Answer: London dispersion forces (i.e LDF), also known loosely Van dear Waals forces.
Explanation: The London dispersion forces is named after the German - American physicist called Fritz London.
The London dispersion forces describes the interaction between two atoms A and B after London discovered the "quantum mechanical theory".
London dispersion theory is similar to the quantum mechanical theory of "light dispersion", that is why it is called "dispersion effect". In Physics,dispersion can be explained as the variation of a quantity with frequency, which is the fluctuation of the electrons in the case of the London dispersion.
The molecules which evaporate presumably take heat away from the liquid. So, I'd disagree with the classmate. Whether the amount of cooling would differ from the usual case wherein the molecules have different speeds is another question.
I guess the argument goes something along the lines of that the faster moving and therefore most kinetically energetic molecues evaporate and take away most heat. But if there's no faster moving molecules, 'cos they all have the same speed well, then presumably they'd all take away the same amount of heat. So, maybe the cooling would be less. No cooling though ??? Hmmmm dunno .... i think not ....
Potential energy increases as speed decreases. Kinetic increases when speed increases.