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Try our free ACT Science practice tests. All of our practice questions include answers and detailed explanations. Get started with your ACT Science prep right now! Directions: The passage below is followed by several questions. After reading the passage, choose the best answer to each ACT Science practice question. You may refer to the passage as often as necessary. Calculators may NOT be used on this test.
Passage I Eutrophication is a phenomenon where excessive amounts of nutrients are added to a marine ecosystem. These nutrients cause plant life like algae to multiply rapidly, leading to very high population densities. In freshwater ecosystems, the algae can become so dense that it can turn ponds, lakes or even smaller rivers green. The algae grows to an unreasonable level at a very fast rate. The algae are known as phytoplankton and are microscopic, single-celled organisms. A body of water that is experiencing eutrophication and a resulting bloom can be quickly devastated. Eutrophication affects all living organisms in the area including fish, birds and mammals. The top layer of phytoplankton causes such a build-up on the surface that they accumulate sediment. When this occurs the sunlight is blocked and it will choke off the plant life below the surface. The phytoplankton will also cause less surface area for the water to interface with air. As a result, there will be less oxygen available in the water. As oxygen continues to deplete, the depletion can have a negative effect on life as there will be less oxygen to support the organisms below the surface that depend on the oxygen from plants that diffuses into the water. Scientist 1 Scientist 2 Next Practice Tests: More Practice Tests: act.org,actprofile.org,act.org,actstudent.org,act.alertline.com,services.actstudent.org,career4.successfactors.com,engage.act.org,discoveractaspire.org,qc.vantage.com,myworkkeys.act.org,twitter.com,facebook.com,youtube.com,plus.google.com,linkedin.com,preview.act.org,workreadycommunities.org,pearson.com,instagram.com,actaspire.org,run2.careerready101.com,run2.keytrain.com,leadershipblog.act.org
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An actual ACT Science Test contains 40 questions to be answered in 35 minutes.
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ACT Science Practice Test 1 (40 questions) with Answers and Explanation. You can download Full ACT Science Practice Test PDF in a printable and editable file for free. Prepare your ACT Science final exam test. ACT Science Practice Test 1
The passages in this test are followed by several questions. After reading each passage, choose the best answer to each question. You may refer back to the passages as often as necessary. You are not permitted to use a calculator on this test. ACT Science Passage I—Data RepresentationThe earth’s gravitational force produces a downward acceleration of 9.8 m/s2 on all objects near the earth’s surface. Other forces, including those produced by wind and aerodynamic lift, as well as jet, rocket, internal combustion or other engines may also exert upward or downward forces on these objects. These other forces, acting in combination with gravity, can cause a net force greater than or less than gravity, and, therefore, a net acceleration different from the downward acceleration of 9.8 m/s2 caused by gravity. Table 1 and Figure 1 provide information about the vertical velocities measured for three different objects without regard to the horizontal motion of the objects. Each of the objects is operating under the influence of gravity for the entire 45 seconds being studied. They each may also be influenced by other vertical forces for all or part of that period. Where other forces have been applied, they always begin and end at one of the 5-second intervals. Table 1 indicates the vertical velocities of the three different objects as measured every 5 seconds. Positive velocities indicate motion upward, and negative velocities indicate motion downward. Figure 1 is a graphical representation of the velocity of each object at every point during the 45 seconds under review. 1. Which of the three objects may be traveling solely under the influence of gravity for the entire period shown?
Answer: D 2. For the time period shown, which of the three objects is/are traveling solely under the influence of gravity for at least part of the 45-second period?
Answer: B 3. For second 5 through second 25, which of the objects is/are moving with constant acceleration?
Answer: D 4. Which answer best describes the motion of object 1?
