the entire 4th grade for his project.

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MountainRoadPhysicist > ttyymmnn 01/23/2016 at 11:35

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Water has a higher heat capacitance than air. The ice will be able to absorb more energy from a larger body of water than it would otherwise absorb from air in a similar amount of time. This would be no different if he placed the same amout of ice in an equivalent body of water to both the bowl and cup. Hope this helps.

MM54 > ttyymmnn 01/23/2016 at 11:38

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Combintation of a higher thermal capacity of water than air and the overall better heat transfer into it from the ice.

Air is actually a pretty good insulator if you can keep it from circulating.

Birddog > ttyymmnn 01/23/2016 at 11:38

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This should help.

“Because water has higher thermal conductivity than air. It’s the same reason that cold water feels colder and hot water feels hotter than air at the same temperatures- water can move heat in and out of your body faster than air can, and it does the same thing to ice.”

Found on Quora.com. It goes on.

“Basically, if you put an icecube in air or water, it will first cool down the thin layer of air or water immediately surrounding it, warming itself up in the process. At that point, the ice can’t get any warmer or melt anymore until that initial layer or water or air can get warmed up by the next layer out, which itself gets cooled down. The speed at which that happens in water is much greater than it is in air, so the ice melts faster.”

Sneaky Pete > ttyymmnn 01/23/2016 at 11:39

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What was the temperature of the water? What was the temperature of the air? We’re the cups identical?

You have multiple heat transfer processes going on in both cases - conduction through the bowl to the ice /cup is common, but in the case of the water, you are seeing conduction from the ice/cup to the water whereas in the case of the air you’re experiencing convective heat transfer.

ttyymmnn > Birddog 01/23/2016 at 11:40

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That’s awesome. Thanks. Do you have the exact link?

ttyymmnn > MM54 01/23/2016 at 11:41

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Air is actually a pretty good insulator if you can keep it from circulating.

Don’t confuse me. I’m a musician, not a scientist.

If only EssExTee could be so grossly incandescent > ttyymmnn 01/23/2016 at 11:41

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The ice feels more comfortable in water due to being the same substance and thus more freely shares its coldness with the water.

ttyymmnn > Sneaky Pete 01/23/2016 at 11:42

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What was the temperature of the water? What was the temperature of the air? We’re the cups identical?

Temp of water: whatever came out of the tap. Temp of the air: house thermostat is set at 68. Cups were identical, all had 300ml of ice. Bowls were different shapes (he tried tap water, salt water and sugar water). Not terribly scientific, but it’s only 4th grade.

XJDano > ttyymmnn 01/23/2016 at 11:44

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It's basically how a double lined glass works, it just does.

someassemblyrequired > ttyymmnn 01/23/2016 at 11:45

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Air conducts heat to the surroundings much more slowly than water does. Here’s a table: http://www.engineeringtoolbox.com/thermal-conduc… . It’s the same reason being in cold air isn’t near as bad as falling into cold water (just in reverse). It’s a bit more complex than that because there are some convection processes than can come into play depending on currents and the height of the ice. This is taking place in 3D, so with a cup shape it’s actually a relatively complex heat transfer problem. But the main driver is the difference in the conductivity.

Berang > ttyymmnn 01/23/2016 at 11:45

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Water both conducts and stores heat better than any other substance. I believe in science terms, water has the highest “specific heat” of any substance.

davedave1111 > ttyymmnn 01/23/2016 at 11:50

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Air is an excellent insulator. Water is not. That’s about it, really.

ttyymmnn > someassemblyrequired 01/23/2016 at 11:51

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So, according to that chart, the higher the number the better?

ttyymmnn > Berang 01/23/2016 at 11:52

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Don’t get all science-y on me. I’m only in 4th grade.

someassemblyrequired > ttyymmnn 01/23/2016 at 11:53

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Yep the way to read that is that water conducts heat about 20x better than air for a given temperature difference and distance.

ttyymmnn > someassemblyrequired 01/23/2016 at 11:57

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Thanks. I just read that 20x figure on another website.

PS9 > ttyymmnn 01/23/2016 at 11:57

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Everyone’s giving a rational answer backed up by observed science. Pfft. Who needs that crap? Here’s the real reason that happens; Ice and water are hot for eachother. They are the lannisters of chemical substances. Get’em anywhere near eachother and watch out!

