Stretching rubber bands and proteins, bottle rockets and open eyes under water

The main point of this lecture is to give you examples of how to "attack" and treat new problems.

Lecture notes

Video on stretching polymers


Imagine that you suspend a small weight in a rubber band and leave it there for a few minutes. Then you heat the rubber band with a hairdryer. Will the weight

A) not move?     B) move upwards?   c) move downwards?


A bottle rocket is driven by the expansion of the gas at high pressure P. Consider this gas as your thermodynamic system. What assumptions can you make about this expansion? (More than one answer can be correct)

A) it is quasistatic   B) it is isothermal   C) it is heat absorbing   D) it is adiabatic   E) it is isentropic   F) Q=0  G) W>0  H) W<0   I) none of the answers


Video on bottle rockets


The two halves of a sealed container are separated by a fixed semi-permeable membrane.  There are two species of molecules in the container, C (cubes) and D (disks). The membrane is permeable to the disks only.  Each half of this system has two different chemical potentials, one for disks and one for cubes: and

Given the constraints imposed, does this system appear to be in equilibrium?   (Hint: How do the ’s on the right and left compare? What about the ’s?)

A) Yes, it looks close to equilibrium   

B) No, it is obviously way out of equilibrium, so the system will look different a short time later.


Video on opening your eyes under water

Publisert 16. sep. 2020 12:25 - Sist endret 16. sep. 2020 12:25