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More ways to get Braingle...

Sibling Rivalry

Science brain teasers require understanding of the physical or biological world and the laws that govern it.


Puzzle ID:#27117
Fun:*** (3.07)
Difficulty:** (1.96)
Submitted By:bigSWAFF_69_Aus******
Corrected By:javaguru




Swaff is sitting at his desk, being cool, when his younger brother Geemiee walks up. Geemiee had recently been practicing his (fake) magical powers, trying to turn cheese into more cheese, so he believes he can beat Swaff in anything. He sets up a little competition, the first to get 5 ounces of water to freeze, will be proclaimed the coolest guy in their home.

They set up some rules, as follows:
-They both can only use normal water that comes out of their stainless steel faucet.
-They both use identical containers
-They both must use the same freezer, at the same time.

Now, Swaff realizes that if he were to lose, he would become less cool, he just doesn't roll like that. So, how can Swaff have the best chance of winning over Geemiee?


All Swaff has to do in order to be the winner is use hot water.

Geemiee, being less cool than Swaff, didn't know that water with a hot average temperature freezes faster than water that is at room temperature. The phenomenon that hot water may freeze faster than cold is often called the Mpemba effect.


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Nov 23, 2005

Gonna have to read up on this one, had heard it before but wasn't sure- That was too cool
Nov 23, 2005

I thought "Put salt in the other one's container"!
Nov 23, 2005

Haha, booler, that's against the rules!
Nov 23, 2005

Actually, Swaff, being cool, could probably break the rules

I've known this for a while, and didn't know how to "teaserize" it.... I finally figured it out.
Nov 23, 2005

Nov 23, 2005

What if Swaff had added his water (reg temp) to the container in stages, with the smaller amounts freezing faster, (also aiding in freezing the next batch poured on top.) Would that have worked as well?
Nov 23, 2005

No, because they had to freeze the 5 oz. at the same time.
Nov 23, 2005

But it just said they had to USE the freezer at the same time, not pour the 5 oz at the same time. Thus they would be using the same freeze during the same PERIOD of time, depending on whose froze fastest.
Nov 23, 2005

that was 'cool'. I was thinking the same as boodler, salt or vodka!
Nov 23, 2005

Man, that just makes me wish you COULD get vodka out of the tap

I was going to do one SORT OF like this, but using the fact that vodka doesn't freeze at the same temp. as water.
Nov 24, 2005

Swaffy, I got it a bit easily. Good job on the teasing of your teasers. It seems as if you search the web trying to come up with facts for teasers. Well, good job, get some more out here! (actually don't, because I want more than you!!!)
Nov 26, 2005

Sorry Swaff, but the Mpemba effect has been questioned and finally been proven wrong. The molecules in the hot water are moving faster than those in the cool water. Yes, true, the coldness of the freezer affects the warm water first, but they end up freezing at the same time. This has been proven.
Nov 28, 2005

People really seem to be striking out with melting and freezing water.

Although there have been a few documented cases of the Mpemba effect working (that is, in particular circumstances), this is not an effect that can be observed at home in your freezer. The basis of the Mpemba effect has not to do with the thermal properties of water, but with external conditions surrounding the water and additional substances dissolved in the water.

Though a set of conditions could be replicated to cause hot water to freeze faster than cold, it is highly unlikely that these conditions would appear in the situation presented in this teaser.
(user deleted)
Nov 29, 2005

how about the kool kid does'nt use his container?

keep thinking!
you eventually beat me
Dec 12, 2005

Wrong, Wrong, Wrong, we did this experiment in 8th grade....Heat leaves water at a rate dependent on the difference of temperature of it and its environment. So... the hot water only loses energy faster while it is hot as it cools it slows....anyway blah, blah, blah if you don't adulterate it can't done...keep trying
Dec 12, 2005

I believe the what you are looking for is Einstien Law (or is it theory) of heating and cooling...or just a little basic thermodynamics
Dec 12, 2005

Oh, and I apologize for both spamming and my rudeness
Dec 13, 2005

they are right in the fact that hot water takes longer to freeze. good try though!
Dec 13, 2005

Go to water.html

Without the space
Dec 15, 2005

bigSWAFF 69, you're absolutely correct that the Mpemba effect is real (according to the best sources I can find). The issue is that it is very difficult to predict when it will happen, or what causes it. That being said, no one can reasonably expect to win in the situation you have layed out.

