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Does it turn into energy? Does it go into the toilet?
October 3, 2013 11:01 AM   Subscribe

In a TEDx talk from Queensland University of Technology, Ruben Meerman asks and answers a question many everyday people seem not to know the answer to: When you lose fat, where does it go?

Note: there is a typo in one of his equations during the talk. Don't let it stress you out.
posted by ocherdraco (101 comments total) 24 users marked this as a favorite

 
I thought that was obvious: it's excreted in all the ways that normal food is excreted after you process it: as carbon dioxide in your breath, and as water and waste chemicals in your urine. Your body processes the fat as if it was food.
posted by Chocolate Pickle at 11:12 AM on October 3, 2013 [4 favorites]


TED's really tackling the tough problems now. Next up: How is babby formed?
posted by meehawl at 11:16 AM on October 3, 2013 [65 favorites]


This is interesting; thanks for posting it.
posted by likeatoaster at 11:16 AM on October 3, 2013


Yeah, but the idea that you can lose significant amounts of solid mass in the form of a gas like CO2 is totally fucking mindblowing, and this guy does a pretty good job of both convincing you that it's true and playing up the totally-fucking-mindblowing aspect of it.

(The flip side is even weirder, at least for me. Tree trunks are made out of air. When trees get bigger, they mostly do it by pulling C, O and H out of the air in the form of various gasses, not by taking in anything solid or liquid. That one still makes my head spin around in little circles when I think about it too hard.)
posted by Now there are two. There are two _______. at 11:21 AM on October 3, 2013 [31 favorites]


How is babby formed?

This meme always pissed me right the hell off. Someone has curiosity about how the world works - someone who maybe isn't as educated or articulate in the written word as they'd like to be - and they are mocked cruelly by basically the entire internet for the crime of trying to learn something new.
posted by Slap*Happy at 11:22 AM on October 3, 2013 [51 favorites]


(I was actually thinking of asking on Ask what, really really specifically, happens when you lose weight but I thought it would be too gross)
posted by 2bucksplus at 11:26 AM on October 3, 2013 [1 favorite]


Yeah, but the idea that you can lose significant amounts of solid mass in the form of a gas like CO2 is totally fucking mindblowing...

I haven't seen the talk yet, but I came to this realization on my own pretty recently. Since I've been exercising and dieting for the last few months, I keep a close eye on my weight. A number of times I've gone to bed right after weighing myself, and weighed myself again immediately upon waking. In many cases, I've lost almost a pound of weight without, um, deliberately shedding mass. I used to think the scale had a problem, but then I thought about exhaling and wondered "where does the C in CO2 come from?" That's when I realized that I was exhaling food.
posted by Edgewise at 11:26 AM on October 3, 2013 [5 favorites]


Yeah, but the idea that you can lose significant amounts of solid mass in the form of a gas like CO2 is totally fucking mindblowing, and this guy does a pretty good job of both convincing you that it's true and playing up the totally-fucking-mindblowing aspect of it.

You've obviously never seen me panting after an ass-kicking run.
posted by The Whelk at 11:27 AM on October 3, 2013 [6 favorites]


I imagine you also lose a certain amount of water via evaporation from your skin and membranes.

What's up with the seventeen teaspoons of sugar in a soft drink? This guy was spooning heaping soup spoons of sugar into a pint glass and filled it half up, which I think would be about 200 ml of sugar. But according to google, 17 teaspoons is about 84 ml. Was that just hyperbole?
posted by rustcrumb at 11:30 AM on October 3, 2013 [1 favorite]


(The flip side is even weirder, at least for me. Tree trunks are made out of air. When trees get bigger, they mostly do it by pulling C, O and H out of the air in the form of various gasses, not by taking in anything solid or liquid. That one still makes my head spin around in little circles when I think about it too hard.

Yeah, totally. I'm fond of pointing out (to anyone who will listen) that every single C atom in every single molecule in that redwood over there came out of the...air.
posted by Didymium at 11:36 AM on October 3, 2013 [4 favorites]


I'm kind of surprised that he made a glaring mathematical error when calculating the weight of the hydrogen molecules. 1.0079 * 104 = 104.8216, not 95.996. The end result was roughly the same, but still, how did that slip through?
posted by grumpybear69 at 11:39 AM on October 3, 2013


We learned this in high school science FFS.

