The following practice questions start you off with some nifty graphics showing different energy systems. The first question tests your knowledge of the first law of thermodynamics, while the second one looks at the properties of water and steam.
Practice questions
The first question refers to the following diagram from NASA’s Glenn Research Center website.
Illustration courtesy of NASA.- Circle the vessel on the diagram with the higher temperature.
The next question refers to the following diagram, which is excerpted from Physical Science: What the Technology Professional Needs to Know, by C. Lon Enloe, Elizabeth Garnett, Jonathan Miles, and Stephen Swanson (John Wiley & Sons, Inc.).
- What properties of water and steam allow Newcomen’s steam engine to operate?
A. Water is heavier than steam. B. Steam condenses when cooled, occupying less space. C. The boiler provides the energy to move the pump. D. The pump rod is heavy enough to pull the arm down.
Answers and explanations
- The correct answer is State 1.
State 1 should be circled because it has the higher temperature. According to the diagram, the heat transfer, Q, would be from State 1 to State 2, indicated by the arrow labeled Q.
- The correct answer is Choice (B).
In the steam engine, water cools the steam, which then condenses, occupying less space. This action starts the entire cycle over again. You can eliminate the other answer choices when guessing is necessary. Choice (A) is incorrect because water and steam are both water, in different states. Their densities may be different, but their weights are the same. Only the volume differs when water turns to steam. Choice (C) is incorrect because the boiler doesn’t provide the energy to move the pump, which you can see by looking at the diagram. Choice (D) isn’t based on information given in the diagram. Nowhere are you told the weight of the pump rod.