It’s true that life on our planet is thanks in large part to the ice caps on the top and bottom of it, but it’s only a matter of time. Once the ice/water orgy begins and continues for about 100k years or so, we won’t have to brace ourselves because winter won’t be coming anymore.

ttyymmnn > PS9 01/23/2016 at 11:58

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Obviously, you want my son to fail 4th grade. However, it would be fun to write this explanation and see what the judges say.

gin-san - shitpost specialist > ttyymmnn 01/23/2016 at 11:59

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Correct answers have already been posted, but here is a site for reference and it must be correct since it’s from a university website... right?

https://van.physics.illinois.edu/qa/listing.php…

Birddog > ttyymmnn 01/23/2016 at 12:00

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https://www.quora.com/Why-does-ice-m…

After 20 years in HVAC you’d think I wouldn’t have had to look that up!

ttyymmnn > gin-san - shitpost specialist 01/23/2016 at 12:02

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Thanks for the link. I’ve done a bit of googling, and found lots of science-y answers, but the ones from Oppo have been considerably easier to understand.

ttyymmnn > Birddog 01/23/2016 at 12:05

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Thanks. I’ve been a musician for 40 years, and I still have to look stuff up. Basic stuff, like what year Mozart died. I have no idea. Or how many symphonies Haydn wrote. I know it’s more than 100, but the exact number? Look it up. That’s what Google is for.

PS9 > ttyymmnn 01/23/2016 at 12:15

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Well it’s not my fault your son’s teachers have brought into Nobama’s science lies. WAKE UP, SHEEPLE!

ttyymmnn > PS9 01/23/2016 at 12:45

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Alex Jones, is that you?!

Lossy > ttyymmnn 01/23/2016 at 13:28

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Air molecules are much further apart that water. Entropy is what I would google.

Manwich - now Keto-Friendly > ttyymmnn 01/23/2016 at 14:01

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Think about it car terms... why do we mostly use liquid cooling for most engines/motors (even Tesla uses liquid cooling) instead of air cooling?

It’s because liquid has better thermal conductivity.

And if liquid can help with cooling an engine, it can also help with ‘warming up’ a cube of ice.

Manwich - now Keto-Friendly > PS9 01/23/2016 at 14:05

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“They are the Lannisters of chemical substances”

Exactly! Hot Lannister love... LOL

Manwich - now Keto-Friendly > MM54 01/23/2016 at 14:06

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“Air is actually a pretty good insulator if you can keep it from circulating.”

Which is why ‘thermoseal’ windows work.

ttyymmnn > Manwich - now Keto-Friendly 01/23/2016 at 14:35

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Ferdinand Porsche has just challenged you to a duel.

Manwich - now Keto-Friendly > ttyymmnn 01/23/2016 at 15:08

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I would win it before it even started... All I would have to do is point to the current liquid cooled 911 and he would sit down and start crying.

Then I would gently pat him on the head... and show him a picture of a Renault Dauphine:

ttyymmnn > Manwich - now Keto-Friendly 01/23/2016 at 15:19

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On the other hand, I have a friend who is an air-cooled VW aficionado, and he likes to recount the time he was driving with his dad on a very hot summer’s day, up some mountain somewhere. They passed numerous cars on the side of the road that had overheated, while they putt-putt-putted steadily up the hill with no problems. That was a long time ago, though. A couple of years ago, we drove over some desert mountain in southern California, they there were cisterns set up every half mile or so for people to top off their radiators. I’m certain those are vestiges from the 50s. Cars are much better at keeping cool these days.

Jcarr > ttyymmnn 01/29/2016 at 11:46

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This is why if you want to cool a can of soda/beer very quickly, you put it in a big tub of ice water, not just ice. The water will soak the heat from the beverage up super quick. It’ll go even faster if you add some salt.

Ash78, voting early and often > ttyymmnn 01/29/2016 at 11:51

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Answer is the same basic reason that the guys on Deadliest Catch don’t simply keel over dead after 5 minutes on the deck, even though falling into the (warmer) water would knock them out really quickly.

I think Newton called this the Third Rule of Discovery Channel, the first two being “Education will not be created on Discovery Channel after 2001" and “If you come to an impasse, check what’s on TLC”

Snuze: Needs another Swede > ttyymmnn 01/29/2016 at 11:55

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H=U*A*delta T

The rate of heat transfer equals the heat transfer coefficient (U) times the area (A) times the difference in temperature (delta T).

Basically the water has a higher U value so heat transfers faster from the water into the ice, causing it to melt.

That’s the 4th grade level explanation. If you wanted to get more technical there’s a lot more to this, such as mixed boundaries - ice floats, so some heat is transferred from the air as well, and the ice “in air” is also receiving heat transfer from whatever surface it’s sitting on. Also, if it’s a small bowl of water, as the ice melts it cools the water, so the delta T changes. In a normal room the volume of air is such that small amount of ice isn’t going to measurably affect air temperature. You’d also need to account for movement of the air and water as fluid moving over a surface changes the heat transfer rates.

