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performed on scatter plots. Here is an example. The scatter plot shows the concentration of a reactant (con- sumed in a chemical reaction) as a function of time. Notice that data were not taken at the beginning of the experiment (zero seconds) and beyond 500 sec- onds. If you assume that the thick line will maintain its shape in both directions, you can solve this problem. At the beginning of the experiment the concentration of the reactant was at a maximum. Therefore, it had to be higher than 0.15 mol/liter. If you extend the thick data line to the y-axis (the gridline corresponding to zero seconds), while maintaining the shape of the curve, you can estimate the initial concentration of the reac- tant was about 0.18 mol/liter. How about the concentration at 600 seconds? At 300 seconds, the concentra- tion of the reactant seems to have leveled of at 0.05 mol/liter.It stays the same at 400 seconds, at 450 seconds, and 500 seconds. Wouldn’t you bet that the concentration will remain 0.05 mol/l at 600 seconds? DRAWING CONCLUSIONS To draw a conclusion, we take all available facts into account, and make a decision or statement based on all these facts put together. Question: Did he do it? Facts: The accused had a motive, no alibi, and the unfortunate luck of being seen by the nosy neighbor. Conclusion: The accused is guilty. In the case of science, in very much the same way, we need to pull all the information available together, sum it up, and make a judgment or prediction. Example 1 Question: If you were looking for a metal whose heat transfer properties didn’t vary much over a wide range of temperature, which metal from the list in the preceding example would you use? Concentration of a Reactant as a Function of Time 0.20 0.15 0.10 0.05 0.00 0 100 200 300 400 500 600 Concentration [mol/liter] Time [s] – ACT SCIENCE REASONING TEST PRACTICE– 269 Facts: Thermal conductivity of platinum hardly changes with temperature. The variation of other metals with temperature is greater. Conclusion: Platinum. Example 2 Facts: The average woman ovulates on the 14th day of her cycle. Release of the ovum from the ovary is hormonally stimulated. Question: Which hormone is most responsible for ovulation? More facts (after looking at the scatter plot): The concentration of LH, rapidly increases from the day 11 to day 13 of the cycle, immediately preceding the ovulation event, and then it rapidly drops. Conclusion: The concentration of LH increases to stimulate ovulation. Once ovulation occurs, the concentration of LH decreases, since more stimulation is not required. One ovum is enough. Summary In this lesson you learned about different types of graphical representation, including tables, scatter plots, bar graphs, pie graphs, and diagrams. You now have an idea of which graphical representation is most useful for a given scenario, that for example, pie graphs are used to show the portion of a whole taken up by a subset of that whole. You know how to locate the essential elements of graphical representation (axes, labels, titles, and legends), and how to find and interpret the information you are asked about. You can look for trends (such as increasing and decreasing), compare different sets of data, interpolate and extrapolate, as well as draw conclusions and make predictions. However, having these skills up your sleeve is only a start, you will need a great deal of practice. (See page 283 for ACT Science Reasoning Test practice questions.) RESEARCH SUMMARIES Research Summary passages require you to read one or more related experiments and to analyze them to cor- rectly answer the questions that follow. Each experiment has more or less the same structure. There is a pur- pose—to prove or disprove some hypothesis, to determine what material is best for an application, what conditions are favorable, or to find what might be causing problems with an experiment. This lesson will help you develop skills you will need to: ■ read and understand descriptions of one or more related experiments. ■ draw conclusions and make predictions based on the research results. Reading with Understanding As you are reading descriptions of experiments, stay focused on what you are reading by underlining key con- cepts, making notes on the side of the text, and keeping the following questions in mind: – ACT SCIENCE REASONING TEST PRACTICE– 270 ■ How many experiments are discussed in the passage? ■ What is the purpose of the experiment(s)? ■ What are the variables in the experiment? ■ Which variables are controlled by the scientist, and how? ■ Which variables are measured or observed, and how? ■ Were any calculations performed? ■ Is there an experimental control? If so, what is it? ■ If more than one experiment is presented, how is each experiment similar/different? Take a look at the following example: Example 1 A student working in an optics lab needs a filter that will transmit (pass through) more than 90% of green light, while absorbing (getting rid of) 95% of near-infrared light. She finds six filters in the lab, but they are not labeled, so she is not sure whether any of them will work. She has a 632 nm green laser, a 1,064 nm near-infrared laser, and a suitable detector. She decides to measure the intensity of each laser with the detector, and then to mount different fil- ters in the path of each of the lasers, recording the transmitted intensity with the detector. The data she obtains are tabulated below: Initial Transmitted Intensity Intensity [Units of [Units of % Light % Light Filter Laser Intensity] Intensity] Transmitted Absorbed 1 near IR 500 35 7 93 2 near IR 500 200 40 60 3 near IR 500 15 3 97 4 near IR 500 300 60 40 5 near IR 500 100 20 80 6 near IR 500 400 80 20 – ACT SCIENCE REASONING TEST PRACTICE– 271 Initial Transmitted Intensity Intensity [Units of [Units of % Light % Light Filter Laser Intensity] Intensity] Transmitted Absorbed 1 green 400 358 92 8 2 green 400 320 80 20 3 green 400 388 97 3 4 green 400 280 70 30 5 green 400 160 40 60 6 green 400 80 20 80 Have you read the passage and looked at the data carefully? Answer the relevant questions listed at the beginning of the lesson. 