The most annoying thing about the TED fuckers is that they think they invented common sense etc. and then pat themselves on the back for it.
posted by KokuRyu at 11:40 AM on October 3, 2013 [20 favorites]


The most annoying thing about the TED fuckers is that they think they invented common sense etc. and then pat themselves on the back for it.

The thing about common sense is, it's uncommonly used.
posted by EmpressCallipygos at 11:44 AM on October 3, 2013 [8 favorites]


rustcrumb, I don't think that's actually a pint glass. It seemed a little misleading in that the glass wasn't the same size as the bottle of sugary drink (600ml or 20oz).

The conservation of mass stuff wasn't surprising, but the fact that it was excreted through the breath was interesting. It messes with the common sense that solids going in are solids going out (presumably partially because it's not obvious that gasses have mass without a bit of education).
posted by Renegade Duck at 11:44 AM on October 3, 2013 [2 favorites]


Someone has curiosity about how the world works - someone who maybe isn't as educated or articulate in the written word as they'd like to be - and they are mocked cruelly by basically the entire internet for the crime of trying to learn something new.

XKCD 1053
posted by bondcliff at 11:45 AM on October 3, 2013 [25 favorites]


The most annoying thing about Mefites, on the other hand... ;)

Also, to paraphrase Whelk...

You've obviously never seen me panting after an ass-kicking run walk.

FTFM
posted by symbioid at 11:45 AM on October 3, 2013 [1 favorite]


Was that just hyperbole?

I can't watch the video now, so I don't know how big the soft drink in question was, but a 12 oz can of Coca-Cola has 39 grams of sugar. According to this weight-to-volume calculator, 39 grams of granulated sugar has a volume of 46 milliliters, or slightly more than 9 teaspoons. To get to 200 ml of granulated sugar (about 40 teaspoons), you'd need about 52 oz of Coke.
posted by Partial Law at 11:46 AM on October 3, 2013 [1 favorite]


What's up with the seventeen teaspoons of sugar in a soft drink? This guy was spooning heaping soup spoons of sugar into a pint glass and filled it half up, which I think would be about 200 ml of sugar. But according to google, 17 teaspoons is about 84 ml.

It's weird to use volume to measure sugar. You should use mass instead. The volume will depend entirely on grain size: a given volume of powdered sugar has a whole lot more sugar in it than the same volume of granulated sugar.
posted by mr_roboto at 11:47 AM on October 3, 2013 [3 favorites]


When trees get bigger, they mostly do it by pulling C, O and H out of the air in the form of various gasses, not by taking in anything solid or liquid.

Of course fire makes a similarly amazing conversion, and does it a lot faster. Overnight my wood stove can convert 40 pounds of oak into a few ounces of ash, a few grams of smoke, and a whole lot of gaseous stuff.
posted by jon1270 at 11:48 AM on October 3, 2013 [5 favorites]


We learned this in high school science FFS.

The most annoying thing about the TED fuckers is that they think they invented common sense etc


If it's common sense why would you need to learn it in high school?
posted by bondcliff at 11:49 AM on October 3, 2013 [11 favorites]


FYI the video link uses Youtube's "embed format":

http://www.youtube.com/embed/NGKLpYtZ19Q

That happens to defeat Metafilter's YT detect-fu. Better to use the regular URL format:

http://www.youtube.com/watch?v=NGKLpYtZ19Q

... which then gives you the little embedded arrow, in addition to the usual fullblown YT controls.

Back to the snark and bicker!
posted by intermod at 11:49 AM on October 3, 2013 [1 favorite]


Yeah, but the idea that you can lose significant amounts of solid mass in the form of a gas like CO2 is totally fucking mindblowing,

It is common enough that it shouldn't be. I have never heard of anyone marveling with wood or charcoal is burned - the remaining ashes are much less mass than the original fuel. Similarly, while it is not solid, I don't think many people wonder what happens to the gasoline they pump into their cars.
posted by Tanizaki at 11:50 AM on October 3, 2013 [1 favorite]


When YOU lose weight, where does it go?

I swear to god right on my ass.
posted by BlueHorse at 11:50 AM on October 3, 2013 [12 favorites]


That's when I realized that I was exhaling food.

It's the other way around for me.

