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# Ch 3 - Chapter3 ReviewQuestions:PossibleAnswers 1 What are...

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Chapter 3 Review Questions: Possible Answers 1. What are the six key elements in living organisms, and where does each occur—in the atmosphere, hydrosphere, or lithosphere? Nitrogen, carbon, oxygen, hydrogen, phosphorus, and sulfur are the key elements in nature. Each is found in all living things and detritus. All six elements are found in the atmosphere, hydrosphere, and lithosphere. Carbon is primarily found in the atmosphere. Phosphorus and sulfur are primarily found in the lithosphere. 2. What is the “common denominator” that distinguishes between organic and inorganic molecules? The common denominator that distinguishes organic and inorganic molecules is carbon- carbon, carbon-hydrogen, and carbon-oxygen bonds. 3. In one sentence define matter and energy, and demonstrate how they are related. Matter is anything that occupies space and has mass, while energy is the ability to move matter. “On a molecular level, changes in state are actually movements of atoms or molecules. For instance, the degree of heat energy contained in a substance is a measure of the relative vibrational motion of the atoms and molecules of the substance.” 4. Give four examples of potential energy. In each case, how can the potential energy be converted into kinetic energy? Water behind a dam—release the water. Coal—burn the coal. A stretched rubber band— release the rubber band. A leaf attached to a tree—the leaf falls. 5. State the two energy laws. How do they relate to entropy? The First Law of Thermodynamics: “Energy is neither created nor destroyed, but may be converted from one form to another.” The Second Law of Thermodynamics: “In any energy conversion, some of the usable energy is always lost.” “Entropy is a measure of the degree of disorder in a system, so increasing entropy means increasing disorder. With energy inputs, everything goes in one direction only toward increasing entropy.” The lost energy described in the second law is the disorder. In order to keep anything organized, you must put energy in because everything moves to disorder. Energy that has been converted from one form to another may include heat energy. As heat dissipates it disperses, thus becoming more disordered. 6. What is the chemical equation for photosynthesis? Examine the origin and destination of each molecule referred to in the equation. Do the same for cell respiration. Photosynthesis : Carbon dioxide plus water plus sunlight gives glucose plus oxygen. The carbon dioxide originates from respiration, including the burning of glucose in cells, decomposition, the burning of biomass and fossil fuels, and so forth. Water originates from soil, streams, and so forth in the hydrological cycle. The oxygen that is released is used in combustion and in respiration. The glucose is burned during respiration.

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