Natural Science - Year II

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Science Web Assignment for Unit 48

 This Unit's Homework Page History Lecture Science Lecture Lab Parents' Notes

# Science Lecture for Unit 48: Helmholtz and Entropy

#### For Class

• Topic area: Physics: Thermodynamics
• Terms and concepts to know: Entropy, disorder, Second Law of Thermodynamics, Time's Arrow
• See historical period(s): 18th-19th Centuries

## The Laws of Thermodynamics

One of the great science writers of the twentieth century was the science fiction author, Isaac Asimov. Since his article on Thermodynamics is accessible and still considered a good introduction to the topic, I'm going to ask you to read the whole chapter....and not say very much more here. But do pay attention to the study questions below!

Read Asimov's explanation of Thermodynamics to help put the recent discussions in perspective.

• What happens to the temperature of the water when we add hot water to cold water?
• What are the three main ways that heat travels (and the temperature of something changes)?
• What happens to the heat energy that goes into making liquid water boil? Does all of the energy serve to increase the temperature of the water?
• What are conductors? insulators?
• Why are some substances better heat conductors than others?
• Why is heat always a side effect of any transfer of energy?
• Suppose that I have two steam engines, each with a boiler (hot region) and a condenser (cold region). In engine A, the boiler is 120°C and the condenser is 40°C. In engine B, the boiler is 130°C and the condenser is 50°C. Does one produce more energy than the other? Why?
• Does the conservation of energy apply to electrical and chemical energy, or only to heat energy?
• Why is it difficult to test the law of conservation of energy?
• How can the laws of thermodynamics be true if they were originally based on the theory of caloric, which we now know to be false?
• Can such a transfer result in a decrease in entropy? If so, under what conditions?
• What is Maxwell's Demon?
• How do you account for the increase in order represented by all life on earth, if the tendency of the universe it toward disorder?

### Study/Discussion Questions

• See the questions on Asimov's article!

### Further Study On your Own (Optional)

• The Wikipedia entropy article is pretty good and has links to further demonstrations.