Nom.
posted by notyou at 11:52 AM on October 3, 2013 [4 favorites]


oh, sweet - I was literally just having this conversation with someone the other day, and neither of us were sure about it.
posted by jacalata at 11:55 AM on October 3, 2013 [1 favorite]


I burn mine off in the form of body heat. Then again I run about 105 normally and eat sticks of butter and crisco for lunch.
posted by The 10th Regiment of Foot at 11:57 AM on October 3, 2013


Well you're exhaling the part that isn't turned into heat and work.
posted by Mei's lost sandal at 11:58 AM on October 3, 2013


With trees of course, there's a giveaway. If the tree got its mass from the soil instead of air and water, it'd end up sitting at the bottom of a big hole. And it would probably burn as well as soil does.
posted by pipeski at 11:58 AM on October 3, 2013


Wrong.

It goes into a pocket of interdimensional space.

Where it waits.
posted by MrVisible at 11:59 AM on October 3, 2013 [14 favorites]


Well you're exhaling the part that isn't turned into heat and work.

No, you're not converting mass into energy. You're extracting energy from chemical reactions, which don't result in any change in mass. Unless you're Iron Man, maybe.
posted by pipeski at 12:00 PM on October 3, 2013 [4 favorites]


What, no blowing chunks jokes?

What's also interesting -- if I've got my pop biology right -- is that your fat cells are much more willing to multiply than disappear. So when you gain weight, your fat cells grow, and eventually divide. When you lose weight, fat cells shrink but don't disappear. Which does seem to make it clear why people who lose weight gain it back more easily than they put it on in the first place; all those cells are still there, ready to store fat at a lower metabolic cost than when they were first created.
posted by George_Spiggott at 12:00 PM on October 3, 2013 [2 favorites]


That's when I realized that I was exhaling food.

To be fair, what you're exhaling is the waste product. It's truer to say you're exhaling shit.
posted by iotic at 12:01 PM on October 3, 2013 [1 favorite]


pepeski: right of course (blushes).
posted by Mei's lost sandal at 12:01 PM on October 3, 2013


It's truer to say you're exhaling shit.

OK, OK, you could have just told me to pop and altoid or something!
posted by The 10th Regiment of Foot at 12:02 PM on October 3, 2013 [4 favorites]


iotic: "To be fair, what you're exhaling is the waste product. It's truer to say you're exhaling shit."

So when is your Ted Talk?
posted by boo_radley at 12:03 PM on October 3, 2013 [7 favorites]


This reminds me of a letter to the editor years ago where some guy with a supposed chemistry background "debunks" the fact that a gallon of gas can produce XYZ amount of CO2 (by mass) because THERE AIN'T THAT MUCH CARBON IN THERE. OXYGEN HAS MASS BRO
posted by lordaych at 12:06 PM on October 3, 2013


No, you're not converting mass into energy.

pepeski: right of course (blushes).


You were right the first time, Mel's.

The amount of mass converted is tiny, but definitely not zero-- E=mc2, remember.
posted by jamjam at 12:09 PM on October 3, 2013 [1 favorite]


"how is babby formed" was a rhetorical question in a semi-literate screed conflating abortion and child murder
posted by idiopath at 12:11 PM on October 3, 2013 [9 favorites]


i bet this is an interesting video but the comments have assured me that enjoying it would mean i am dumb and didn't go to high school, so i'd better not watch it

i get to skip a lot of stuff this way, actually
posted by a birds at 12:14 PM on October 3, 2013 [4 favorites]


TED's really tackling the tough problems now. Next up: How is babby formed?

It should be noted that this is TEDx, which is kind of bush league.
posted by planetesimal at 12:19 PM on October 3, 2013 [5 favorites]


The big question at least for me is, how do I stay the same weight that I'm now? That basic biochemistry equation is as useless a truism as 0=0 if you try to understand how the body (and the mind too, I guess?) keeps its weight in balance.

I was eating Nutella straight from the jar as I watched the video. It was somehow really good and a bit disgusting at the same time. The Nutella I mean. The video was fun, in the way that chemistry lessons never were in high school. All our experiments would take ages to prepare, then fail miserably. This guy does his experiments in like ten seconds, and they all succeed!
posted by ikalliom at 12:20 PM on October 3, 2013


I was totally expecting a Breathairian pitch towards the end of this video so the climate change diatribe came as a surprise.

