ACT Prep - Experiments Round 1!

Transcription

1 ACT Prep - Experiments Round 1! An experiment was run to determine how temperature and the amount of sugar affect the rate at which sugar dissolves in water. Study 1 In the first experiment, a scientist changed the temperature of water in order to see how this affected the rate at which sugar dissolved in water. She set up 5 beakers with 500mL of water at various temperatures. She then measured the amount of time it took to dissolve 50 grams of sugar in each beaker of water. This was recorded as the dissolving time of sugar. The results are shown in Table 1. Beaker Temperature ( C) Dissolving Time of Sugar (sec) Table 1 1. According to Table 1, which of the following would most likely be the dissolving time of sugar when added to 500mL of water at 25 C? A. 25 seconds B. 29 seconds C. 45 seconds D. 57 seconds 2. If a beaker of 500mL of water at 60 C were added to Study 1, which of the following values would most likely be the dissolving time of the 50 grams of sugar added? A. 12 seconds B. 14 seconds C. 17 seconds D. 28 seconds Study 2 In the second experiment, the scientist changed the amount of sugar being dissolved in order to see how this affected the rate at which sugar dissolved in water. She set up 5 beakers with 500mL of water all at a temperature of 30 C. She then added different amounts of sugar to each beaker and measured the amount of time it took to dissolve. This was then recorded as the dissolving time of sugar. The results are shown in Chart 1. Chart 1 3. According to Table 1, which of the following is NOT a good estimation for the dissolving time of sugar at 37 C? A. 20 seconds B. 24 seconds C. 28 seconds D. 30 seconds 4. According to Chart 1, which of the following would most likely be the dissolving time of 55 grams of sugar in 500mL of water at a temperature of 30 C? A. 33 seconds B. 35 seconds C. 39 seconds D. 43 seconds 5. According to Chart 1, which of the following is a good estimation for the dissolving time of 5 grams of sugar in 500mL of water at a temperature of 30 C? A. 0 seconds B. 3 seconds C. 7 seconds D. 9 seconds

2 Experiment Passages. Experiment Basics: Make sure you identify: Common Questions: P - A - C - M - A - N -

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4 A scientist decided to perform an experiment to determine the relationship between exposure to microwaves and smartness of fish. To judge how smart the fish were she used a maze and timed how long it took them to complete it. To expose the fish to microwaves she used a standard kitchen microwave. Experiment 1 She began the experiment with 30 fish which she broke into 3 groups of 10 fish each. The first week she gave all of the fish in every group the same type, brand, and amount of food. None of this food was microwaved. At the end of the week, she had all the fish swim through the maze and recorded the average time for each group to complete it. Experiment 2 The next week she gave one group of 10 fish food that had been microwaved for 10 seconds, one group of fish food that had been microwaved for 20 seconds, and one group food that had not been microwaved at all. She used the same type, brand, and amount of food as she did the first week. After the second week she had the fish swim through the maze and recorded the average time for each group to complete it. The scientist then compared the averages from the first week to the averages of the second week. 1. Which of the following served as the control group in this experiment? a. The fish that received no food. b. The fish that received the food microwaved for 10 seconds. c. The fish that received the food microwaved for 20 seconds. d. The fish that received the food that had not been microwaved. 2. Which of the following variables would NOT need to be controlled in the experiment? a. The type of fish used. b. The type of microwave used. c. The amount of time the food was in the microwave. d. The type of food used. 3. Which of the following would NOT be a possible hypothesis for this experiment? a. The more microwaves the fish are exposed to, the smarter the fish will become. b. The warmer the food given to the fish, the smarter the fish will become. c. The fewer microwaves the fish are exposed to, the smarter the fish will become. d. The less microwaves the fish are exposed to, the faster they will complete the maze. 4. Which of the following best explains the purpose of the maze? a. To make sure the fish had a challenge after being exposed to microwaves. b. To see which fish could swim faster. c. To have a consistent measure for the amount of radiation the fish was exposed to. d. To have a consistent measure for the smartness of the fish.

5 5. Which of the following charts would best support the hypothesis that the more microwaves the fish are exposed to, the smarter they are? a. b. Finish Maze Week 1 (sec) Amount of Time Food Was Microwaved Week 2 (sec) Finish Maze Week 2 (sec) Finish Maze Week 1 (sec) Amount of Time Food Was Microwaved Week 2 (sec) Finish Maze Week 2 (sec) c. d. Finish Maze Week 1 (sec) Amount of Time Food Was Microwaved Week 2 (sec) Finish Maze Week 2 (sec) Finish Maze Week 1 (sec) Amount of Time Food Was Microwaved Week 2 (sec) Finish Maze Week 2 (sec)

6 Students in an introductory chemistry class studied the effects of temperature, liquid volume, and surface area on the volume of CO2 gas released and the reaction time when two antacid tablets are dropped into water. Experiment 1 Five Erlenmeyer flasks filled with exactly 50 ml of water were prepared for the experiment. Each flask was heated to a different temperature just before the experiment. Students crushed two antacid tablets and simultaneously poured the powder into the water while sealing the mouth of the flask with a standard size balloon and starting the stopwatch. As the antacid reacted with the water, the CO2 gas released inflated the balloon. When the reaction rate slowed enough that the balloon was no longer inflating, students measured the circumference of the balloon and recorded their results. Their data is given in Table 1. Water Volume (ml) Table 2 CO2 Gas Released Based on Balloon Circumference (cm) Reaction Time (sec) Table 1 Initial Water Temperature ( C) CO2 Gas Released Based on Balloon Circumference (cm) Reaction Time (sec) Experiment 3 A similar procedure as that used in Experiment 1 was followed for the third experiment. While the initial temperature of the water was kept at 27 C and the volume of water placed in the flasks was 50 ml, the size of the two antacid tablets was altered in each trial. Students again measured the circumference of the CO2 gas filled balloon and measured the reaction time using a stopwatch. Their data is given in Table 3. Table 3 Experiment 2 A similar procedure as that used in Experiment 1 was followed for the second experiment. While the initial temperature of the water was kept at 27 C, the volume of water in the Erlenmeyer flasks was modified for each trial. Five different water volumes were used. Students again measured the circumference of the CO2 gas filled balloon and measured the reaction time using a stopwatch. Their data is given in Table 2. Antacid Tablet Size CO2 Gas Released Based on Balloon Circumference (cm) Reaction Time (sec) Whole tablet Cut in half Cut in quarters Crushed into powder

