Saturday, July 23, 2005
A crazy Chemistry class
It went something like this:
At normal atmospheric pressure, the spaces between gas molecules are so large that intermolecular attractions are negligible.
As the applied pressure increases (up to 350 atm) the volume of the sample decreases, and the average intermolecular distance becomes smaller.
At these higher pressures, a molecule approaching the container wall is attracted by nearby molecules, which lowers its speed and lessens the force of its impact [on the wall].
So, first the molecules go further apart, but are then drawn back together. What do we call this? Absence makes the heart grow fonder.
[at this point, groans are resounding all about the classroom; we used the Physics lab]
Now, if you walk past your friend quickly, can you shake hands and say hello? No. Likewise, molecules at higher temperatures, which have higher kinetic energy, cannot form bonds. Because they move too fast.
But if you walk slowly, can you shake hands? Yes, and you can say hello and form... BONDS! [he has this habit of ending sentences with fortissimo, staccato-ed words].
So yes, that was mostly it. But I thought of another, having been pulled into this frame of thought by our rather lame teacher.
Here's the concept: As the free volume in which the molecules can move becomes smaller [because volume decreases with pressure increase], the molecules become closer to one another such that repulsive forces occur between them.
Here's the proverb: Familiarity breeds contempt.
Posted by SimianD at 9:59 AM