Also, in the spirit of maybe 10,000 people learning this one today: TED is the original program with 'big ideas' and big names and real groundbreaking/bleeding edge stuff. TEDx is akin to franchises or local programs. It's more like Toastmasters crossed with collegiate gen-ed courses.
posted by carsonb at 12:20 PM on October 3, 2013 [3 favorites]


GUYS! I was seriously this close to posting this to AskMe. Yusssss.
posted by spikeleemajortomdickandharryconnickjrmints at 12:20 PM on October 3, 2013


I was going to flag meehawl's post as noise and then I decided I'd better google first. I'm still going to flag the post, but as fantastic because it made me laugh my ass off and I needed that today.

The Ted talk was cool too.
posted by photoslob at 12:22 PM on October 3, 2013


The amount of mass converted is tiny, but definitely not zero-- E=mc2, remember.

Conservation of mass is a useful approximation in chemistry.
posted by pipeski at 12:27 PM on October 3, 2013


To be fair, what you're exhaling is the waste product. It's truer to say you're exhaling shit.

Well, I think we all knew that hot air and bullshit are basically the same thing.
posted by Copronymus at 12:29 PM on October 3, 2013 [2 favorites]


Conservation of mass is a useful approximation in chemistry.

So it is, but when used categorically-- and therefore mistakenly-- to embarrass someone whose statement was actually perfectly correct, I feel obligated to point out that it is only an approximation.
posted by jamjam at 12:37 PM on October 3, 2013


The big question at least for me is, how do I stay the same weight that I'm now?

Step away from the Nutella is the first order of business
posted by thelonius at 12:43 PM on October 3, 2013 [2 favorites]


The big question at least for me is, how do I stay the same weight that I'm now?

Portion Control. e.g. I loves me some Nutella, in fact I have it on my PB&J&N lunch sandwich every day. However if you're eating it straight from the jar instead take a soup spoon full and then close the jar.
posted by achrise at 12:49 PM on October 3, 2013


I think transcending the laws of biophysics will be easier for me. Seriously though, I've been about the same weight for 15 years but in the back of my mind I worry that the universe is eventually going to find out about my eating habits. And then it's going to be a rough ride down.
posted by ikalliom at 12:58 PM on October 3, 2013


it turns in to earwigs that scurry away while you sleep.

fyi.
posted by rebent at 12:59 PM on October 3, 2013 [2 favorites]


You are what you eat except what you excrete.
posted by srboisvert at 1:06 PM on October 3, 2013 [1 favorite]


So he talks about Sugar (Carbohydrates) and Fat, but what about Protein? Does that work the same (is protein just a mix of Carbon, Hydrogen, and Oxygen too)?
posted by zinon at 1:07 PM on October 3, 2013


Hm, I kinda think E=mc^2 does not apply here and there is no conversion of mass to energy. It took energy to create the original bonds, the energy is stored, and then released when the bonds are broken. Since energy going in is the same as energy going out, M1+E1 = M2+E2 and there is no change in mass. I suppose I could be wrong, though.
posted by RustyBrooks at 1:15 PM on October 3, 2013 [2 favorites]


I already knew the answer, although I wasn't completely sure on the ratio of mass of CO2 and mass of H2O so thanks for posting.

I would comment on people's level of scientific education, but in a previous job there was a person at work who quite honestly believed that your weight wouldn't go up immediately after eating something. Really. Your weight would not increase despite putting food into your stomach.

We managed to convince her that it did, thanks to the work bathroom scales, but that pretty much reset my expectations of scientific knowledge.
posted by YAMWAK at 1:15 PM on October 3, 2013


How do I turn the extra proselytizing and fat shaming at the beginning into carbon dioxide and water?
posted by Apropos of Something at 1:22 PM on October 3, 2013


Now there are two. There are two _______.: (The flip side is even weirder, at least for me. Tree trunks are made out of air. When trees get bigger, they mostly do it by pulling C, O and H out of the air in the form of various gasses, not by taking in anything solid or liquid. That one still makes my head spin around in little circles when I think about it too hard.)

Actually, wouldn't the H (and some of the O) come from water, taken in by the roots? Photosynthesis consumes water, that's where the hydrogen in the hydrocarbon output comes from.
posted by Mitrovarr at 1:26 PM on October 3, 2013 [2 favorites]


how is it that i know all and others not?
posted by smidgen at 1:30 PM on October 3, 2013 [2 favorites]


Hm, this calls into serious question the Bethselamin anti-erosion program.
posted by jepler at 1:32 PM on October 3, 2013 [1 favorite]


Unfortunately, I know where *some* of the fat goes.
posted by markkraft at 1:37 PM on October 3, 2013


"Actually, wouldn't the H (and some of the O) come from water, taken in by the roots? Photosynthesis consumes water, that's where the hydrogen in the hydrocarbon output comes from."

