Lack of quantum effects at higher temperatures

[trelek2]

I readhttp://www.learner.org/courses/physics/unit/text.html?unit=6&secNum=6" article and started wondering: What is the real reason for classical behavior of liquids gases at room temp?

I have always thought that it is because of the deBroigle wavelength relation. At room T particles have a high momentum and so their wavelengths are very small in comparison with separation between atoms of the fluid. Therefore we don't have quantum interference and no quantum effects?

But in the article (the very last 2 paragraphs) they seem to be saying that the quantum effects vanish because particle wavelengths are out of phase with one another.

Which version of the story is true? Or which truth is more veracious?

 

[Drakkith]

What they are saying is that as you heat up and oscillating BEC the oscillations begin to dampen out because the heat causes the particles to interfere with each other instead of reinforce the oscillations. This is only occurring at very very low temperatures, far from room temperature. Both effects you list do happen, but the phase of the wavelengths only matters at extremely low temperatures.