Wikipedia:Sandbox/Archive

 The phrase microwave effect is a term that is actually applied to a range of observations in microwave chemistry.
 There are two general forms of microwave effect 
  
 * Microwave-specific effects
 * Non-thermal microwave effects

 Microwave-specific effects are those effects that cannot be (easily) emulated 

through conventional heating methods. Examples include; selective heating of particular reaction components, large heating rates and temperature gradients and superheating of solvents. Microwave-specific effects tend not to be controversial and invoke "conventional" explanations for the observed effects.

  Non-thermal effects have been posited in order to explain unusual observations in microwave chemistry.  As the name suggests, the effects are supposed not to require the transfer of microwave energy into thermal energy.  Instead, the microwave energy itself directly couples to energy modes within the molecule or lattice.  Non-thermal effects in liquids are almost certainly non-existent, as the time for energy redistribution between molecules in a liquid is much less than the period of a microwave oscillation.  Effects in solids are still part of an ongoing debate.  It is likely that microwaves cause plasma formation and enhance diffusediffusion in solids via second-order effects, and so may enhance sintering processes.  Debates are currently raging (January 2006) about non-thermal effects of microwaves during solid-state phase transitions.         

References

• ^[1] Microwaves in organic synthesis. Thermal and non-thermal microwave effects, Antonio de la Hoz, Angel Diaz-Ortiz, Andres Moreno, Chem. Soc. Rev., 2005, 164-178