The Naked Scientists

The Naked Scientists Forum

Author Topic: Why does detergent heat while it dissolves?  (Read 1933 times)

Miguel Navarro

  • Guest
Why does detergent heat while it dissolves?
« on: 25/05/2008 09:45:16 »
Miguel Navarro  asked the Naked Scientists:

Hello there!! Hi Chris and everyone at The Naked Scientists!
 
This is just to tell you how wonderful and informative your podcast is and to let you know that you have many fans here in Mexico and the rest of Latin America and I'm one of them.
 
Just a quick question for you. I don't now if you have noticed that when you take a handful of detergent and dip it into water it sort of heats while it dissolves. I think this has something to do with friction but I'm not sure. Could you please tell me why this happens??
 
Thank you very much!!
 
Miguel Navarro Gamboa
Puerto Vallarta Jalisco, Mex.

What do you think?


 

Offline Andrew K Fletcher

  • Neilep Level Member
  • ******
  • Posts: 2331
  • KIS Keep It Simple
    • View Profile
Why does detergent heat while it dissolves?
« Reply #1 on: 25/05/2008 09:54:51 »
Hello Miguel and welcome to Nakedscientists. I have not heard of detergent heating the fluid it dissolves in. The friction theory for this is interesting to me and hopefully someone will enlighten us as to how or why this should be.

Andrew
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8669
  • Thanked: 42 times
    • View Profile
Why does detergent heat while it dissolves?
« Reply #2 on: 25/05/2008 17:48:34 »
I haven't met a detergent that does this, but plenty of chemicals dissolve in water with the relearse of heat. The requiremnt is that the hydration energy excedes the lattice energy. Since a lot of detergents are composed of pairs of large and small ions the lattice energy will generally be quite low, if the hydration energy of the small ion is large (and that's not unreasoanble on electrostatic grounds) the dissolution will be exothermic.
In short, if the sodium ions are happier in solution than in the detergent crystals, then the stuff will get warm as it dissolves.
 

The Naked Scientists Forum

Why does detergent heat while it dissolves?
« Reply #2 on: 25/05/2008 17:48:34 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums