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Why do objects stay together?

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exfret
#1
Jun19-13, 08:27 PM
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I thought this when I was pondering how, when you sit on a chair, you're butt isn't really touching the chair; it's just interacting at short distances with its electrons. After thinking about that, I realized that your torso isn't touching your butt either, it's just interacting at short distances with its electrons as well. So, if your torso and your butt are pretty much as connected to each other as your butt and the chair, then why is it that when you stand up from sitting in the chair, your butt comes with you, but the chair doesn't? I understand that metallic bonds hold together metals sometimes, but those can't possible hold together your whole body, right, or can metallic bonds operate on large chunks of nonmetals and what-not mixed together as well? Also, if something like metallic bonds do hold together your body, then why wouldn't they attach you to the chair once you sat on it?
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Drakkith
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Jun19-13, 09:12 PM
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Here are the different types of bonds and a little of how they work: http://en.wikipedia.org/wiki/Chemical_bond
SteamKing
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Jun19-13, 11:42 PM
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If my torso was touching my butt, I would be shaped like a pretzel. What is this fixation you have with things touching your butt?

exfret
#4
Jun20-13, 01:10 PM
P: 16
Why do objects stay together?

Quote Quote by Drakkith View Post
Here are the different types of bonds and a little of how they work: http://en.wikipedia.org/wiki/Chemical_bond
I was kind of hoping that someone wouldn't just give me a link to a huge page on Wikipedia and say, "Here, the answer to your question is probably somewhere inside." I'm not lazy, but I'm not going to waste my time reading over a whole Wikipedia page that may not even contain the answer to my question. If I wanted a Wikipedia page, I would have brought one up myself. Is there a specific part of that page that you think will answer my question? If you find a web page that you think is interesting and that relates to my question, then I would gladly read it as long as you include a reference to the exact part of the page that relates to my question. Do you have something useful to share, like any knowledge about the different types of bonds and/or how they might relate to sitting in a chair? If you do, then it would be great if you could share that knowledge with me, because I am very curious about this chair thing.

Quote Quote by SteamKing View Post
If my torso was touching my butt, I would be shaped like a pretzel. What is this fixation you have with things touching your butt?
Okay, fine, maybe I should have said that your waist touches your butt, but that isn't the point of my asking this question (and besides, your butt technically doesn't touch anything either; it's just interacting at short distances with other things' electrons). I am genuinely puzzled. It would be helpful if you could reply to my post with some information that could help me better understand what is happening when you sit down and sit up. After all, that is what this thread is all about.

Also, neither of these posts have even partly answered my question. I would very much appreciate it if someone who knew the answer to my question would post it.
Drakkith
#5
Jun20-13, 04:40 PM
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Okay, fine, maybe I should have said that your waist touches your butt, but that isn't the point of my asking this question (and besides, your butt technically doesn't touch anything either; it's just interacting at short distances with other things' electrons).
Ah, but that IS touching! I suppose the answer to your original question is that your butt doesn't stick to the chair because the atoms and molecules interact but do not form chemical bonds. Without bonding two atoms do not stick together.
exfret
#6
Jun20-13, 07:12 PM
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Quote Quote by Drakkith View Post
Ah, but that IS touching!
Technically speaking, no. Touching is when two objects are so close together that there isn't any space in between them. I guess it does actually depend on the way you define "touching," in which case, I have no right to say your wrong, but you have no right to say I'm wrong either.

Quote Quote by Drakkith View Post
because the atoms and molecules interact but do not form chemical bonds. Without bonding two atoms do not stick together.
So every single atom in your body is chemically bonded? What about when the chair turns out to be a butt-eating chair and it eats off my butt. Does that break the chemical bonds between my torso waist and my butt? I thought that cutting/biting off was a physical change, but wouldn't it have to be a chemical change if it involves breaking the chemical bonds between my butt and my waist?
Integral
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Jun20-13, 07:53 PM
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Boundary layers, that is what separates different bodies. Generally (on metals) a layer of oxide forms which protect the bulk of metal from further reaction. Undoubtedly similar layer exist on non metals.
Drakkith
#8
Jun20-13, 08:04 PM
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Quote Quote by exfret View Post
Technically speaking, no. Touching is when two objects are so close together that there isn't any space in between them. I guess it does actually depend on the way you define "touching," in which case, I have no right to say your wrong, but you have no right to say I'm wrong either.
Technically speaking, yes, it is. There is no other form of 'touching'. Things do not get so close that there is no space between them. Even defining something like the size and boundaries of an atom is problematic since it relies on a probability map of where the electrons might be at any given time.

So every single atom in your body is chemically bonded?
Practically all of them. I'm sure there are a few floating around that aren't bonded. Keep in mind that your body is a complex object made up of trillions upon trillions up cells, all surrounded by a network of connective tissue and fluids, in which trillions of other things like bacteria and viruses stroll through like they own the place. In such an environment I doubt there are any quick, simple answers.

