alpha2cen Posted December 19, 2010 Share Posted December 19, 2010 Everyone knows well high temperature copper is bigger than colder one. We know this macroscopical phenomena very well. And there is a parameter related to this phenomena such as thermal expansion factor. But we don't know well about it at the molecular level. Why copper is expanded when temperature is increased ? Link to comment Share on other sites More sharing options...
John Cuthber Posted December 19, 2010 Share Posted December 19, 2010 "But we don't know well about it at the molecular level." Yes we do. The simple answer is that at higher temperatures the electrons have more energy. So they can occupy energy levels further away from the nucleus. That makes the atoms in the copper slightly bigger. Since the number of atoms in the copper bar is the same and the atoms get bigger the bar gets bigger. Link to comment Share on other sites More sharing options...
swansont Posted December 19, 2010 Share Posted December 19, 2010 Atoms in a lattice are similar to masses connected by springs. When you shake them (i.e. they get hotter), the amplitude of the vibration is larger. The whole ensemble gets bigger. Link to comment Share on other sites More sharing options...
confidenceguy Posted December 19, 2010 Share Posted December 19, 2010 you can also find more details about it on http://en.wikipedia.org/wiki/Soldering Link to comment Share on other sites More sharing options...
alpha2cen Posted December 20, 2010 Author Share Posted December 20, 2010 Are there any possibility about molecular attraction force is reduced? There are many reason to be done like this. Is the vibration important role on the solid state energy storage at high temperature? Which percentage does the vibration energy contribute to? Link to comment Share on other sites More sharing options...
John Cuthber Posted December 20, 2010 Share Posted December 20, 2010 "Are there any possibility about molecular attraction force is reduced?" Yes, that's why blacksmiths heat iron bars before hammering them into shape. "Is the vibration important role on the solid state energy storage at high temperature?" Yes "Which percentage does the vibration energy contribute to? " It depends on the system and the maths is pretty horrible. http://en.wikipedia.org/wiki/Debye_model Link to comment Share on other sites More sharing options...
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