OPPOsaurus WRX > ttyymmnn 01/29/2016 at 11:56

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cool thing, if you have a bottle/can of beer and need to have it cooled quick, wrap it in a wet paper towel and put it in the freezer. physics and shit makes it cool off way quicker than just putting it in the freezer by itself

Chariotoflove > ttyymmnn 01/29/2016 at 12:19

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Here’s a really 4th grade answer (I have a 4th grader; so, my brain is used to this mode):

Heat is expressed by the translational motion of the molecules in the substance. The hotter you make the liquid or gas, the faster they move. Their energy is transferred by the molecules bumping into each other. Water is way more dense than air, that is to say more molecules in a given unit space for a liquid than for a gas. So, the molecules bump into each other more often, and this means they transfer heat between them faster. Water has a tremendous capacity to absorb heat (this is due to hydrogen bonding between its molecules), and more water molecules are in contact with the ice than if you put it in air. So, heat is shuttled from the ice into the water much faster.

Congrats on his 4th place. Hurray! I love when kids get into science.

ttyymmnn > Chariotoflove 01/30/2016 at 09:44

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Yours is another excellent reply from the Opposphere. The explanations I got from Oppo were much easier for my 4th grader (and me) to understand than anything we found on the Web. His mom helped him with his project, and I helped his twin brother with a presentation/experiment on airplane wings and Daniel Bernoulli. We didn’t win an award, but Ice Boy did more hard, data driven science. I’m really happy for him.

ttyymmnn > Snuze: Needs another Swede 01/30/2016 at 09:47

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This definitely was not a carefully controlled experiment. We took four cups, filled them with 300ml of water, and froze them overnight. Then, we put one cup on a plastic plate, and one cup in a metal bowl of 1) tap water, 2) salt water, 3) sugar water. The metal bowls (one was a pot) were all different shapes, but they were roughly the same size and held the same about of water. Then, each hour, he drained the melted water out of each cup into a measuring cup and recorded the amount of liquid water. Then he put the water back in the cup. It was also neat to see how the ice in the water bowls melted in a cone shape, since the ice exposed to the air melted more slowly than the ice below the surface of the water.

ttyymmnn > Ash78, voting early and often 01/30/2016 at 09:49

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Answer is the same basic reason that the guys on Deadliest Catch don’t simply keel over dead after 5 minutes on the deck, even though falling into the (warmer) water would knock them out really quickly.

I like this comparison. The other morning, as we were walking to school, he asked why it didn’t feel as cold as the earlier morning as it did that day, even though the air temperature was lower. Well, there’s no wind today....

Chariotoflove > ttyymmnn 01/30/2016 at 12:21

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That’s why I like Oppo. I meet people like you.

This made me remember the science fairs I did with my dad. Good times.

ttyymmnn > Chariotoflove 01/30/2016 at 13:15

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Oppo is an awesome place. I've found none better on the net. Lots of great, helpful, kind, non-judgmental folks. And there are always people here who know something I don't, and are willing to help in a non condescending way.

Rusty Vandura - www.tinyurl.com/keepoppo > ttyymmnn 01/30/2016 at 17:36

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Thanks to, or in spite of, his father’s best efforts?

ttyymmnn > Rusty Vandura - www.tinyurl.com/keepoppo 01/30/2016 at 17:40

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Mom helped Ice Boy (A). I helped his brother. We did ours on airplane wings and Daniel Bernoulli. It was a good effort, but not much for hard science and data interpretation. Bernoulli wants to do a proper experiment next year.

Rusty Vandura - www.tinyurl.com/keepoppo > ttyymmnn 01/30/2016 at 17:42

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Outstanding. President Trump will abolish Common Core and you won’t need to worry about it any more.

ttyymmnn > Rusty Vandura - www.tinyurl.com/keepoppo 01/30/2016 at 17:49

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They are building a new school about .5 miles from our current one. The new school will be a STEM academy, and they are turning ours into an arts academy. Even though I’m an artist, I’d rather they have the STEM. Either way, they’ll still have to do a science project. Ice Boy’s project will be competing in the citywide science fair next month.

Rusty Vandura - www.tinyurl.com/keepoppo > ttyymmnn 01/30/2016 at 18:06

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In my experience, the “academy” concept usually only means everyone takes the same elective, since graduation requirements are already widely set.

Snuze: Needs another Swede > ttyymmnn 02/01/2016 at 19:45

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Truth be told, I think that’s a pretty good experiment for a 4th grader. And honestly, this is how a lot of science and research gets done - you do a quick and dirty experiment, or observe results form experiments that are similar but not the same as what you’re looking to study, to see if it’s even feasible/plausible. Then you set up a detailed, controlled experiment.