Brain Teasers
Detention Bound
In a high school science class, Jimmy was given 50 milliliters of water and 50 milliliters of ethanol. His task was to mix them together and then run an experiment on the mixture. When the teacher came to check on him, however, Jimmy's mixture only contained 94 milliliters. The teacher accused him of drinking some of the mixture in an attempt to get intoxicated and immediately sent him to the principal. Jimmy swears that he did not drink the mixture and that he didn't lose any of the liquids by any means. What happened to the other six milliliters, and how could Jimmy prove his innocence?
Answer
When liquids are mixed, the molecules can arrange themselves so that they fit together more tightly than either of the original, pure liquids. A good way to visualize this is to picture a box completely filled with billiard balls (representing large molecules). If you pour a small amount of sand (representing small molecules) into the box, the sand will fill the voids between the billiard balls. The mass in the box will increase, but the total volume will not change. This is how Jimmy could prove his innocence - if he weighs the mixture, it will equal the original weight of the water plus the weight of the ethanol.Hide Answer Show Answer
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Comments
weird but true- and staright from a book.
hmmmmmmm Liquid .... - evapouration
Cath, I believe that the phrase "he didn't lose any of the liquids BY ANY MEANS" covers evaporation. Thank you and have a nice day.
I find it hard to believe that someone (the teacher) who has run this experiment thousands of times wouldn't know this.
bobbrt,
I agree with Cath. Jimmy might not have know that he lost liquids through evaporation so of course he is going to swear it. Have a nice day yourself.
I agree with Cath. Jimmy might not have know that he lost liquids through evaporation so of course he is going to swear it. Have a nice day yourself.
Apr 27, 2002
I'm with pezda - while the puzzle part of the teaser may be accurate and interesting, the scenario in which you placed it is unrealistic.
Apr 28, 2002
If this is what happens when you mix them, how come it didn't happen to all the other kids?
Why are you people so cruel? I just wanted to bring a little splash of joy into everyone's life, and all I get is this vicious, unprovoked abuse. What, oh what, have I done to deserve this brutal tongue-lashing? I think I need a hug...
in the answer, it states that all liquids have a smaller volume when mixed...its only miscible liquids that this happens in
and i dont think it is as drastic as sand and billards balls
I quite agree, bobbrt. They are being most unfair. This was a trainee teacher in her first science lesson. Just the sort of fact that would not be thought of in that situation. I'll give you a hug, (if you're female.)
I'm with you all the way and my joy surged when I read your teaser. I'm angry now because of the unjust cruelty that has ruined my surge of joy.
Why thank you, missie, you're a sweetheart. And Frank, you can keep those hands to yourself. Bobbrt does NOT stand for Bobbie-joe.
Ever noticed how those that are quickest to criticise a teaser are often those that have never submitted a teaser themselves? I liked it.
And Frank, your wrong. It was a substitute, and the teacher forgot to mention the decrease of volume. Then, the substitue won't get in trouble and neither will anybody else. (In Frank's idea with the trainee teacher the trainee would be in trouble).
And, to those that don't think it would be as drastic with pool balls and sand then how about pool balls and MARBLES.
Hey ignore the bad comments Bobbrt! it's a really gd 1!! and u shud b proud!! rock on!! be happy!! n smile!!
=¬D Xx
=¬D Xx
Im more of a logic fan, but this was interesting too.
Good teaser. I'm wondering whether it would be correct to say that the water dissolved some of the alcohol. Nah! That would involve disassociation of some of the molecules. Hmmm?
Jimbo, this teaser would not work if the water hadn't dissolved the alcohol (or vice-versa). If the two liquids are insoluble in each other, then they wouldn't mix at all and there would be no volume reduction. So yes, there was definitely dissolving involved.
I think this is a great teaser. Most people don't realize that volumes are not held constant when two different liquids are mixed. And to comment on a previous comment, there are some situations in which the volume increases when two liquids are mixed because of repulsive forces. It so happens that water and ethonal are different sizes and attract each other, thus the volume decreases.
Why the fuss about the scenario? The answer is legitimate. Most of the criticism seems to be directed at the storyline. If all the teasers that contained unusual scenarios or fiction were disallowed, there would be a lot less teasers on this site, including MadAde's (where is Madadia?) and many of mine. A little creativity many times makes a teaser more enjoyable. I wonder how much of the criticism is really the result of not being able to solve the teaser.
Jimmbo, it doesn't dissolve the ethanol, it mixes with it. In the example the sand remains sand the balls remain balls, the balls don't turn the sand into sand pool balls (i.e. salt & water make saltwater). That is the definition of miscible (able to mix)
I think this teaser should be viewed as an educational tool and learn from it. Leave the debating to the politicians. My opinion...
I still remember these type questions in high school and college. Nice and easy for me,but still a great science question.
Fairly easy, interesting that so many people had to criticize the story. It is just a story around a valid scientific fact. Loved it.
Good teaser!
i didn't get it , but I am hard pressed to see where anyone's comments were cruel... I also wonder if "bbrobt"? is still with Braingle?
I just took an AP chem class yet I never learned this. VERY interesting.
This teaser easily draws ire because of the injustice of the situation. A teacher decides to give alcohol to a high school student?? Then he or she is too ignorant to know what happens during an experiment they assigned? And then when the teacher observes something unexpected they decide to jump to conclusions and accuse the student? Accuse them of trying to get drunk off of a miniscule amount of alcohol?
Sorry, but thinking about the ways the story sounds so wrong and unrealistic is more interesting than the answer...
Sorry, but thinking about the ways the story sounds so wrong and unrealistic is more interesting than the answer...
good teaser. Yes, that's how he could have proved himself innocent, but that doesn't mean that he actually was innocent .
nice one.. i worked in a lab and a new technician was baffled for hours trying to make a 70% solution of methanol.. 'the volumes not working" came screaming from the neighbouring prep room..
Interesting, but think the chemistry teacher would have known.
This teaser is for a limited group of people. You have to have studied science or at least know something about it to even try to answer it. I do not find the comments cruel either. It just leaves a lot of unanswered questions. Sorry, my opinion also!
Interest teaser - but something I know nothing about. Hate to admit that!
I happen to know Jimmy, he did drink it.
I too do not find the comments "cruel" as the submitter claimed. People were just pointing out the flaws in the teaser. I also found it implausible that the teacher would not have known this, or that other students would not have also mixed the two liquids.
Even if he were to drink it, Jimmy has partaken enough in the past that the 50ml (less than 2oz) of alcohol that the teacher gave them wouldn't even give him a buzz.
Even if he were to drink it, Jimmy has partaken enough in the past that the 50ml (less than 2oz) of alcohol that the teacher gave them wouldn't even give him a buzz.
HABS, I know your tongue was in your cheek there, but 2 shots of pure alcohol would give even a seasoned teenage binge drinker more than a buzz, I fancy. The 6ml he allegedly drank might not have, I grant you.
Cool teaser! I guessed the right answer, but had never heard this before. It's my "new thing learned today" for today!
I thought the story added color and humor.
I thought the story added color and humor.
I thought this was great! I didn't know this about ethanol, and I like the story. It's just a story, but in fact unreasonable and unjust accusations are something a lot of kids experience. Maybe some of the other commenters had a better school experience than I did.
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