Answer: A A positive change in the direction of the line on the graph indicates a positive change in velocity. If the line is below zero, this means that the object moves downward but at decreasing speed. If the line is moving upward above zero, this means the object is moving upward at an increasing speed. Only answer choices A and B state that the object is traveling downward at second 0. This is correct because the graph line begins at –100. Figure 1 indicates that the object reaches zero velocity at approximately 10 seconds. Changing from negative to positive velocity means it changes direction from downward to upward. Table 1 indicates that that point is a bit before second 10 since it is already traveling upward at 2 m/s by second 10. We can calculate that the change in direction occurs at 9.8 seconds. Answer choice A correctly states that the object’s speed decreases after second 30 as indicated by the downward slope in Figure 1 and the decreasing numbers in Table 1. Answer choice c, which is correct until that point, incorrectly states that the object’s speed continues to increase. 5. From second 15 to second 35 the velocity of object 2 undergoes only very small changes. What is the best explanation for this?
Answer: C Answer choice A is incorrect because object 2 has not leveled off. Its velocity has nearly leveled off, but it is still falling at nearly 100 m/s. Answer choice D is incorrect because the changes in gravitational force due to even the most extreme terrain changes are far too small to produce the result described. ACT Science Passage II—Research SummaryTitration is a method used to measure the concentration level of a given substance in a solution. A solution of known concentration, called the titrant, is slowly added, in measured amounts, to the solution being titrated. The titrant must contain a substance that reacts with the titrated solution, and the reaction must be measurable. Once the two substances have fully reacted, we know the mass of the titrant used The reaction of hydrochloric acid (HCl) and sodium hydroxide (NaOH), a strong base, is represented as HCl + NaOH → H2O + NaCl. This experimental series involves three trials. Each uses a sodium hydroxide solution at 0.2 M concentration as the titrant. The solution to be titrated is precisely 20 ml of hydrochloric acid solution at a concentration between 0.1 M and 0.3 M. (A 1.0 M concentration means 1.0 mole/1.0 liters of water.) The resulting products, water and sodium chloride, are acid neutral. When pH 7.0 (acid neutrality) is reached, Table 1 shows the pH values after each addition of 2 ml of the titrant, up to 30 ml, for each of the three trials. Tables 2, 3, and 4 show a detailed view of what happens to the pH levels in the vicinity of pH 7.0 as titrant is added. 6. Based on the formula for the reaction between hydrochloric acid and sodium hydroxide, how many moles of sodium hydroxide are required to fully react with one mole of hydrochloric acid? Answer: C 7. The molar mass of HCl is 36.5 grams and the molar mass of NaOH is 40.0 grams. How many grams of HCl must be dissolved in a 20 ml solution to bring it to a concentration of 0.1 M?
Answer: B 8. Based on Tables 2, 3, and 4, what is the best estimate that can be made of how many ml of the NaOH titrant it took to neutralize the HCl solutions used in trials 1, 2, and 3?
Answer: D 9. How many ml of titrant were used in the trials?
Answer: A 10. What substances should we expect to discover in the titrated solution at the end of the trials?
Answer: C 11. How should the mass of HCl in the titrated solution be calculated?
Answer: B ACT Science Passage III—Conflicting ViewpointsA geneticist and a physiologist each explained what causes the wide variety of different height profiles found among different countries and ethnic groups on the planet. The geneticist pointed to data such as that represented by Figure 1. Each curve shows the reported distribution of the specified adult population over the spectrum of heights. One represents an estimate of global averages, and the other two are estimates for two countries. He argued that the distinctive height profile of each separate population grouping supported the hypothesis that height is determined by The physiologist said there were significant differences between the global profile and those of the two countries in terms of nutritional and other health-related factors. She also pointed to estimated historical data. Table 1 and the bar chart in Figure 2 present an image of long-term trends in typical height. She argued that if genetics determined the height, no such change would occur. 12. Based on Figure 1, what is a typical height in country A?
Answer: C 13. Based on Figure 1, what is the most typical height in country B?
Answer: A 14. What is the best description of the relationship between the shapes of the three curves shown in Figure 1?
Answer: C 15. Which statement is supported by Table 1 and Figure 2 but not supported by Figure 1?
Answer: B 16. Which is the most complete statement about country B supported by Table 1 and Figure 2?
Answer: A 17. Which statement about country A is supported by Table 1 and Figure 2?