Bottom line, the Mpemba effect is much more complicated (hence the long explanation in the link you provided) Your teaser absolutely has reasonable foundation, but not a foundation that I would trust my home to, and not one on which I would bet my coolness!
Dec 24, 2005

I've known of this phenomi/nome for some time, so the answer was easy if not factual, conformation needed, if wanting to get technical.
Dec 24, 2005

I knew that! Years ago my uncle told me that hot water freezes faster than cold water. I paid attention...for once! Good teaser Swaff! Into my favs!
Dec 24, 2005

Dec 24, 2005

this is like way to easy but i still like it
Dec 24, 2005

Huh, now I really wonder... Well, it didn't say they couldn't add anything to each other's water or their own, it just said they had to use the same water from the same tap in the same container, so I thought maybe Mr. Kul added something to make his freeze faster. Thanks!
Dec 24, 2005

This has been standard fare in college physics classes, long before Mpemba first froze his ice cream. It has been a standing joke in our family that my mother's only D grade in her life was caused by her reluctance to accept that warm water can freeze faster than cool water. She took the physics class over to improve her grade, and actually failed it the second time!!! This was way before 1969.
Dec 24, 2005

I wouldn't be surprised if the hot and cold water in the same house had a slightly different mineral content, since the hot water picks up added impurities in the water heater, and they might freeze at different rates for this reason as well.

The story behind the M. effect is pretty interesting, by the way. Although the idea of hot water freezing faster than cold water was familiar to many ordinary housewives, it was a teenage boy in Africa who brough it to the attention of mainstream science.
Dec 24, 2005

I was thinking along the same lines as Boodler. I'm impressed. You must be a scientist.
Dec 24, 2005

The reason hot water freezes faster than cold is because of evaporation. Some of the hot water will evaporate (steam)resulting in a smaller amount of water to freeze.
Dec 24, 2005

It works. A bit hard to do, but it does work. And by the way
abcdefghijk mnopqrstuvwxyz to all from the Old China Hand.
Dec 24, 2005

How about accepting the fact that if one container were placed at the extreme bottom of the freezer, and the other near the top, the lower one has a better chance of freezing faster, as the air in a freezer is usually colder at the bottom? Especially if it is an older type freezer with no circulator fan in it. And that is FACT!!!!
Dec 24, 2005

Good one!! I got it!!!
Dec 24, 2005

I got this one, great one, easy and fun!
Dec 24, 2005

So much fun -- I had forgotten the hot water fact! big-swaff you are TOO COOL!
Dec 24, 2005

Hehe, cool.
Dec 24, 2005

The Mpemba effect is certainly no fact. The soundness of the phenomenon is highly disputed. What has been alleged by its believers is that under certain, very specific conditions the hot water will freeze faster -- not that it is a generally true effect.

Check out this site for a description. Then click on the "talk page" link at the top of the screen. You will note that in this open-source encyclopedia the entry for the Mpemba effect carries a disclaimer, stating: "The neutrality of this article is disputed because: Unverifiable Sources or References."
Dec 24, 2005

Oops -- here's the link:
Dec 24, 2005

alright, it stumped me, but you all have to admit, swaff sounds like a total geek.
Dec 24, 2005

(user deleted)
Dec 24, 2005

I heard also that this 'effect' was due to evaporation-but I'm skeptical even so. It would be influenced by the material of the container, if the hot water were to heat it-perhaps be hot even before it hit the freezer-and if it retained that heat, there's no way it wd freeze faster. Tho evaporation and heat dissipation might inhibit the brother's batch freezing...Great discussion tho, I love this stuff!
(user deleted)
Dec 24, 2005

Idiots! warmer water will not freeze faster. Given that there is a greater temperature differential (gradient - driving force for heat transfer) the hotter water may cool at a greater rate, but still needs to get down the starting temperature the cooler water began at. there fore it will take longer to freeze the hotter water, since it first needs to spend time getting cool, then from that point the same time to go to freezing. I can't believe whoever the science guy at this site is, is such a moron.
Dec 24, 2005