What about when the chair turns out to be a butt-eating chair and it eats off my butt. Does that break the chemical bonds between my torso waist and my butt?
The simple answer is yes. However you'd have to look into everything that actually holds your body together and see how it all works to get a full understanding. Your body isn't a solid object with only one type of bond between everything. It has many different ways of staying intact and all operate differently. My knowledge on the subject is very limited, so I can't give a 100% definitive answer.

I thought that cutting/biting off was a physical change, but wouldn't it have to be a chemical change if it involves breaking the chemical bonds between my butt and my waist?
I'm not sure what the distinction is between 'physical change' and 'chemical change' is in this circumstance.
Simon Bridge
#9
Jun20-13, 09:03 PM
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The questions seem to have started with how things stay together to how they stay apart.
It's quite a big subject and a lot of the answers are more about exploring what is meant when we say that two bits are part of the same object ... what do we mean when we say that two things are touching - and so on. A lot of confusion comes from being imprecise about these things - but being precise will make for too much writing. So what we do is provide a bunch of rules for which there will be some exceptions.

Very generally, seperateness and togetherness are emergent properties of underlying electromagnetic interactions.
There is a sense in which we can say that nothing is really separate from anything else ... being careful about the definition of "really". But there is also a more immediate sense in which I like to think the table I'm sitting at is not part of me and the table owner encourages this way of thinking. A lot of this thread, therefore, is in the context of this way of thinking.


We can do a lot by thinking of the common understandings and investigating what happens. i.e. a smooth surface that we see is the strong scattering region for the ambient light averaged over many detection events in our eyes and processed in the visual cortex before becoming part of our conscious awareness ... the link between physics, biology, chemistry, and consciousness being an, as yet, unsolved problem.

When we say two objects are touching, then actually measure the gap very accurately, we will discover that it is not zero ... it's just small enough for the description "touching" to make sense... usually that means the gap is too small to see with the eye, or by some, otherwise useful, measuring process.


The old saw is about why one object does not pass through another ... both are made of atoms, and are mostly empty space (it goes) and there is plenty of room for the atoms to pass each other, so why can't you push your hand through the table or walk through walls?

Practically all the things we think of, in every day terms, as surface properties are about electrons ... objects like your hand and the table stay separate in normal circumstances because the electrons of your hand repel the electrons in the table ... the repulsion increases as they get closer and, classically, it gets infinite for zero separation: so there is no way you can exert enough force with just your muscles to push your hand through the table.

Something like a biological organism is basically a complicated bag of stuff, with bits and bobs all tangled up.
Every atom in your body is chemically bonded to some other atom in your body ... but not all the molecules are chemically bonded to each other, there are cells floating in fluid in your veins and arteries for example. When you get beyond chemistry it's more about which bag the stuff is in or how the fibers are wrapped around each other.

Bags contain stuff for the same reason you cannot push your hand through the table.

Some stuff is stickier than others - look up the origin of friction and adhesion: it's a whole field of study by itself - but it boils down to how the electrons are arranged close to the classical surface of the stuff. The stickiness is how fibers can get wrapped around each other without having zero separation between any of their parts.

When the killer chair eats your butt, it does not have to break chemical bonds - it just has to tear the fibers apart.
In general, this may involve breaking weak bonds and adhesion and so on just because bodies are very complicated.

And so on and on - it is a very big subject.
For more in-depth you should be reading about the theory of complex systems (chaos math for example - and cellular automata).
In these forums we can handle simpler systems like two blocks of metal being rubbed together - makes for less typing ;)
Drakkith
#10
Jun21-13, 12:03 AM
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Thanks Simon, that is exactly what I wanted to say but couldn't explain.
exfret
#11
Jun21-13, 09:22 AM
P: 16
Hmm. So what about the chair? Is the wood of my chair bonded? (Really it's not a wooden chair, but it isn't a man-eating chair either). Are so many everyday objects bonded so that when they are pushed down by gravity, they don't act like a liquid and 'melt' to the floor? Why do solids retain their shape? Does every solid have a chemical bond running through itself? So, does this mean that there is a special 'solid bond' that bonds all solids together? Or is it just friction somehow acting on atoms? How would friction act on atoms? I just can't imagine a molecule or an atom acting as something other than an individual particle unless it has some special type of chemical bond to 'stick' it to something else.
nasu
#12
Jun21-13, 10:00 AM
P: 1,969
Quote Quote by exfret View Post
Why do solids retain their shape? Does every solid have a chemical bond running through itself? So, does this mean that there is a special 'solid bond' that bonds all solids together? Or is it just friction somehow acting on atoms? How would friction act on atoms? I just can't imagine a molecule or an atom acting as something other than an individual particle unless it has some special type of chemical bond to 'stick' it to something else.
There different types of solids, in terms of forces that keep them together.
Some are similar to chemical bonds (like the covalent crystal of diamond) other are more specific to solids (like the "metallic" bond in metals).
There are also ionic crystals where the ions are held together by electrostatic forces and van der Waals crystal with very week electric dipole forces.