Answer: D 18. What hypothesis is supported by a comparison of the three curves in Figure 1?
Answer: C ACT Reading Passage IV—Research SummaryNASA is operating the satellite-based Solar Radiation and Climate Experiment (SORCE). Its purpose is to improve our understanding of the nature, including changes in quality and intensity, of solar radiation reaching our planet, by continuously monitoring the intensity of solar radiation by time and by frequency. Five different instruments are mounted in the satellite to achieve coverage of the desired spectrum range. Table 1 shows the instruments used and the wavelength (λ) range monitored by each. Figure 1 illustrates how they are arranged in the satellite. Table 2 names the major categories of electromagnetic radiation and shows the frequency range included in each. Experiment 1 The Total Irradiance Monitor (TIM) monitors the total solar irradiance (TSI) over the entire electromagnetic spectrum. Figure 2 shows the average daily TSI, measured in watts/meter2 (W/m2) as measured by the TIM for December 20 through 26, 2010. Experiment 2 The other instruments measure irradiance by wavelength. This measure is called solar spectral irradiance (SSI). Figure 3 shows the SSI for December 24, 2010, in watts/meter2/nanometer (W/m2/nm). This is a measure of the intensity of solar irradiance by wavelength. 19. Based on Tables 1 and 2, which types of electromagnetic radiation are measured in the SORCE experiment by instruments other than the TIM?
Answer: B The SIM covers part of the ultraviolet, visible light, and infrared spectrums. SOLSTICE A and B each cover part of the ultraviolet range. XPS begins at 1 nm, which is the upper end of the x-ray range, and extends into the ultraviolet range. 20. According to Table 2 and Figure 3, what is the difference between the lowest and the highest daily average of total solar irradiance (TSI)?
Answer: A 21. Approximately what proportion of the average daily solar irradiance is the difference between the week’s highest level and its lowest level?
Answer: D 22. Based on Figure 3, which wavelength transmitted the highest level of solar irradiance?
Answer: C 23. What best describes the difference between total solar irradiance (TSI) and solar spectral irradiance (SSI)?
Answer: B 24. Based on Figure 3 and Table 1, which type of electromagnetic radiation carries the most solar irradiance?
Answer: B 25. Refer again to Figure 3. After visible light, which type of electromagnetic radiation carries the most solar irradiance?
Answer: C ACT Science Passage V—Research SummaryMicrobe populations, including those of disease-producing bacteria, can change their characteristics over relatively short periods of time. A series of experiments involving pneumococci were conducted to determine whether and how these changes take place. In all three of the experiments described here, measures were taken to protect against contamination from other bacteria throughout the course of the Experiment 1 Experiment 2 First, samples were taken from a patient who was initially analyzed to be infected only with type I pneumococci. Cultures were grown from these samples in three ways and analyzed. The first was simply to grow bacterial colonies from the sample in petri dishes. The second was to examine what happened when the same bacteria infected others. Mouse A was inoculated with untreated infected material. Then mouse B was inoculated with type I serum, which kills type I bacteria, and with the infected material from the patient. Table 2 reports those results. (Note: each day a different mouse B and mouse A were used.) Experiment 3 In each case, a mouse was inoculated with R bacteria from the colony. The mice either died after between 2 and 12 days or survived indefinitely. The blood of each deceased mouse was then cultured and tested for pneumococci that were examined to determine whether they were R or S bacteria. Table 3 reports the results. 26. Consider the results reported in Table 2. Which of the following statements about the samples taken directly from the patient and culture is correct and important for the study?
Answer: B 27. Based on the overall findings reported by Table 2, which of the following answers is most correct?
Answer: D 28. From the standpoint of understanding how bacterial strains change over time, what is the most interesting thing about the results reported in Table 3?
Answer: D 29. Which answer is the most important statement supported by the data reported from the three experiments?
Answer: B 30. Which statement is best supported by the data in Table 2, viewed in conjunction with the other data?