Think out of the BOX !

fastest way to freeze the water would be to splash it against the walls of the freezer !
Dec 24, 2005

Like most science questions, there are more than one answers. I thought that you should use hot water, but it said "they both must use normal water" so i was confused

Good job, anyhow.
Dec 24, 2005

Who knew?? Love the controversy it stirred up among the commenters almost as much as the riddle itself!!
Dec 24, 2005

what if you layed the container kinda side ways so there would not be that much depth? Or if you had other things in the freezer surrounding it? And like someone else said, putting the conthainer on the bottom? either way it was an interesting teaser and fun to read the comments...
Dec 24, 2005

i understand the concept but have never thought it was true

who knows
Dec 24, 2005

I knew it ,and you are absolutely RIGHT Great teaser my friend
Dec 24, 2005

I thought this was agreat teaser (evein if the M effect is disputed). Some of the commenters really need to stop taking these teasers so seriously and not get so worked up! Good job for creating some friendly controversy!
Dec 24, 2005

I knew where you were headed, but only believe notion of oldgrayfisherma. I, too, visioned that the best way to get a quicker freeze was to slosh water onto freezer surfaces. In the outside materials I noted that the effect is a sometimes thing which has been observed in sealed containers. How about some ideas on how one tests the waters in sealed containers for freezing?
Dec 24, 2005

All Staff has to do is to use hot water!That's what my answer was at first!When I looked @ the answer I saw that I was correct!That was a really good one!It makes you think like you were @
school or something like that!
Dec 24, 2005

I was going for maximizing the surface area, that's cool though, might have to try it out.
Dec 24, 2005

Dec 25, 2005

I liked this one.way to go bigSWAFF, you show GEEMIE how to do the water trick, and be cooool about it.
Dec 25, 2005

This is very true for all of you doubters. When the temp drops in the winter, the hot water is always the first to freeze. Anyone who has crawled around under the house to fix a pipe knows this.
Dec 26, 2005

I thought this teaser was kind of boring srrrry
Dec 26, 2005

I thought this teaser was kind of boring srrrry
Dec 26, 2005

I thought this teaser was kind of boring srrrry
Dec 26, 2005

I thought this teaser was kind of boring srrrry
Dec 26, 2005

I thought this teaser was kind of boring srrrry
Dec 26, 2005

Sorry, my copm. is slow and stupid
Dec 29, 2005

How cool. I thought it would be setting it next to the cold air vent in the freezer, which could also work Very cool, very informative, very good. In my favorites!
(user deleted)
Dec 31, 2005

The problem is that it won't work. You can try it yourself. I did. Suppose I start off with a cup of 70 degree water and a cup of 120 degree water. If I freeze the 120 degree water, it will go from 120 degrees to 32 degrees F. It can't get there without passing 70 degrees. Once it hits 70 degrees, it will take as long to cool as the original 70 degree water. i.e., it will take longer overall.

If you want to play with temperatures, a better way would be to start with 33 degree water. Or start with ice. Technically, it's a form of water, and the teaser does not say it can't start frozen. But the teaser implies that both start off the same. i.e., water is water. If you give the same name for what each person starts with, the assumption is that they are substantially similar. If you have to take the time to heat it first, it will slow you down even more.

When my kids were little, they did a science fair project on ice melting. One of the things they wanted to show was the effect of surface area. Although they were going for the opposite effect, they needed to create the ice in the first place in order to melt it. One of the things they did was to take two paper cups of water at the same temperature, and pour one on a flat plate. They put that in the freezer, as well as the paper cup with the identical volume of water. Needless to say, the water on the plate froze first, and also melted much faster at room temperature.

