Embracing Complexity

Heat Engines Violate the Second Law of Thermodynamics

Violations of the second law of thermodynamics would be obvious if it were not for misleading education of this kind:

"A necessary component of a heat engine, then, is that two temperatures are involved. At one stage the system is heated, at another it is cooled."

This is simply not true. There are heat engines functioning in isothermal conditions - the work-producing force is activated by some chemical agent, not by heating. Here are examples of macroscopic contractile polymers which, on adding acid (H+) to the system, develop a huge work-producing force, contract and lift a weight:

Work-producing force increases on acidification

"When the pH is lowered (that is, on raising the chemical potential, μ, of the protons present) at the isothermal condition of 37°C, these matrices can exert forces, f, sufficient to lift weights that are a thousand times their dry weight. This is chemomechanical transduction..."

FIGURE 4: "Polyacid gel in sodium hydroxide solution: expanded. Polyacid gel in acid solution: contracted; weight is lifted."

FIG. 16A on p. 11025 in J. Phys. Chem. B, 1997, 101 (51), pp 11007-11028, Dan W. Urry, Physical Chemistry of Biological Free Energy Transduction As Demonstrated by Elastic Protein-Based Polymers

The following four-step isothermal reversible cycle clearly violates the second law of thermodynamics:

1. The polymer is initially stretched. We add H+ to the system.

2. The polymers contracts and lifts a weight.

3. We remove the same amount of H+ from the system.

4. We stretch the polymer and restore the initial state of the system.

Note that adding H+ to the system and then removing it (steps 1 and 3), if performed reversibly, amount to zero work involved (there are minor variations related to the nature of the polymer which can be shown to be insignificant).

Pentcho Valev