Question 1 is asking a pretty straight from the reading type question, but the data tables could also be used to help answer this question. The question asks what the difference is between experiments 1 and 2. Therefore, there is no need to even look at experiment 3. When questions of this nature are asked, it is almost a waste of time to read each choice. First, go back to the passage and look at experiment 1. What is it about? From the reading, we find that this experiment deals with temperature change. Then, what about experiment 2? This single sentence description reveals that the temperature remains the same, while the diameter of the tube changes. Back to the question, then. The question is written so that the variable for experiment 1 would be outlined first - temperature variation. Any choice without that at the beginning is automatically crossed out. So, B and C are pointless. We found that experiment 2 deals with variation in tube diameter; thus, choice A has to be correct! It meets both conditions.
Question 2 requires us to recall the conditions again to see which sets are the same. First, they way that they use sets here is that each individual test is a "set." Each experiment was performents with 4 trials, or sets. So, experiment 1 contains sets 1-4, experiment 2 has sets 5-8, and experiment 3 has sets 9-12. There are 2 ways to approach this question. One way is to look at each data table and see which of the sets have identical variables, but this could take time when comparing 12 sets.
A better way is to determine the variables given in the description of each experiment. In experiment 1, the changing variable is the temperature by 10 degrees from 20-50 degrees Celsius. The distance between the swabs of 10 cm and the 1 cm diameter of the tube are all constant for each of the 4 sets. None of the trials in table one are the same. For experiment 2 the diameter of the tube changes by 0.2 for each trial, starting at 1.0 cm (the only trail in experiment 2 that is similar to experiment 1). Additionally, the temperature of experiment 2 was maintained at 20 degrees, just like set 1 in experiment 2. Probably a flaw in test writing, the Experiment 2 set up does not describe the distance between the swab, so we assume that it has not changed from experiment 1. So far, we note that Set 1 and 5 are the same!
Looking at experiment 3, we see that the changed variable is the distance between the swabs. The controlled or fixed variables are the diameter of the tube (1.0 cm) and the temperature is assumed to remain at 20 degrees, in that this experiment claims to be the same as experiment 2 except for the diameter remaining fixed, and the distance between swabs being varied. We know that the distance between the swabs in experiments 1 and 2 was constant at 10 cm. Thus, set 9 must be the third identical condition. Looking back at sets 1, 5, and 9, you'll note that even the data collected for them are identical! So, the correct answer is G.
Question 3 asks us to look at the data table for Experiment 1 and graph the relationship between temperature and the distance from HCl that the reaction occurred. The table shows that the time for these reactions to occur is varied, but those data points are not relevant. The distance, however, remains constant, even as the temperature increases. Notice, all of the graphs show temperature on the x axis from 20-50 degrees C. So, this axis cannot help us narrow the selection. Too, the Y axis shows distance increasing from the HCl swab, where 0 would likely imply that the reaction occurred right at the swab. We make this conclusion because the corner of the graph is going to be the lowest point, and we see the drawn in arrow pointing "up" toward higher measurements. We've already concluded that the distance measurements do not move considerably. Choice A suggests that the distance starts closer and with increasing temperature eventually becomes further away (not a constant distance). Choice B conveys the opposite where the distance starts further away, and moves closer to the HCl swab (still not a constant distance). Choices C and D have the only straight lines, which demonstrate that one of the 2 variables we are looking at (distance and temperature) does not change. Choice C, however, actually indicates that the temperature does not change and the distance does - neither which support the data on the table. Choice D, though, displays the correct graph, indicating that regardless of the temperature, the distance is not changed.
Question 4 will require more thought and a little math, rather than inference, as requested from the first 3 questions. Basically, they want to know that if there had been a trial 10.5 sneaked in between trials 10 and 11, where the swabs were 25 cm apart, what would be the distance from the HCl swab where the reaction takes place be? Take a look at the data table 3. What is the difference in distance between trials 9 and 10? - About 4. What about between 10 and 11? - About 4? What about between trials 11 and 12? -4! We notice a pattern. For every 10 cm the swabs move apart, the distance from the HCl swab and the reaction point is increased by 4 cm. Therefore, we have to think about this - what happens if we increase just half the distance - by 5 cm instead of 10? Then, it would stand to reason that the distance from the reaction point and the HCl swab would be half as much also, reducing from 4 to 2. So, if we are sneaking in a point just 5 cm from the trial 10's distance of 25 cm between the swabs, where the reaction point and the HCl swab were about 8 cm apart, then we can interpret that the distance between the reaction point and the HCl swab at 25 cm would be 10 (because 8 plus 2 = 10), meaning that choice G is correct. This could be verified by creating a graph, similar to how the graph for choice A in question 3 looks as well.
Question 5 is one where 2 choices are a little easier to eliminate if you remember the experiments. In experiment 1, remember, we already looked at temperature. So, when the question asks what the student will test that was not yet tested, choice C, "temperature" is clearly not the right answer. Similarly, choice D suggests that the tube diameter should be tested, but that was the goal for experiment 2. So, the remaining choices are A "atmospheric Pressure" and B "Length of the tube." Length of the tube, though, will actually just be compare how far apart the swabs are - which was the purpose of experiment 3. Therefore, the only choice that was not actually already tested is choice A - atmospheric pressure.
Question 6 states that the student makes a clam that the NH3 diffuses at a greater rate than the HCl. What does that actually mean? Well, a "greater rate" really just means that it moves faster. So think about what that means in the context of the question. The whole point of the tests was to see which of the 2 gas vapors moved at a faster rate. The student knew that when the 2 gasses met at the same place, there would be a white ring that formed. So, they dipped separate swabs in each material, and then confined the swabs to a tube to better measure where the reaction occurred. This could tell them how far each gas actually traveled before meeting the other. For a frame of reference for their measurement of distance, they chose to always measure the distance of the reaction from the HCl swab. The set up would look similar to my simple illustration below.
Looking at the all of the data collected from trials 1-9, we notice that the distance from the swab to were the gasses meet and cause a reaction is ALWAYS less than half of the distance between the two swabs. What this means, then is that the NH3 travels a further distance in the same amount of time that the HCl does, thus causing the reaction to occur closer to the HCl swab than the NH3 swab. Then, since objects that move further in the same amount of time are known to move faster than objects which move a lesser distance in that same time, we can support the students claim that NH3 vapors do actually move faster than HCL vapors. Choice J then, is the correct answer.
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