As for the Mpemba effect, many dispute it completely. Mpemba never even did his experiment with water. Even those who accept it also accept that it's not generally true. It may work in rare circumstances with very specific start temperatures under very specific circumstances (such as the amount of water evaporating lowering the volume sufficiently to freeze faster, or the surface freezing faster, thus making it appear to freeze faster, etc.) so even if it's theoretically possible, it's a safe bet that it will slow a person down substantially by starting with hot water in general.
Jan 08, 2006

And here I was thinking the "kool" guy was using multiple identicle containers to spread out his liquid to freeze quicker. If you go to the urban myth site and look under wife tales it discusses the hot vs cold thing. I'm won't.
Jan 12, 2006

As so many have stated above, your science is flawed at best.
Jan 12, 2006

I guess since so many of the previous commenters have... skewed ideas on thermodynamics I will explain. The hot water does indeed lose temperature faster than the cold, but using controlled variables, the cold water and the hot water will freeze at about the same time. Also, I'd like to point out that if the little brother had any sense, he would use cold water. The evaporation of the hot water would cause less than 5 ounces of it to freeze, and therefore the "cooler" brother loses.
Apr 28, 2006

May 01, 2006

Awesome teaser Swaffy! I ahould ahve known this really... good job I don't live with my Science teacher... Swaff has been proved cool once again
Jul 22, 2006

Hey, my dad knew this "way back when." He always filled the ice cube trays with hot water! He would be proud of your teaser!
(user deleted)
Nov 12, 2006

Hot water contains more dissolved air and so when it freezes there are more sights for ice crystals to form as the air comes out of solution. on the other hand you need to remove more heat to cool hot water I would say send this to MythBusters
Dec 24, 2006

The Mpemba effect is sketchy at best, but there are a few ways Swaffy can get the advantage:

1. They use identical containers, but there's nothing saying they can't use more than one container. Smaller volumes of liquid freeze faster, so if you split that 5 ounces into 5 containers, you'll have a much better chance.

2. Put his container closer to the freezer's fan.

3. Pour the water into his container after his little brother. The water would be pulled from further down in the water supply and therefore be a few degrees colder initially, leaving it with less of a temperature drop to make.
Dec 24, 2006

Well I had learned this before but still had fun reading your story.

I noticed you phrased the question "how can Swaff have the best chance of winning...". It doesn't always work, but certainly his chances are greatest if he uses hot water. You posed the question in a way that made it clear it wasn't a guaranteed win but does increase his chances.

I did this experiment as a teen because my dad didn't believe what I had learned in school. We did several experiments using different containers and various degrees of hot and cool water. In most cases they froze about the same time, but in a couple circumstances, the hot froze first.

Guess that makes me cool too!
Dec 24, 2006

A year on and we're back in the hot (and cold) water, still a good teaser through.

And to all, once again, a happy no "l". OCH
Dec 24, 2006

Ok, here's something reguarding this teaser for y'all to chew on. If I have two pots of water, of equal volume, boiling. One of which is on low heat, the other of which is on high heat. When you turn off the heat to each one at the same time, they both stop boiling at the same time, even though the water under the high heat is much hotter. Why is this? I failed college physics last semester, that's why I'm asking. LOL
Dec 24, 2006

pretty easy for this mornings teaser..
Dec 24, 2006

Fortunately, this is an easier one, this morning. Being neutral on this topic, because each explanation will come within seconds of each other. Yet, this is still a Totally Awesome teaser! Keep them coming! And everyone have a marvelous few weeks, too!
Dec 24, 2006

Good teaser - and I will try it with my grandchildren. I love the teasers, but I really enjoy everyone's comments! some interesting thoughts out there! and happy No "L" to you, too, OCH!
Dec 24, 2006

My mother told me about hot water freezing faster than cold, that was before the mpemba effect was even thought of.
Dec 24, 2006

A good one, I didn't know that.
Dec 24, 2006

An easy one, but not too boring. I thought of salt first, and then hot water popped into my head.
Dec 24, 2006


Dec 24, 2006

I thought it was well written. And quite a fun tearser.
Dec 24, 2006

very good teaser. i got it right after thinking about salt. from my science class, we learned that hot water does freeze faster because when the water is hot, the molecules are already distanced apart. when the water is cold, the molecules are closer together and have to spread out to form the ice.
Dec 25, 2006

lmfao... i didnt get the answer but it made me laugh. i sit at my desk all the time and be cool. hahahahahaha :]
Dec 25, 2006

