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# Thermodynamics

## How important are the laws of thermodynamics?

A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is the scientific equivalent of: Have you read a work of Shakespeare’s?

– C. P. Snow, 1959 Rede Lecture, “The Two Cultures and the Scientific Revolution”.

## Zeroth law of thermodynamics

### Thermal equilibrium (in this example) is reached when the temp of all pieces = 13.4 degrees C.

http://weelookang.blogspot.sg/2012/09/the-zeroth-law-of-thermodynamics.html

### “When body A is placed in thermal contact with body B, there will be a flow of thermal energy between the two bodies. Thermal energy will flow from the body at a higher temperature, to the one at a lower temperature, until thermal equilibrium between the two bodies is reached.” – Loo Kang Lawrence

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2nd law

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## The second law is related to entropy

### We know from everyday experience how energy spreads out – and how it doesn’t. This ice melting looks normal.

commons.wikimedia.org/wiki/File:Melting_icecubes.gif

## Entropy of perfume spreading in a room

### Yet it never happens. Why? Because if all the perfume molecules were suddenly found within the initial volume element it would be a violation of the Second Law of Thermodynamics.

This pic is from http://www.physics.usyd.edu.au/teach_res/mp/doc/tp_equilibrium.htm

## Third law of thermodynamics

### OR

Or the 3rd law is decribed like this:

### the entropy of a perfect crystal approaches zero, as its temperature approaches absolute zero.

What is the Third Law of Thermodynamics? Live Science

## Questions

In complete sentences or paragraphs, write your answers on a separate sheet of paper

1. Thermodynamics is based on ….

2. How is the zeroth law of thermodynamics like the simplest algebraic property?

3. In one sentence, describe the 1st law of thermodynamics

4. How do our bodies demonstrate the 1st law?

5. In one sentence, describe the 2nd law of thermodynamics

6. Click on the refrigerator link: explain how refrigerators work

7. Consider the image of the man tossing a bunch of bricks: how does this illustrate the concept of entropy?

8. Consider the animations of ice in water. According to Newton’s laws of motion, and laws of momentum, both cases are possible. Yet in the real world we only see one of these events happen. Why doesn’t the other event happen?

9. Consider perfume spreading in a room (you’ll need to watch it for a while to see the whole cycle) According to Newton’s laws of motion, and laws of momentum, all the perfume could eventually come back to where it started. So why doesn’t that happen?

10. According to the third law, what temperature can we never quite reach?

11. Click the link for perpetual motion machines. A perpetual motion machine of the first kind would be tremendous. Great. Beautiful. Amazing 😉 But it’s impossible: Explain why.

12. A perpetual motion machine of the second kind would also be great! And they seem reasonable: they do not violate the 1st law of thermodynamics/law of conservation of energy. But regrettably, this class of perpetual motion machines also doesn’t really work: Why not?

## Does 3rd law really exist?

On his website, physics teacher John S. Denker writes

Real thermodynamics is celebrated for its precision, power, generality, and elegance. However, all too often, students are taught some sort of pseudo-thermodynamics that is infamously confusing, lame, restricted, and ugly. This document is an attempt to do better, i.e. to present the main ideas in a clean, simple, modern way.

It is NOT optimal to formulate thermodynamics in terms of a short list of enumerated laws, but if you insist on having such a list, here it is, modernized and clarified as much as possible.

The zeroth law of thermodynamics tries to tell us that certain thermodynamical notions such as “temperature”, “equilibrium”, and “macroscopic state” make sense. Sometimes these make sense, to a useful approximation … but not always.

The first law of thermodynamics states that energy obeys a local conservation law. This is true and important.

The second law of thermodynamics states that entropy obeys a local law of paraconservation. This is true and important.

There is no third law of thermodynamics. [!!!] The conventional so-called third law alleges that the entropy of some things goes to zero as temperature goes to zero. This is never true, except perhaps in a few extraordinary, carefully-engineered situations. It is never important. See chapter 4. ( av8n.com/physics/thermo/s0t0.html)

To summarize the situation, we have two laws (#1 and #2) that are very powerful, reliable, and important (but often misstated and/or conflated with other notions) plus a grab-bag of many lesser laws that may or may not be important and indeed are not always true (although sometimes you can make them true by suitable engineering).

## Related articles

The Quantum Thermodynamics Revolution

## Quotes

If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

Sir Arthur Stanley Eddington, The Nature of the Physical World (1915), chapter 4

The second law of thermodynamics is, without a doubt, one of the most perfect laws in physics. Any reproducible violation of it, however small, would bring the discoverer great riches as well as a trip to Stockholm. The world’s energy problems would be solved at one stroke. It is not possible to find any other law (except, perhaps, for super selection rules such as charge conservation) for which a proposed violation would bring more skepticism than this one. Not even Maxwell’s laws of electricity or Newton’s law of gravitation are so sacrosanct, for each has measurable corrections coming from quantum effects or general relativity. The law has caught the attention of poets and philosophers and has been called the greatest scientific achievement of the nineteenth century. Engels disliked it, for it supported opposition to Dialectical Materialism while Pope Pius XII regarded it as proving the existence of a higher being.

• Ivan P. Bazarov, “Thermodynamics” (1964)

Nothing in life is certain except death, taxes and the second law of thermodynamics. All three are processes in which useful or accessible forms of some quantity, such as energy or money, are transformed into useless, inaccessible forms of the same quantity. That is not to say that these three processes don’t have fringe benefits: taxes pay for roads and schools; the second law of thermodynamics drives cars, computers and metabolism; and death, at the very least, opens up tenured faculty positions.

Seth Lloyd, writing in Nature 430, 971 (26 August 2004)

A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is the scientific equivalent of: Have you read a work of Shakespeare’s?

– C. P. Snow, 1959 Rede Lecture, “The Two Cultures and the Scientific Revolution”.

## External resources

### What is a simple definition of the laws of thermodynamics? PhysLink

http://www.nmsea.org/Curriculum/Primer/what_is_entropy.htm

http://entropysimple.oxy.edu/content.htm

http://study.com/academy/lesson/what-is-entropy-definition-law-formula.html

http://www.chem1.com/acad/webtext/thermeq/TE1.html

# Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS3-2. Develop and use a model to illustrate that energy at the macroscopic scale can be accounted for as either motions of particles and objects or energy stored in fields.
Clarification Statements: Examples of phenomena at the macroscopic scale could include evaporation and condensation, the conversion of kinetic energy to thermal energy,

HS-PS3-4a. Provide evidence that when two objects of different temperature are in thermal contact within a closed system, the transfer of thermal energy from higher temperature objects to lower-temperature objects results in thermal equilibrium, or a more uniform energy distribution among the objects and that temperature changes
necessary to achieve thermal equilibrium depend on the specific heat values of the two substances. Energy changes should be described both quantitatively in a single phase (Q =m·c·∆T) and conceptually either in a single phase or during a phase change.

Next Generation Science Standards

Influence of Science, Engineering and Technology on Society and the Natural World: Modern civilization depends on major technological systems. Engineers continuously modify these technological systems by applying scientific knowledge and engineering design practices to increase benefits while decreasing costs and risks. (HS-PS3-3)

Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system. (HS-PS3-3)

Energy cannot be created or destroyed—only moves between one place and another place, between objects and/or fields, or between systems. (HS-PS3-2)

AP Physics

7.B.2.1: The student is able to connect qualitatively the second law of thermodynamics in terms of the state function called entropy and how it (entropy) behaves in reversible and irreversible processes. [SP 7.1]
– AP Physics Course and Exam Description