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GED Science Answers and Explanations

1. 1: The velocities of both the wind and the aircraft can be represented by vectors, with the length of the vector representing the speed and the direction of the vector representing the direction of either the wind or the airplane. Since the wind speed opposes that of the plane, the pilot will measure the sum of the actual wind speed plus that of his aircraft:

2. 3: The chart shows that plastic and cardboard materials both comprise 15% of the collected materials, so it is incorrect to say that there is more plastic than cardboard. They are present in equal quantities.

3. 2: Oogenesis is the process that gives rise to the ovum, or egg, in mammals. The oocyte is the immature egg cell in the ovary. In humans, one oocyte matures during each menstrual cycle. It develops first into an intermediate form called the ootid, and eventually into an ovum. The prefix oo- is derived from Greek, and means "egg."

4. 1: The reactions described in the text are ones during which negatively charged electrons are produced by a reaction that reduces the positively-charged lead anode. The reducing agent, in turn, is oxidized by this reaction. These electrons travel through the wire to the negatively-charged cathode, where they react with the sulfuric acid oxidizer and reduce it, forming lead sulfate. In a car battery, the anode is the positively-charged electrode, and is normally indicated by a red marking.

5. 1: In an oxidation reaction, an oxidizing agent gains electrons from a reducing agent. By contributing electrons, the reducing agent reduces (makes more negative) the charge on the oxidizer. In the car battery, reduction of the positively-charged anode provides electrons, which then flow to the cathode, where an oxidation takes place. In an oxidation, an oxidizing agent increases (makes more positive) the charge on a reducer. In this way, the extra electrons in the negatively charged cathode are neutralized by the surrounding oxidizing agent.

6. 4: The reaction described in the text is one during which two water molecules (H2O) are produced for each lead oxide (PbO2) molecule that reacts at the cathode.

7. 3: The data indicates that up until about 4 weeks, the silk production from both colonies was similar. This suggests that the worms from each colony produced the same amount of silk, and that choices A and B are incorrect. The data does indicate that, over the long term, the silk produced by the entire colony of genetically diverse worms was greater than the silk produced by the entire colony of genetically uniform worms. This might be because the worms produce for a longer time, or because of some other mechanism. The experiment does not indicate what that mechanism might be.

8. 2: The increase in productivity from the diverse culture occurs at about 4 weeks, coinciding with the time at which new worms are hatched and begin to produce silk.

9. 1: The digestion of starch begins with its exposure to the enzyme amylase, which is present in the saliva. Amylase attacks the glycosidic bonds in starch, cleaving them to release sugars. This is the reason why some starchy foods may taste sweet if they are chewed extensively. Another form of amylase is produced by the pancreas, and continues the digestion of starches in the upper intestine. The di- and tri-saccharides, which are the initial products of this digestion, are eventually converted to glucose, a monosaccharide that is easily absorbed through the intestinal wall.

10. 4: The term hydrologic cycle is defined in the first paragraph, where it is described as being equivalent to the water cycle. It is derived from the Greek root hydros, which means "water."

11. 2: The second paragraph gives examples of different storage reservoirs for water in the water cycle. Underground aquifers are one of the examples given. An aquifer (a word derived from the Latin root aqua, meaning water) is any geologic formation containing ground water.

12. 5: According to the table, the average residence time of water in soil is only two months. Only its residence time in the atmosphere, 9 days, is shorter. Residence time is defined in the text as the average amount of time that a water molecule spends in each of the reservoirs shown in the table before it moves on to the next reservoir of the water cycle.

13. 2: According to the final paragraph of the text, ocean levels actually fall during an ice age. This is because more water is stored in ice caps and glaciers when the prevailing temperatures are very cold, so less water remains in the oceans.

14. 3: Because the addition of heat causes the molecules of a substance to increase their rate of motion, it is considered a form of kinetic energy. The temperature of a substance is proportional to the kinetic energy of the molecules of which it is made. Addition of heat to a system usually results in an increase in temperature, but temperature is not a form of heat. It is a measure of the amount of kinetic energy present in a system.

15. 3: Energy in the form of heat is always absorbed by the molecules of a substance to make them move faster. During a change of state, some molecules are absorbing energy and escaping the solid phase to become liquid, or escaping the liquid phase to become gas. Since molecules in a gas move faster than those in a liquid and molecules in a liquid move faster than those in a gas, the average speed increases. Note that choice E is incorrect since the heat of vaporization for water is greater than its heat of fusion.

Last Updated: 05/15/2014

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