I don't think that the distinction between "chemical" bonds and other types of bonds is really relevant for your question.
Drakkith
#13
Jun21-13, 03:36 PM
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Quote Quote by exfret View Post
Hmm. So what about the chair? Is the wood of my chair bonded? (Really it's not a wooden chair, but it isn't a man-eating chair either).
Of course. Similar to our body, there are many different types of mechanisms that give wood its strength and allow it to hold its shape. Yet all rely on different types of bonds between atoms at the very basic level.

Are so many everyday objects bonded so that when they are pushed down by gravity, they don't act like a liquid and 'melt' to the floor?
Yes. However I think it's important to understand that atoms/molecules in a liquid typically have weak bonds between themselves too. A perfect example is water. A water molecule consists of one oxygen and two hydrogen atoms bound in such a way that makes the entire molecule polar, meaning that one side is positively charged and the other side is negatively charged. This allows water molecules to have weak bonds between their positive and negative sides and is the reason water is a liquid as such a high temperature compared to many other types of compounds. If it did not have these bonds water would melt and boil at much lower temperatures than it currently does.

Why do solids retain their shape? Does every solid have a chemical bond running through itself? So, does this mean that there is a special 'solid bond' that bonds all solids together?
Some solids, such as metals and crystals, have a single type of bond between their atoms, but most have a mix of different types of bonds. This is especially true of complex objects such as wood, the human body, and your chair as a whole.
See this article for more: http://en.wikipedia.org/wiki/Bonding_in_solids

Or is it just friction somehow acting on atoms? How would friction act on atoms?
No, it's not friction. Friction is different. It is the force that resists relative motion between two objects. It would be better to make a new thread if you want to understand what friction is.

I just can't imagine a molecule or an atom acting as something other than an individual particle unless it has some special type of chemical bond to 'stick' it to something else.
You are correct. Without a bond, an atom does not act like anything else but a single atom. For example, a helium atom is very very stable and will not bond with anything else under normal circumstances. Because of this, helium does not form molecules and never partakes in chemical reactions. It is always a monatomic gas, meaning it is always found as single atoms in a gaseous state except under the most extreme of circumstances.
exfret
#14
Jun21-13, 04:07 PM
P: 16
Okay, I understand now. I thought that there would be some reason why objects stayed together that had nothing to do with chemical bonding. I hadn't realized that chemical bonding was so widespread. Just imagine, the atoms in every human are bonded (well, maybe not every atom, but most of them), especially those of Double 'O' Seven.
Drakkith
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Jun21-13, 04:26 PM
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Quote Quote by exfret View Post
I hadn't realized that chemical bonding was so widespread. Just imagine, the atoms in every human are bonded (well, maybe not every atom, but most of them), especially those of Double 'O' Seven.
*groans*
pongo38
#16
Jun21-13, 05:44 PM
P: 696
I appreciate what has been said in this thread, but would like to add that a glue manufacturer told me that we don't really need glue to bond two flat surfaces together if the mating surfaces are perfectly flat (But in reality, we don't achieve that, usually)
Simon Bridge
#17
Jun21-13, 05:44 PM
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Quote Quote by exfret View Post
Hmm. So what about the chair? Is the wood of my chair bonded? (Really it's not a wooden chair, but it isn't a man-eating chair either). Are so many everyday objects bonded so that when they are pushed down by gravity, they don't act like a liquid and 'melt' to the floor? Why do solids retain their shape? Does every solid have a chemical bond running through itself? So, does this mean that there is a special 'solid bond' that bonds all solids together? Or is it just friction somehow acting on atoms? How would friction act on atoms? I just can't imagine a molecule or an atom acting as something other than an individual particle unless it has some special type of chemical bond to 'stick' it to something else.
Did you read my last response?
See if you can attempt an answer to your own question in those terms ... that way I can tell what you are learning and how you are thinking, and I can adjust the form of the answers to suit.

Right now it just looks like you are throwing out random questions without regard to the answers you have received so far. It can be fun just throwing questions out and getting some answers back - but the idea of these forums is to learn to find your own answers.

i.e. you have already, repeatedly, been told about the different ways that solid objects can become solid. You appear to be stuck on the idea of being "bonded" somehow, but don't seem to notice the different ways of being "bound". Did you attempt to look up the things I suggested? What did you find out?
Swegner99
#18
Jun21-13, 06:02 PM
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Quote Quote by pongo38 View Post
I appreciate what has been said in this thread, but would like to add that a glue manufacturer told me that we don't really need glue to bond two flat surfaces together if the mating surfaces are perfectly flat (But in reality, we don't achieve that, usually)
How does that work?


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