What happens to molecules as an object stretches?

[CuriousBanker]

Let's say you have an object, such as a shirt, and you pull it in all directions. After a while it will become permanently stretched out. This is obvious on an every day level. But what is happening molecularly? Are the molecules becoming pushed further and further apart from each other? If so, how are they still attracted to each other enough to stay bonded?

[Iota]

Let's say you have an object, such as a shirt, and you pull it in all directions. After a while it will become permanently stretched out. This is obvious on an every day level. But what is happening molecularly? Are the molecules becoming pushed further and further apart from each other? If so, how are they still attracted to each other enough to stay bonded?

 

The molecules don't change. The fibres move positions in the object.

[CuriousBanker]

I don't understand. Aren't the fibers made of molecules like everything else?

[Iota]

I don't understand. Aren't the fibers made of molecules like everything else?

 

Indeed, they are. But there are many folds in the fibres- before you even reach the molecular level. Stretching the object only causes the 'macro folds' to become unfolded. (macro fold isn't real terminology, I'm using it to help though.)

 

In the picture I've attached, you can see the 'primary folding' (the big zig-zag). If we magnify a section of the primary folding [in green], we find there is a secondary folding within it. This can repeat many, many times. But so what?

 

When you stretch, say, a shirt. It is impossible to unfold all of the foldings, let alone therefore, to reach/affect the molecular level, which is smaller than all of the folds before it.

 

This prevents tension reaching the molecular level.

 

 

Did this explanation help?

[CuriousBanker]

Kind of. But I am still a little confused. If the macro changes, the micro has to change to. If all of the molecules stayed exactly the same, then the macro could not change...right? How could a bigger picture change without the smaller picture underlying it also change if the bigger picture is made up of the smaller pictures?

[Iota]

Kind of. But I am still a little confused. If the macro changes, the micro has to change to. If all of the molecules stayed exactly the same, then the macro could not change...right? How could a bigger picture change without the smaller picture underlying it also change if the bigger picture is made up of the smaller pictures?

 

 

What I said wasn't strictly true, in that, the molecules are affected. In a sense. Their positions in space change when you stretch the shirt, but the molecules' connections to each other are unchanged... that is, the bonds aren't pulled apart, and the molecules are all the same positions relative to each other.

 

I think at this point you need to learn more about the atomic level and how it results in the macro-level structures. Otherwise you will struggle to understand it. I can see the gap in your understanding, and it's not easy to fill without teaching you a fair amount of chemistry with detailed examples.

 

 

 

 

 

 

[CuriousBanker]

Would an into to chemistry textbook suffice?

[Iota]

Just this free website should do the trick: http://www.chemguide.co.uk/

 

There's a section called atomic structures and bonding.

 

I can't really recommend any reading for chemistry, unless you want to buy OCR AS chemistry. Because that's basically where I learnt all of the fundamentals up to this point; along with the A2 book.

 

Edit: Look into DNA. See its primary, secondary, tertiary and quaternary structure when making up protein. This should help you too.

Edited August 19, 2012 by Iota