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Thread: Stuck for an answer to a kid's question.

  1. #1 Stuck for an answer to a kid's question. 
    Forum Cosmic Wizard
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    Why is some stuff more sticky than other stuff?


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    Bullshit Intolerant PhDemon's Avatar
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    In glues there is often a chemical reaction between the surfaces (usually a polymerisation reaction between the molecules in the glue and the molecules in the surface, the chemistry dictates the stickiness. For things that aren't glues it is basically down to hydrogen bonds or van der Waals forces between the surfaces. Different "stuff" has differing strength hydrogen bonds / van der Waals interactions between it and what it is sticking to...


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    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by dan hunter View Post
    Why is some stuff more sticky than other stuff?
    Because some stuff is sticky and other stuff isn't.
    Therefore, by default, some stuff is stickier than other stuff.
    Sticky is stickier than not sticky.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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    Forum Professor Daecon's Avatar
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    It also depends on what the stuff is trying to stick to. One half of velcro is very sticky to the other half, but not much else.
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    Bullshit Intolerant PhDemon's Avatar
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    That's a design thing (physical hooks on one bit, things that like to be hooked on another) rather than a chemical/basic physics thing though isn't it?
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    Forum Professor Daecon's Avatar
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    Quote Originally Posted by PhDemon View Post
    That's a design thing (physical hooks on one bit, things that like to be hooked on another) rather than a chemical/basic physics thing though isn't it?
    That's true, of course.

    What's the age of the person asking the question? Would they regard the distinction as important?

    You could also mention things like the feet of a gecko, too. I'm sure they're "more" sticky depending on the surface that the gecko is walking on.

    Unless of course they're talking about stuff like post-it notes and superglue.
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    Forum Professor scoobydoo1's Avatar
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    Quote Originally Posted by PhDemon View Post
    In glues there is often a chemical reaction between the surfaces (usually a polymerisation reaction between the molecules in the glue and the molecules in the surface, the chemistry dictates the stickiness. For things that aren't glues it is basically down to hydrogen bonds or van der Waals forces between the surfaces. Different "stuff" has differing strength hydrogen bonds / van der Waals interactions between it and what it is sticking to...
    I've done some minor reading into the mechanism for adhesiveness when making molds and casting pieces of work many years ago, and I've always wondered whether this applies to viscosity as well? Any thoughts?
    Last edited by scoobydoo1; May 27th, 2014 at 11:38 AM.
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    Bullshit Intolerant PhDemon's Avatar
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    I could be wrong but to my mind viscosity is more about the forces between the molecules in the stuff which restricts it flowing rather than between the stuff and a surface...
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    Forum Cosmic Wizard
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    Quote Originally Posted by Daecon View Post
    What's the age of the person asking the question? Would they regard the distinction as important?

    You could also mention things like the feet of a gecko, too. I'm sure they're "more" sticky depending on the surface that the gecko is walking on.

    Unless of course they're talking about stuff like post-it notes and superglue.

    It is the neighbour's kid and I think she is 9 or 10. She meant pricing label gum and contact cement.
    It was when I tried explaining how contact cements work that I realized I didn't have a good clear answer she could understand easily.
    Then I realized I didn't have a good clear answer that I could understand easily either.
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