# Tag Info

2

Ever heard of the cosmic microwave background? The CMB is a relic from when the universe became "opaque" - when, as Wikipedia says, protons and electrons combined to form neutral atoms. These atoms could no longer absorb the thermal radiation, and so the universe became transparent instead of being an opaque fog. So photons decoupled and the CMB was ...

2

This relation is not true for general processes. For a closed system, the general relation is $\delta Q \leq TdS$, as is illustrated by the Clausius Theorem (http://en.wikipedia.org/wiki/Clausius_theorem). Another way of writing it is $dS=\delta Q/T + dS_{irr}$ where $dS_{irr}$ is the entropy change due to irreversibilitiy in the closed system ...

1

Wikipedia Intensive and extensive properties By contrast, an extensive property is one that is additive for independent, noninteracting subsystems.[1] The property is proportional to the amount of material in the system. For example, both the mass and the volume of a diamond are directly proportional to the amount that is left after cutting it ...

1

In thermodynamic equilibrium, the solidification process can be tracked using the phase diagram of water and salt. One example (from wikipedia) is: It is fairly straightforward as a binary phase diagram. Above 0C, adding NaCl to water results in complete dissolution until somewhere above 26.3 wt.%. At that point, trying to stir more in will result in ...

1

Interesting question. I would have thought that if you were aware of the exact number of energy states and the populations thereof, you could apply boltzmann statistics to each of the levels in order to fit an appropriate temperature to the population in each state. This temperature, if comparable amongst the included levels, would therefore require that the ...

Only top voted, non community-wiki answers of a minimum length are eligible