7 1. Which of the following experiments should a scientist try in order to speed up the reaction as fast as possible? A. 29 C, 50mL of water, whole tablet B. 29 C, 50mL of water, crushed tablet C. 49 C, 50mL of water, whole tablet D. 49 C, 50mL of water, crushed tablet 2. If a scientist wanted to produce the least amount of CO2 gas possible, which of the following conditions would produce this result? A. 27 C, 50mL of water, tablet cut into quarters B. 27 C, 50mL of water, crushed tablet C. 27 C, 150mL of water, tablet cut into quarters D. 27 C, 150mL of water, crushed tablet 3. If a scientist wanted to test the effect of pressure on the amount of CO2 gas formed, which changes would be necessary in the procedure of Experiment 1? A. The antacid tablets should be cut in half instead of crushed while temperature is kept constant. B. Different volumes of water should be used in each flask while temperature is kept constant. C. The flasks should be put under different pressures while temperature is kept constant. D. Both pressure and temperature should be different in each flask. 4. A scientist wants to have the reaction happen as slow as possible. Which conditions would allow her to do that? A. 27 C, 50mL of water, whole tablet B. 27 C, 50mL of water, crushed tablet C. 27 C, 150mL of water, whole tablet D. 27 C, 150mL of water, crushed tablet

8 Two groups of students, attending different schools in the same town became concerned about the sanitation of their school s cafeteria. To do some investigation each group swabbed various surfaces their food comes in contact with. The students collected the swabs in sterile test tubes and returned to their lab classrooms where they poured warm nutrient agar into several Petri dishes. Using inoculation loops and Bunsen burners, the students streaked the plates with the sterile swaps transferring the samples collected onto their Petri dishes and streaking the plates in a fashion modeled by their teacher. Additional Petri dishes were streaked with sterile swabs not used to collect samples around the school. The Petri dishes were taped shut to reduce the chance of cross contamination and placed inside an incubator at 37 C for a period of two days. When the students returned to their lab, they retrieved the Petri dishes and counted the number of colonies that were evident in the Petri dish. The results are given in the tables below. Surface Table 1 Cultures Grown from Food Management Areas in School 1 (2 Days) (4 days) (1 Week) Food Tray 7 35% 15 52% 30 Dry Food Shelf 5 27% 12 46% 22 Countertop Surface 8 39% 24 73% 49 Refrigerator 4 19% 10 42% 22 Surface Table 2 Cultures Grown from Food Management Areas in School 2 (2 Days) (4 days) (1 Week) Food Tray 8 47% 18 75% 35 Dry Food Shelf 3 19% 9 25% 19 Countertop Surface 9 50% 29 82% 55 Refrigerator 6 25% 30 58% 35 Control # (2 Days) Table 3 Cultures Grown from Control (4 days) (1 Week) School 1a 2 5% 3 8% 4 School 1b 1 2% 3 5% 7 School 2a 0 0% 1 2% 4 School 2b 2 6% 3 8% 5

9 1. Which of the following statements is best supported by the data? a. Food trays have the largest quantity of bacterial colonies. b. Dry Food storage has the fewest bacterial colonies. c. Countertop surface is the least sanitary. d. Refrigerators have the largest percentage of bacterial plaques. 2. Which of the following generalizations is consistent with the experimental results in Table 1 and Table 2? a. The students at school number one contaminated the countertop before collecting a sample. b. School number one is more sanitary than school number two. c. School number one is less sanitary than school number two. d. Both school schools are equally unsanitary. 3. Which of the following explains why the bacteria cultures were counted after 2 days, 4 days, and 1 week? a. The students did not have school and the other days and were unable to check the cultures. b. The days checked were being kept as a control in the experiment. c. The days were only changed when necessary d. Keeping the number of days the same for both experiments makes the results less accurate. 4. Under which of the following conditions would the experiment in the schools be best conducted? a. In Illinois, where the science classrooms are the best in the country b. In a sterile lab room that contains no bacteria. c. In a natural classroom where the students will feel most comfortable. d. In a hospital where other bacteria are available. 5. Which of the following explains why both groups of students tested the same locations in the Food Management Areas (food tray, dry food shelf, countertop surface, and refrigerator)? a. The students at the second school lacked the originality to think of different locations. b. The students tested the same locations so that it would be easy to compare data. c. The students at the first school found the best locations to test and the second school wanted to do the same. d. The two schools chose the same locations by coincidence. 6. Which of the following lab procedures could change the accuracy of the results the students found? a. If the students used a clean swab for each sample, the samples would become contaminated. b. If the students used the same swab repeatedly without sterilizing it, the samples would become contaminated. c. If the students used streaking loops that had been sterilized twice before using them, the samples would become contaminated. d. If the students collected more control samples, the samples could become contaminated. 7. The control group data is most likely a. the average of the data from on swab of each surface. b. the average of the data from the two schools. c. the sterile swabs that were used to streak additional petri dishes. d. swabs that were taking from parts of the school that do not have food.