1. How many experiments are discussed in the passage? Just one. 2. What is the purpose of the experiment(s)? To find a filter that satisfies specified criteria. 3. What are the variables in the experiment? There are six different filters and two different lasers (of different intensity and wavelength—green and near-IR). Amount of different type of laser light transmitted by a particular filter is also a variable. 4. Which variables are controlled by the scientist and how? The wavelength is controlled, using two different lasers. Different filters are aligned in the path of the lasers. 5. Which variables are measured or observed and how? The initial intensity of each laser is measured using a detector. Intensity of light (for each of the lasers) transmitted through each filter is measured using the detector as well. 6. Are any calculations performed? The table lists the percentages of light transmitted and light absorbed. That information was neither meas- ured nor given, so it must have been obtained using a calculation. – ACT SCIENCE REASONING TEST PRACTICE– 272 As you can see, quickly answering for yourself these few simple questions enables you to determine the functions of different parts of the experiment, and to stay focused on what is important. Here is another example: Example 2 Meal moths are one of the most common pantry pests. They often nest in flour, cereal, pasta, seeds, and dried fruits they find in kitchen and pantry cabinets. A scientist decided to compare the effec- tiveness of different methods of ridding the household from this pest. The scientist wanted to know how the total number of adult moths would vary over time when 1. all food is removed. 2. a commercial pesticide is used but ample food is provided. 3. bay leaf, an alleged natural moth repellant is used but ample food is provided. 4. all food is removed and a commercial pesticide is used. 5. all food is removed and bay leaf is used. 6. ample food is provided and no pesticide or repellant is used. For each of the six experimental settings, the scientist designed a closed container (10 cubic feet) with ample air supply, and conditions such as temperature and light adjusted to resemble an aver- age kitchen. He then placed 10 adult moths (both male and female) in each container, along with the appropriate amount of food and bay leaf. He sprayed pesticide in the containers of Group 2 and 4 once a day. The data he collected over 7 days are tabulated below. GROUP CONDITIONS NUMBER OF ALIVE ADULT MOTHS Food taken Bay away leaf Pesticide Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 1 YES NO NO 10 8 3 1 3 0 0 2 NO NO YES 10 6 5 3 6 8 9 3 NO YES NO 10 8 8 7 8 7 6 4 YES NO YES 10 6 3 1 1 0 0 5 YES YES NO 10 8 3 1 0 0 0 6NONONO10101010121212 – ACT SCIENCE REASONING TEST PRACTICE– 273 Now that we have read the passage, underlined or marked key information, made notes in the margins of the text, and analyzed the data in the table, answer the relevant questions from the beginning of the lesson: 1. How many experiments are discussed in the passage? Only one. 2. What is the purpose of the experiment(s)? To compare the efficiency of different methods of meal moth extermination. 3. What are the variables in the experiment? The variables are food, pesticide, bay leaf, time, and the number of moths in a container. 4. Which variables are controlled by the scientist and how? The scientist controls the contents of each container—food, pesticide, bay leaf, and the initial number of moths. 5. Which variables are measured or observed and how? The number of moths in each container is observed over the course of seven days. 6. Were any calculations performed? No calculations were performed. 7. Is there an experimental control? If so, what is it? The experimental control is the group of moths (6) in the container where ample food is available, and no pesticide or bay leaf is present. It corresponds to the situation where nothing is being done to eliminate the moth population. You may still not understand all the details of this experiment, but the questions above probably helped you organize the information that was presented to you, and you can now proceed to the more challenging task of interpreting the experiments and the experimental results. Analysis When reading Research Summary passages you will have to think about the following questions: What do the results show? What do they mean? How does the measured or observed variable depend on the controlled variable? Let’s look at the data in Example 1. What can we say about the tabulated information? First, there are two different tables. One is for the data taken using the near-IR laser, and the other for data taken using the green laser. The initial intensities of the two lasers are different, the near-IR has an intensity of 500 units, while the green has an intensity of 400 units, but the initial intensity of each laser does not change. The higher the transmitted intensity, the higher the percent transmitted. In fact, the percent transmitted is the ratio of the – ACT SCIENCE REASONING TEST PRACTICE– 274 . 8 9 3 NO YES NO 10 8 8 7 8 7 6 4 YES NO YES 10 6 3 1 1 0 0 5 YES YES NO 10 8 3 1 0 0 0 6NONONO10101010121212 – ACT SCIENCE REASONING TEST PRACTICE– 273 Now that we have read the passage, underlined. near IR 500 35 7 93 2 near IR 500 200 40 60 3 near IR 500 15 3 97 4 near IR 500 300 60 40 5 near IR 500 100 20 80 6 near IR 500 400 80 20 – ACT SCIENCE REASONING TEST PRACTICE– 271 Initial Transmitted Intensity. green 400 358 92 8 2 green 400 320 80 20 3 green 400 388 97 3 4 green 400 280 70 30 5 green 400 160 40 60 6 green 400 80 20 80 Have you read the passage and looked at the data carefully? Answer