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?