Answer: B ACT Science Passage VI—Data RepresentationVariations in the proportion of the two major isotopes of oxygen, 18O and 16O, in seawater or landbased water, including glacial ice, are believed to be a proxy for changes in temperature. 16O is lighter than 18O, so it evaporates first from seawater. This leaves a higher concentration of 18O in seawater and a lower concentration in the evaporated water, which then falls to Earth as precipitation. If the falling water freezes, glaciers are formed, which trap the low 18O precipitated water. In glacial periods, oceans are richer in 18O, but in interglacial periods the glaciers melt and 16O-rich water flows back into the oceans. For this reason high 18O concentrations in seawater are believed to be an indication of cold climate periods in which glaciers are built up. The measure of how far above normal the concentration of 18O in a sample it is called δ18O. It is computed as follows: Thus high δ18O means more 18O and less 16O than normal. Low δ18O is the reverse. Figure 1 illustrates the δ18O cycle from seawater Low δ18O water evaporates from the ocean, leaving higher δ18O water behind. The evaporated water falls as precipitation, forming low δ18O glaciers. In interglacial periods, the glaciers melt, and 16O flows back into the ocean, reducing δ18O there. Figure 2 is a simplified representation of the changes in seawater δ18O for the past 2,000,000 years. The high δ18O periods are when 16O evaporates from the seawater and is frozen into glaciers. The low δ18O periods are when the glaciers melt and return the 16O to the seawater. 31. Based on Figure 2 and the relationship between δ18O, glaciation, and climate, how long ago was the period with the coldest temperatures and the most glaciation?
Answer: C 32. Based on Figure 2 and the relationship between δ18O and the return of melted glaciers to the ocean, how long ago would sea levels have been highest?
Answer: D 33. Referring to Figure 2, how many periods of glacial buildup occurred between 0.25 and 0.50 million years ago?
Answer: A 34. Based on Figure 2, what is the highest number of glacial melting periods to occur within one 0.25-million-year span?
Answer: D 35. During what period shown on Figure 2 were the temperature swings between glacial buildups and glacial melts consistently the most mild over an extended period of time?
Answer: B ACT Science Passage VII—Data RepresentationValency is a concept in chemistry that provides rules for determining which chemical elements can combine in what proportions to form compound substances. Protons and neutrons together form the nucleus at the center of an atom. The much lighter electrons whirl around the nucleus in what are called shells, rings, orbits, or energy levels. The left-hand diagram in Figure 1 is a representation of this structure. At right in Figure 1 is a representation of valency. Each electron ring has a normal electron capacity. The first ring’s capacity is two electrons. The other rings each have a capacity of eight electrons. Atoms tend to bring their outer rings to capacity through some kind of collaboration or exchange with other atoms. The valency of an atom is the number of surplus or deficit electrons in its outer ring. Ionic bonding involves a combination of atoms having only one or two electrons in their outer rings with others that need only one or two electrons to complete their outer rings. The first type empty their incomplete outer rings by lending out their outer-ring electrons, and the second type borrow them to complete their outer rings. This is called ionic bonding because the atoms become electrically charged ions. The attraction between the positive ions that give up their electrons and the negative ions that receive them helps to bind the resulting compound. Figure 2 shows how this works in the case of two common substances, H2O and NaCl, water and salt. Tables 1 and 2 show how each atom borrows or loans electrons either to complete or to empty its outer ring. 36. According to Tables 1 and 2, what is the resulting charge of each compound?
Answer: D 37. Refer to Tables 1 and 2 and Figure 1. When sodium (Na) is stripped of the one electron in its outer shell, what is its electrical charge? Answer: A 38. Based on Figure 2 and the explanations presented here, how many electron rings does a positive sodium ion have?
Answer: B 39. Based on the data presented here about ionic bonding, which element other than sodium would chlorine (Cl) be most likely to form an ionic bond with?
Answer: D 40. As shown in Figure 2 and Table 1, hydrogen and sodium each have only one electron in their outer rings. In light of the information presented here, what is the best explanation for why it takes one sodium atom to form a compound with one chlorine atom, but it takes two hydrogen atoms to form a compound with one oxygen atom?
Answer: C |