Yup.

Also, here's an interesting tidbit: roots respire. In other words, they consume oxygen and produce CO2. It's only the leaves* that produce O2.

*or other photosynthetic sites, such as the modified stems of green cacti
posted by Xoebe at 1:39 PM on October 3, 2013


I was forced at several different levels of my education to memorize the enzymes and intermediates of the citric acid cycle (most of which I have forgotten), but none of my professors ever seemed interested in imparting the big picture of the carbon cycle. It wasn’t until years later that it suddenly occurred to me that plants don’t build themselves from dirt, they build themselves from air.

So he talks about Sugar (Carbohydrates) and Fat, but what about Protein? Does that work the same (is protein just a mix of Carbon, Hydrogen, and Oxygen too)?

Proteins are made of amino acids, which are mostly carbon, hydrogen, nitrogen, and oxygen. A few have sulfur. Think of them like biological Legos; they're a standard set of pieces used to build proteins. Our bodies can synthesize most of the amino acids from scratch (e.g., from carbohydrates), but it’s more efficient just to reuse the ones we get from ingested protein. There are also nine amino acids our bodies can’t make, and which we can only get from food (so-called essential amino acids).
posted by dephlogisticated at 1:52 PM on October 3, 2013 [3 favorites]


Actually, wouldn't the H (and some of the O) come from water, taken in by the roots? Photosynthesis consumes water, that's where the hydrogen in the hydrocarbon output comes from.

Good call. Yup, I misspoke.
posted by Now there are two. There are two _______. at 1:54 PM on October 3, 2013


Pretty basic concept articulately explained by Bill Nye: HEARTMELTING

Pretty basic concept articulately explained by TEDx person: INFURIATING
posted by Think_Long at 2:02 PM on October 3, 2013 [8 favorites]


Hm, I kinda think E=mc^2 does not apply here and there is no conversion of mass to energy. It took energy to create the original bonds, the energy is stored, and then released when the bonds are broken. Since energy going in is the same as energy going out, M1+E1 = M2+E2 and there is no change in mass. I suppose I could be wrong, though.

Hey there Rusty, E = mc^2 does apply here, it's just that the mass gain is so small that no one would bother to worry about it normally.

The fancy name for the result that E=mc^2 is the 'principle of mass energy equivalence'. It means exactly what you'd expect it to; that every increase in energy leads to an increase in mass. So every time you stretch a spring you make it a tiny bit heavier, or if you break a chemical bond you lose the tiny tiny amount of mass associated with it.

I know when people normally think of E=mc^2 they think of things like atom bombs or nuclear power, which are more obvious examples, but if you think about it everything else has to be included too. For example, if a radioactive atom decays to something lighter, and converts this mass into energy in the form of a photon, and then this photon is absorbed by the electrons surrounding another atom, the second atom has to gain the same amount of mass as the first atom or we lose the mass from the system.
posted by Ned G at 2:11 PM on October 3, 2013 [2 favorites]


Worth noting this is TEDx, which is kind of the poor man's TED talk. I've seen a few TEDx presentations that were essentially rather awkward sales pitches for products you might find in an infomercial.
posted by zardoz at 2:37 PM on October 3, 2013


Not quite all of the mass from the Citric Acid Cycle [Krebs Cycle to some] is exhaled as carbon dioxide. "In addition, the cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions."

And as others have noted an infinitessimally small amount of mass is lost in the form of energy. A seriously tiny amount. If I remember a long ago lecture correctly in any twenty four hour period the entirety of the Earth absorbs about eight pounds of sunlight.
posted by vapidave at 3:25 PM on October 3, 2013


This is all bullshit and none of you know what you are talking about. Fat is absorbed and transformed by the muscle most closest to it, so if you have a fat belly you do a bunch of situps and as your ab muscles vibrate they "break apart" the fat molecules, which then trickle down into the muscle fibers and are absorbed by the muscle and used for fuel. Muscles are basically just Sham-Wows.

Fat is also broken down by sitting in a sauna. The extreme heat causes your fat molecules to literally burst, releasing their water atoms as sweat and the rest of it is processed by the umm, kidney. The kidney and the livers.

