Anomalien der Zutat "Wasser"

Man glaubt ja, "Wasser" sei etwas Gewoehnliches und Altbekanntes -- dabei hat es aus chemischer Sicht eine Menge Ueberraschungen auf Lager.

Eine (engl.) Webseite mit Erklaerungen, z.B.:

"41 Warm water vibrates longer than cold water

It is expected that the lifetime of an excited molecular vibration should decrease as the temperature increases as the energy and likelihood of interactions with other molecules also increase. For example, the lifetime of the excited liquid HCl stretch vibration decreases from 2.1 ns at 173 K to 1.0 ns at 248 K.

In liquid water, the excited OH-stretch vibration has a lifetime of 0.26 ps at 298 K and this increases to 0.32 ps at 358 K. The reason for this is due to the effects of the hydrogen-bonded network. The OH-stretch vibration normally relaxes by transferring energy to an overtone of the H-O-H bending vibration. However, as the temperature increases the hydrogen bonds of water get weaker, which leads to an increase of the frequency of the stretch vibration and a decrease of the frequency of the bending vibration. As a result, the overtone of the bending mode shifts out of resonance with the stretching mode, thereby making the energy transfer less likely."

P.S.: Gilt fuer Leitungs- und Mineralwasser!