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Temperature and Free Energy

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Kelvin 506
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­­­­­­Kelvin 506

Credit: James Lee
Source: http://www.flickr.com/photos/jronaldlee/6319849827/
License: CC BY-NC 3.0

I would guess you’ve never read a book by the title of “Kelvin 506”. Interestingly, it has been proposed that this is the temperature at which paper experiences auto-ignition – it spontaneously combusts!

Why It Matters

  • The temperature matters a lot for some reactions (Have you ever tried to cook an egg at room temperature?). When the products of a reaction are not favored or when a reaction cannot occur, the reaction is deemed non-spontaneous. Changing the temperature can render processes spontaneous (note: this does not always mean you should increase the temperature; some processes are only spontaneous at lower temperature – think freezing water.)
  • Credit: Andrew Malone
    Source: http://www.flickr.com/photos/andrewmalone/944345776/
    License: CC BY-NC 3.0

    Frying an egg requires the constant application of heat to the pan. Simply raising the temperature of the pan to a specific temperature will not work. The egg will start frying, and quickly stop when the temperature drops [Figure2]

     

  • For more on this, watch the following video: 

https://www.youtube.com/watch?v=Fnkv7iMHq_w

Can You Apply It?

With the links below, learn more about how temperature affects the spontaneity of a reaction. Then answer the following questions.

  1. The sign of \triangle G (positive or negative) determines if a reaction is spontaneous or non-spontaneous. Since\triangle G=\triangle H-T(\triangle S) it is possible for \triangle G to be negative at all possible temperatures. When is this the case?
  2. Not all paper auto-ignites at 506 K. Please provide some reasons that this might be the case.

Image Attributions

  1. [1]^ Credit: James Lee; Source: http://www.flickr.com/photos/jronaldlee/6319849827/; License: CC BY-NC 3.0
  2. [2]^ Credit: Andrew Malone; Source: http://www.flickr.com/photos/andrewmalone/944345776/; License: CC BY-NC 3.0

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