You don't even really need to do anything at all. Certain apparatus will move your body about vigorously. This causes friction, which is really the best of both worlds: heat and vibration. Fat molecules EXPLODE and the best atoms are absorbed by your muscles, while the rest gets squirted out your pores and eliminated from the body.

These apparatus are very affordable on an installment plan, and can be folded easily away and stored beneath the bed or in the cupboard.
posted by turbid dahlia at 3:35 PM on October 3, 2013 [9 favorites]


I've seen a few TEDx presentations that were essentially rather awkward sales pitches for products you might find in an infomercial.

Or they were this. (Mirror of the video.)
posted by kmz at 3:38 PM on October 3, 2013 [2 favorites]


This was actually pretty informative I guess. I'm not sure why people are reading it as useless. But then my high school chemistry class was a nun setting a kid on fire soooo...
posted by Ghostride The Whip at 3:39 PM on October 3, 2013 [2 favorites]


in any twenty four hour period the entirety of the Earth absorbs about eight pounds of sunlight.

And if we released all that energy at once it would be roughly equivalent to a 200 kiloton thermonuclear bomb.

Every day.

On the staircase actually a lot more than that -- that's what it would be if we burned 8 pounds of liquid hydrogen via fusion. Only a small fraction of the hydrogen is converted to energy in an H-bomb. Shit.
posted by localroger at 3:45 PM on October 3, 2013 [2 favorites]


Clearly, we have work to do!
posted by planetesimal at 3:46 PM on October 3, 2013


New envelope suggests about 30 megatons. Yikes.
posted by localroger at 3:49 PM on October 3, 2013


Yep, via yet another approximation 1010 humans generating 50 to 100 watts each for 24 hours is in that ballpark. At that rate the human race goes through the equivalent of our entire global nuclear stockpile just breathing in about six months.

Kinda takes some of the shine off the idea of nuclear energy, don't it.

posted by localroger at 3:54 PM on October 3, 2013


And people say the machines in The Matrix were being inefficient.
posted by turbid dahlia at 3:59 PM on October 3, 2013


As impressive as that is, measured another way the sum total of all human metabolism is around 1014 watt-hours. But the total energy production of human industry is on the order of 100 petawatt-hours, or 1017 watt-hours -- three orders of magnitude more. Which I suppose is why we aren't planting fields of burnable crops to provide a carbon-neutral alternative to burning fossil fuels.
posted by localroger at 4:43 PM on October 3, 2013


We learned this in high school science FFS.

My catholic high school didn't have science. Plus I am old. When I was in high school there were only two kingdoms - fungi didn't have dey own crib yet. So, I vote yes to remedial biology FPPs.
posted by toodleydoodley at 5:24 PM on October 3, 2013 [9 favorites]


The almond is in the pool noodle. Pass it on.
posted by Ardiril at 5:29 PM on October 3, 2013


"17 teaspoons is about 84 ml" - 84 ml is still a helluva lot of sugar.
posted by Ardiril at 5:49 PM on October 3, 2013


You and I are complicated, but we're made of Elements.
posted by buriednexttoyou at 5:56 PM on October 3, 2013


How is babby formed?

This meme always pissed me right the hell off. Someone has curiosity about how the world works - someone who maybe isn't as educated or articulate in the written word as they'd like to be - and they are mocked cruelly by basically the entire internet for the crime of trying to learn something new.


It's just a synedoche, we are mocking "They need to do way instain mother" being the Best Answer! Chosen by Voters! and the general uselessness of Yahoo Answers.
posted by Tom-B at 6:42 PM on October 3, 2013 [1 favorite]


The amount of mass converted is tiny, but definitely not zero-- E=mc2, remember.

There are exactly 0 atoms, electrons, protons, neutrons or anything else that you'd consider to be matter converted into energy in this process.
posted by empath at 9:30 PM on October 3, 2013 [2 favorites]


There are exactly 0 atoms, electrons, protons, neutrons or anything else that you'd consider to be matter converted into energy in this process.

Almost exactly. Atoms are a bit fuzzy around the edges.

Fat is definitely matter, as are water and carbon dioxide. The smallest unit of any of these substances is a molecule. The mass of a molecule is equal to the sum of the masses of the constituent atoms, plus a tiny correction term to account for the m=E/c2 mass equivalence of the bond (chemical) energy involved in molecule formation.

