What the Second Law Does Say

This post is part of a series, Nonsense and the Second Law of Thermodynamics.  The previous post is entitled:  What the Second Law Does Not Say.

There are multiple valid ways to state the second law of thermodynamics.  Some ways of expressing the law do so in terms of macroscopic notions such as heat and temperature.

Other descriptions employ the concept of entropy, which is based upon a statistical approach to thermodynamics. Some alternative macroscopic statements include:

• There can be no process with the sole result of absorbing heat and completely converting it into work.
• It is impossible to convert heat completely into work in a cyclic process.
• It is impossible to carry out a cyclic process using an engine connected to two heat reservoirs that will have as its only effect the transfer of a quantity of heat from the low-temperature reservoir to the high-temperature reservoir.

What the Second Law Does Not Say

This post is part of a series, Nonsense and the Second Law of Thermodynamics.

The Second Law does not say it is impossible for heat to be transferred from a cold body to a hot body.  The second law does not say that "disorder" must increase on the earth or anywhere else.  Life is not a counter-example to the second law; life is an example of the second law in action.

One has to be very careful about applying statistical results to a single molecule or a few molecules and remembering that increasing entropy applies to irreversible changes, not reversible ones. The second law says nothing about disorder. The second law does not prevent evaporative coolers from operating.

The second law does not contradict radiative transfer theory or global warming. The second law does not contradict conservation of energy.  In applying the second law to  cosmology, one should tread cautiously.

Nonsense and the Second Law of Thermodynamics

Introduction

The Second Law of Thermodynamics is, perhaps, the most abused physical law of all time. It may be rivaled for that distinction by the Uncertainty Principle, Relativity, and Hawking Radiation, but I think the Second Law probably wins the contest.

There is a plethora of nonsense disseminated on the web and elsewhere that misrepresents what the law actually says. This series is an attempt to curb some of that nonsense.  Along the way, I hope to make some sense of what the second law of thermodynamics actually does say, as well as addressing some of the nonsense that people believe about it.

Reformatted Post on Beer's Law

I have had to reformat the post on Beer's Law.  The html editor at Blogspot seems to do strange things with <br> tags.

Bush on Islam

"The face of terror is not the true faith of Islam. That's not what Islam is all about. Islam is peace. These terrorists don't represent peace. They represent evil and war. When we think of Islam we think of a faith that brings comfort to a billion people around the world. Billions of people find comfort and solace and peace. And that's made brothers and sisters out of every race -- out of every race. America counts millions of Muslims amongst our citizens, and Muslims make an incredibly valuable contribution to our country. Muslims are doctors, lawyers, law professors, members of the military, entrepreneurs, shopkeepers, moms and dads. And they need to be treated with respect. In our anger and emotion, our fellow Americans must treat each other with respect."

- George W. Bush 17 September 2001

Very Unscientific Poll

I have posted  a poll on global warming on this blog.  Before I remove the poll from the blog, I thought I should document the results.  The poll is for entertainment purposes only.  There was no methodology used except to post the poll to this blog using a blogger add-on.

The poll states "Global Warming is," and gives six options, "anthropogenic," "natural," "a hoax," "something I don't understand," "a topic upon which I am reserving judgment," and "other."

How To Convert To and From Parts-Per-Million (ppm)

Parts-per million (ppm) is a common quantity used in many areas of math and science.  It can be somewhat difficult for some to understand because it is not a true unit.  In fact, ppm is a unitless quantity.  It is analogous to percent.  Percent can refer to just about anything.  Percent means part-per-hundred, per cent (cent meaning hundred).  ppm is an exactly analogous quantity, but it is one part per million instead of one part per hundred.  ppm is a ratio between two numbers that have the same units.  Consider the example of a 5% sales tax.  For every hundred dollars I spend, I must pay 5 dollars in sales tax. So:

      5 dollars/100 dollars = 5%


I would much rather pay a 5 ppm sales tax:

     5 dollars/10⁶ dollars = 5 ppm   

We do not usually refer to money in ppm, but we could.  Ppm is more often found as a concentration, for example, ppm by mass or ppm by volume (sometimes referred to as ppmv).  In nuclear magnetic resonance spectroscopy ppm can be used to describe the amount of chemical shift in frequency (Hz/MHz).  This post focuses on the use of ppm as a measure of concentration.