I never knew this. Now I do.
Dec 27, 2006

Huh. Weird but cool.
Dec 28, 2006's been said before...As I talked with many science majors we have all come to agree that cold water in fact freezes faster that hot. The same goes for boiling. Hot water boils faster...because it's halfway there.
Use a car...It's harder to stop a car going 70 mph than a car going 30. It takes more energy. In this senario the cars are the particles in water to be frozen...70 being hot and 30 being cold. In the same manner...It is easier for a car going 70mph to speed to 100mph than a car going 30mph...again from the required energy. In this senario the cars are the particles in water to be boiled...70 being hot and 30 being cold.
Dec 29, 2006

Swaff remember me, tamjp? Well anyways hey! hi! and kudos on this teaser. Why did you drop out of the comment conversation?Thats the best judge of a teaser . if it sends people web searching for intel and data to take the time in comments to debate well Good Job! That is what makes this site great! PEACE
Jan 02, 2007

Good teaser, good trivia that I already knew about -- though I didn't know the name of the effect, and I didn't know about the disputes over it. Wow!! What fun it was to read the comments on this one, and all the links people posted!

Cheers to scientific inquiry!
Jan 09, 2007

It's INCREDIBLE that only 3 comments out of 88 pointed out the FACT that the recipient with hot water first has to cool down to the temperature of the cold water!

If the material is the same and the geometry is the same (as stated in the teaser) then it is just an energy balance! The hot water has to get rid of more energy! (I don't care about what happened before, but as soon as the hot water gets the same temperature as the cold water, then the heat transfer rate is the same for both samples!)
Aug 12, 2007

This was a great teaser. Very funny also!
Sep 14, 2007

sorry, but the myth isn't true. It's been disproven on several shows, including'myth busters.
Think about it. hot water must cool down to the temp that the other water started at, then cool from there to freezing at the same rate as the other. The other water started there, and had a head start.
Dec 14, 2007

great teaser, I knew that kindda
Feb 18, 2008

i science question is really good!!!
Feb 18, 2008

this science question rox!!!
Mar 06, 2009

Although I know of the Mpemba effect (although I didn't know that name before), I don't believe it to be true except under perhaps very specific conditions. The total amount of energy to exchange and the fact that the hot water must at some point have the same average temperature as the cold water would seem to defy the laws of physics. It was clear this was the answer you were setting up, but I went a different route that will actually work.

I was surprised that none of the previous 94 comments had what I thought was the easy and obvious approach that would work: put the container in the freezer before adding the water. The water added to the pre-cooled container will start freezing quicker than the water place in the room temperature container. Better yet, put your container in the freeze and the other container in the oven.

Dec 24, 2009

Sorry, but the Mpemba effect only happens under rare and specific conditions and is not a generalized or consistent effect for water. Therefore the most correct answer is to use cold water.

Still - water is such a cool and tricky substance though!
Dec 24, 2009

Tried this when my kids were small, and the cold water always froze first.
Dec 24, 2009

Dec 24, 2009

As I'm not very scientific, I thought it was the same answer except cold water. Great teaser!
Dec 24, 2009

cool! U learn something everyday!!
Dec 24, 2009

Dec 24, 2009

Yeah, the science behind this is flawed, but it's not like there's anything that can be done about it.
Dec 24, 2009

I have a simple answer that doesn't involve the Mpemba Effect. Swaffy should put his container in the freezer so that it spreads out the water as much as possible and Geemiee's container so the water is as spherical as possible. The greater surface to volume ratio will allow the heat to penetrate to the middle faster, allowing it to cool quicker. This would be much easier if the containers had lids, but most freezers have enough stuff that I'm sure he could get it to lean without falling over.
Dec 24, 2012

I thought I was being funny when I said to myself, "Oh just use hot water." However, I did not think that was right and I was just being silly. Turned out to be correct.
Dec 29, 2012

Foul! The Mpemba effect is spurious and will occur only under specific conditions that are outside the scope of the stated puzzle.
Dec 31, 2012

Wasn't sure what qualified as normal water, so I figured salting one wans't outside of the parameters. but after seeing the anser, i get it now. I will use what i just learned more in life.
Dec 24, 2015

Didn't even have to look at the answer. I guess I remember some things from skool.

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