If the molecule formation process is endothermic (heat-consuming) then that correction term will be positive: the molecule's mass will be higher than that of its constituent atoms. If forming the molecule is exothermic (heat-releasing) the correction term will be negative. It is many orders of magnitude smaller than the atomic masses, making it almost always negligible, but it's there.

The process of converting fat molecules to water and carbon dioxide molecules is exothermic, meaning that the resulting water and carbon dioxide will indeed have very very very very very very very slightly less mass than the fat burned to form them.
posted by flabdablet at 4:29 AM on October 4, 2013 [1 favorite]


As for this guy bemoaning his failure to find a basic understanding of chemistry among the good citizens of Bondi: I would bemoan that too, were I not already busy bemoaning the proportion of people unable to give me correct answers when asked (a) how long it takes the Earth to make a single revolution on its own axis (b) how long it takes the Earth to complete a single orbit around the Sun.
posted by flabdablet at 4:39 AM on October 4, 2013


The almond is in the pool noodle. Pass it on.

Isn't that the plot of The Human Centipede?
posted by flabdablet at 4:42 AM on October 4, 2013 [1 favorite]


The process of converting fat molecules to water and carbon dioxide molecules is exothermic, meaning that the resulting water and carbon dioxide will indeed have very very very very very very very slightly less mass than the fat burned to form them.

There is a difference between mass and matter and I think maybe that is where some of the confusion is coming from. There is no matter being converted into energy here. Not almost none. None.
posted by empath at 4:53 AM on October 4, 2013


There is a difference between mass and matter

Mass is the measure of matter. If you create energy by reducing a mass, you have converted matter into energy -- that is the precise meaning of E = mc2.
posted by localroger at 5:11 AM on October 4, 2013


If you throw a ball, you've increased its mass, by imparting kinetic energy to it. You haven't created any new matter, though.
posted by empath at 6:00 AM on October 4, 2013


If you create energy by reducing a mass, you have converted matter into energy -- that is the precise meaning of E = mc2.

Also, the energy isn't 'created', it's released. The energy released in an exothermic reaction was already there in the chemical potential of the molecule. It wasn't stored as matter.
posted by empath at 6:02 AM on October 4, 2013


Isn't that the plot of The Human Centipede?

You know what bothers me? There are four legs per segment -two human arms and two human legs - so taxonomically speaking it is clearly not a human 'centipede', but a human millipede. I wrote a strongly worded letter to the director asking him to explain this egregious oversight and am currently awaiting his response.
posted by Literaryhero at 6:13 AM on October 4, 2013 [5 favorites]


The energy released in an exothermic reaction was already there in the chemical potential of the molecule. It wasn't stored as matter.

Mass-energy is always either mass or energy, and if it's not being energy (e.g. it's "stored") it's being mass. There is no third option. If you had a precise enough scale (which you don't) you would see that the molecule with the energy stored in its bond is very slightly heavier than the individual atoms.

This is, incidentally, exactly the same thing that happens in nuclear reactions and you could make exactly the same argument (being exactly as wrong) that "matter" isn't being consumed because the number subatomic particles in the collected nuclei does not change. However, their mass does change -- in this case by a more observable amount -- when they are bound together. This is the reason for all those decimal points in the mass figures on the Periodic Table.
posted by localroger at 8:10 AM on October 4, 2013 [1 favorite]


Um... no.

The main reason for all those decimal points in the mass figures on the Periodic Table is because those figures are weighted averages of the atomic masses for a mixture of isotopes.
posted by flabdablet at 9:02 AM on October 4, 2013


There is a difference between mass and matter

In what units do you measure matter?
posted by flabdablet at 9:03 AM on October 4, 2013


flabdablet, those decimal points are still there in tables that break out the isotopes. He4 weighs about 99.5% of what two Dt's weigh, and the difference is what powers hydrogen bombs. The most egregious exception, and the first noted, to the integer simplicity of the Periodic Table is Hydrogen, because having no nuclear bonds at all it is very noticeably heavier than it should be compared to all other elements.

Chemical bonds aren't magically different than atomic bonds, but the mass equivalence is much harder to measure. It is, however, still there; the math offers no alternative.
posted by localroger at 9:34 AM on October 4, 2013


those decimal points are still there in tables that break out the isotopes.

Break out the isotopes? What wild suggestion is this?

