Thermodynamics Quiz

Creationists who think that evolution violates the 2nd Law of Thermodynamics, evolutionists who think that it doesn't, anyone with a viewpoint on the issue, or anyone who is curious and would like to understand: This quiz is for you.

If you know your basic thermodynamics, you should have no problem with this quiz, and the quiz will answer whether evolution thermodynamics does violate the 2nd Law. The material covered in this quiz is taught within the first few weeks of an introductory thermodynamics class, and consists of the concepts of energy, absolute temperature, and entropy. If you can't answer these questions correctly, then you don't really understand thermodynamics.

The basic statement of the second law of thermodynamics is in the form of an inequality, so some of these answers should be expressed as inequalities. Ready? Let's begin:

  1. A body with temperature 6000 degrees Kelvin (K) loses 6000 Joules (J) of heat. Assume that the body is so massive that its temperature can be treated as constant. What is the change in entropy of the body?
  2. Suppose the heat lost is due to radiation of light. What is the energy of the light that was radiated?
  3. What is the entropy change of the system including both the light and the body?
  4. Therefore, how much entropy is carried by the light?
  5. Another body has temperature 300 K, and absorbs the light. How much does the body's energy increase?
  6. How does the second body's entropy change in each of the following cases?
    A. The energy of the absorbed light is immediately distributed throughout the body, so that the temperature remains virtually constant.
    B. The light is absorbed by only a very tiny bit of matter right at the surface. The matter heats up enormously right at that instant, and vaporizes, expands, floats up in the air, etc. (Think of evaporating water.)
  7. The second body on the average maintains a constant temperature of 300 K. There are day-to-day and seasonal cycles, but on the average the temperature is constant. How much of the absorbed energy must it ultimately lose?
  8. The second body loses the energy by radiating infrared light. This is heat loss, so how much does the entropy of the body change? Again, assume that the body is so massive that the temperature remains approximately constant at 300 K during the heat loss.
  9. What is the net entropy change due to the combined absorption and radiation? Use the conditions from question 6B.
  10. The sun's surface temperature is approximately 6000 K. The earth's surface temperature is approximately 300 K. Three-fourths of the earth's surface is water. Sunlight warms the earth's surface and evaporates water. The earth's surface cools by radiation. Does the second law of thermodynamics allow entropy on the earth to decrease?

If you wish, email me with your answers (as well as your comments), and I will check them.