Victory for the ACT Student Text 15e

S CIENCE R EVIEW • 351

Given the information from all three stations, which site(s) is (are) possible for the epicenter? A. I only B. III only C. I and III only D. II and III only If a fourth seismic station gave a report on this earthquake, at what point must its circle meet station A’s circle? F. I G. II H. III J. IV What is the minimum number of points where two circumferences from two seismic stations, both measuring the same earthquake, can meet? F. One G. Two H. Three Ǥ ϐ‹‹–‡ To investigate the factors affecting the rate at which starch is broken down to sugar by the digestive enzyme salivary amylase, two experiments were performed. In both experiments, starch (in the form of a cracker) was mixed in a beaker with the enzyme, and samples were removed and tested every 3 minutes. Special indicators were dipped in the sample to determine the presence of starch or sugar. Experiment 1 To test the effects of different pH levels on enzyme activity rate, one cracker and a standard amount of enzyme were placed in three beakers, each containing buffers of different pH. This procedure was repeated using standard amounts of water in place of the enzyme. All tests were carried out at optimal temperature. Starch and sugar levels (starch/sugar) from selected samples are shown in Table 1. Passage VIII TABLE 1 cracker + enzyme + buffer 5 7 9 high/none moderate/moderate high/none high/none low/high high/none high/low none/high high/low moderate/moderate none/high moderate/moderate cracker +water + buffer 5 7 9 high/none high/none high/none high/none high/none high/none high/none high/none high/none high/none high/none high/none 47. If a fourth seismic station gave a report on this earthquake, at what point must its circle meet station C’s circle? A. I B. II C. III D. IV 48. Contents of Beakers Approximate pH Levels Levels of Starch/Sugar After 3 minutes After 9 minutes After 15 minutes After 60 minutes

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Throwback to Science While reading an extended experiment like this one, it is helpful to note which factors play which roles during the experiment. Remember, a control is a factor that gives a source of comparison to the single independent variable so it is clear that the effects seen are coming from the independent variable. And an independent variable is the variable scientists change to see the effect on the dependent variable. Understanding these differences in the experiment can help you gain a better grasp of what is going on and can allow you to more quickly and accurately answer accompanying questions.