It could lead to dancing!
posted by flabdablet at 9:39 AM on October 4, 2013 [1 favorite]


I think there is some terminology confusion that is causing some apparent disagreements where there isn't really any.

First off, E = mc^2 isn't the full equation, the full equation is E^2 = m^2c^4 + p^2c^2 (source: http://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation ). The p stands for momentum.

This means that the energy of a system (such as a human body, or a single chemical reaction) is related to the rest mass of the system plus the momentum of the system for a given reference frame.

Mass and rest mass are NOT the same thing. This is a crucial point. This is also related to how photons (light particles) can impart energy even though they have no rest mass - it's because they have momentum. (more here: http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html)

Matter in the context of chemical reactions is generally a reference to the constituent components of atoms, i.e. electrons, protons, and neutrons. However, the mass of an atom is not just the rest masses of these particles, it also contains the nuclear binding energy that holds the nucleus together, the electron binding energy that keeps the electrons bound to the nucleus, and the momentum of the atom.

A simple example of the atom having momentum even when it's part of a system at rest compared to us, is when the system has heat. The heat is manifest as atoms jiggling about relative to each other, hence moving.

If you have a molecule, you also have binding energy keeping the molecule together, which increases the mass of the molecule over and above the weight of the individual atoms alone.

This is a second crucial point. Matter has mass, but things that are not matter can also have mass, including various forms of potential energy, photons (which have 0 rest mass), etc.

In ordinary exothermic reactions, like those that 'burn' fat and produce CO2, etc. the reactions involve turning some of this molecular binding energy into heat. The end products of the reaction have binding energies that are less than that of the binding energy of the beginning molecule(s), with the different precisely that of the added momentum of the end products in the form of heat.

In fact, if you were to measure the mass of the beginning molecules right before the reaction and that of the end products right after the reaction you would find they are identical (handwaving a little here, in reality the reactions aren't happening in a vacuum, so there are other inputs and outputs from the other particles around the reaction, but for these purposes we'll pretend the chemical reaction is a closed system).

However, the heat would soon dissipate, taking some of the momentum away from the system. Then and only then would the mass be reduced as the heat was lost (i.e. the momentum transferred outside the system).

So we end up with a reaction where energy changes forms, and some is transferred out of the system, thus lowering it's mass. But the amount of 'matter' (atomic matter) is unchanged.
posted by 1024x768 at 9:39 AM on October 4, 2013 [4 favorites]


That's why I asked empath to specify the units he's measuring "matter" in.

As you note, when discussing chemical reactions it's reasonable to talk about quantities of matter by playing count-the-particles, and since chemical reactions don't destroy nuclei or electrons but merely shuffle them about, they don't alter quantities of matter specified in this way.

But the larger discussion here is about the conversion of body fat to carbon dioxide and water, and the ways in which the body loses mass when that happens. Body mass is measured in kilograms, not in particle counts, and when the carbon dioxide is exhaled and the water excreted it's at body temperature, same as the fat that's left behind; the reaction heat has already left the reaction sites, so the matter leaving the body really does have ever so slightly less mass than it did while it was still in the form of body fat.
posted by flabdablet at 9:56 AM on October 4, 2013


Flabdablet: We are in agreement, as long as we specify one technicality - the word 'matter' here refers to the molecules along with their energy state (e.g. binding energy, current configuration as molecules, etc.). The Fatty acids in the stored fat have more potential energy in their bonds than the carbon dioxide and water do, the difference was released as heat.

The mass difference is a consequence of the difference in molecular binding energy between the fatty acids consumed and the CO2 and H2O released.
posted by 1024x768 at 10:22 AM on October 4, 2013 [1 favorite]


"waste chemicals in your urine" - This is the one that was throwing me off. However, a very quick google search indicates that urea is two parts ammonia to one part carbon dioxide.

The balance between exhaled carbon dioxide and urea requires more digging than I care to do.
posted by Ardiril at 12:40 PM on October 4, 2013


Yes I am talking about matter in the counting particles sense.
posted by empath at 12:51 PM on October 4, 2013


While the accuracy is questionable, I think we can take the .04% CO2 inhaled versus the 4% CO2 exhaled figures as decent ballpark figures, meaning, inhaled CO2 is insignificant.

http://www.biotopics.co.uk/humans/inhaledexhaled.html
posted by Ardiril at 1:27 PM on October 4, 2013


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