Breakdown of the 40 Questions and 7 Passages
The ACT Science section consists of 40 multiple-choice questions spread across six or seven passages. While the exact number of passages can vary slightly between test dates, the total question count remains fixed. Each passage is followed by 5 to 7 questions that increase in complexity. The scoring is based on a raw score conversion; your total number of correct answers is mapped to a scaled score from 1 to 36. Because there is no penalty for guessing, leaving any bubble blank is a tactical error. The test is designed to be a marathon of focus, requiring you to transition rapidly between different scientific disciplines, such as meteorology, microbiology, and particle physics, without losing momentum.
The Three Passage Types: Data, Research, Viewpoints
Every ACT science passages set falls into one of three distinct categories. Data Representation passages (typically 2-3 per test) focus on graphic literacy, asking you to read values and identify trends. Research Summaries (typically 3 per test) describe one or more related experiments, requiring you to understand the experimental design and the impact of specific variables. Finally, the Conflicting Viewpoints passage (usually 1 per test) presents 2-7 different hypotheses regarding a specific scientific phenomenon. Understanding these types allows you to apply the correct cognitive framework immediately. Recognition of the passage type is the first step in prioritizing which questions to tackle first based on your personal strengths.
Time Management Strategies for the Section
Time management is the primary hurdle for most high-scoring candidates. To maximize efficiency, many students adopt a "questions-first" approach for Data Representation and Research Summaries, referring back to the text only when a specific detail is required. This prevents over-investing time in complex jargon that may not even be tested. However, the Conflicting Viewpoints passage requires a more thorough initial read to grasp the nuances of each argument. A common strategy is to save the Viewpoints passage for last, as it is the most time-consuming. By hitting a target pace of 5 minutes per passage for Data/Research and 7 minutes for Viewpoints, you can ensure you reach the final question without rushing.
Data Representation Passages: Mastering Graphs and Tables
Interpreting Trends in Line and Bar Graphs
ACT science graphs are the backbone of the Data Representation section. You must be able to identify direct variation, where two variables increase together, and inverse variation, where one increases as the other decreases. Questions often ask you to perform an extrapolation, which involves predicting a value beyond the range of the provided data points, or an interpolation, which is estimating a value between two known points. Pay close attention to the axes; the ACT frequently uses different scales or units (e.g., millimeters vs. centimeters) to catch inattentive testers. If a line has a steep positive slope, the rate of change is high, whereas a flat line indicates that the independent variable has no effect on the outcome.
When dealing with ACT data representation in tabular form, the sheer volume of numbers can be overwhelming. The key is to use the question as a filter. If a question mentions "Experiment 2, Table 1, at 30°C," your eyes should move exclusively to that intersection. Tables often contain multiple columns representing different trials or conditions. You must differentiate between a constant and a variable within these rows. Often, the ACT includes "distractor" data—columns of information that are completely irrelevant to the specific question being asked. Developing the discipline to ignore extraneous digits is essential for maintaining speed and accuracy during the 35-minute window.
Identifying Relationships Between Variables
Questions in this section frequently ask you to determine how one variable responds to changes in another. This requires a firm grasp of correlational logic. For instance, if a table shows that as the concentration of a solute increases, the boiling point of the solution also increases, you have identified a positive correlation. You might be asked to select a graph that best represents this relationship. On more difficult questions, you may need to synthesize information from two different figures. This "cross-referencing" requires you to find a common variable that links Figure 1 to Figure 2, effectively acting as a bridge to reach the correct conclusion.
Research Summaries Passages: Analyzing Experiments
Identifying the Purpose and Hypothesis
In research summaries ACT sections, the introductory paragraph usually contains the "why" of the experiment. The hypothesis is the proposed explanation or prediction that the scientists are testing. Understanding the objective is crucial because the questions will often ask how a change in the results would affect the validity of the original theory. If the goal is to determine how light intensity affects plant growth, every part of the experimental setup—from the wattage of the bulbs to the height of the stems—revolves around that central inquiry. Identifying the hypothesis early helps you contextualize the data points that follow in the subsequent tables.
Understanding Independent vs. Dependent Variables
Distinguishing between variables is a fundamental skill in experimental analysis. The independent variable is the factor that the researcher deliberately manipulates (often plotted on the x-axis), while the dependent variable is the factor that is measured or observed in response (plotted on the y-axis). For example, in a study on enzyme activity, the pH level might be the independent variable, while the reaction rate is the dependent variable. Many ACT questions test your ability to identify which variable was held constant across different trials. Misidentifying these roles can lead to choosing the exact opposite of the correct answer, especially in questions regarding the relationship between experimental components.
Evaluating Experimental Design and Controls
A critical component of the scientific method is the use of a control group, which serves as a baseline for comparison. The ACT often asks what would happen if a certain step in the procedure were omitted or changed. You must evaluate whether an experiment is well-designed to test its stated hypothesis. This might involve identifying a confounding variable—an uncontrolled factor that could influence the results. For instance, if a study compares the growth of two different species of bacteria but keeps them at different temperatures, the temperature becomes a confounding variable that makes the results difficult to interpret. Recognizing these design flaws is a hallmark of an advanced scorer.
Conflicting Viewpoints Passages: Comparing Hypotheses
Mapping Out Each Scientist's Argument
The conflicting viewpoints ACT passage is essentially a reading comprehension test in a scientific context. You are presented with multiple perspectives (e.g., Scientist 1, Scientist 2, or Theory A, Theory B) on a single phenomenon, such as the extinction of dinosaurs or the composition of a planet's core. The most effective strategy is to briefly jot down the "main idea" for each viewpoint. What is their primary claim? What is the mechanism they propose? By summarizing each position in three or four words, you create a mental map that prevents you from confusing the competing theories when the questions begin to ask for specific comparisons.
Finding Points of Agreement and Disagreement
ACT questions often target the intersection of the two viewpoints. You might be asked, "Both Scientist 1 and Scientist 2 would likely agree that..." or "Scientist 1's model differs from Scientist 2's model in that..." These questions require you to look past the technical jargon to find the underlying logic. Often, the disagreement isn't about the data itself, but about the interpretation of that data. For example, both scientists might agree that a certain rock layer contains iridium, but one argues it came from a meteor while the other argues it came from volcanic activity. Identifying these specific points of contention is the quickest way to eliminate incorrect answer choices.
Using Evidence to Support or Weaken a Viewpoint
The most difficult questions in this section ask you to predict how new information would impact the existing theories. If a new study finds that the iridium layer is actually much older than previously thought, which scientist's argument is strengthened, and which is weakened? This requires an understanding of causal reasoning. To answer these, you must first identify the evidence each scientist relies on. If Scientist 1's argument depends on a specific timeline, any evidence disrupting that timeline directly weakens their position. This level of analysis goes beyond simple fact-finding and requires a holistic understanding of how evidence functions within a scientific argument.
Essential Foundational Science Concepts
Biology Basics: Cells, Genetics, Ecology
While the test focuses on reasoning, there is a baseline of science content on ACT that is assumed. In biology, you should understand the basic functions of organelles, such as the mitochondria (energy production) and ribosomes (protein synthesis). Familiarity with the basics of DNA and genetics, including terms like genotype, phenotype, and dominant vs. recessive traits, is essential. In ecology, you should understand the roles of producers, consumers, and decomposers within a food web. Knowing that photosynthesis consumes CO2 and produces Oxygen, while cellular respiration does the opposite, can save you precious seconds that would otherwise be spent trying to decipher a passage's introductory text.
Chemistry Fundamentals: Elements, Bonds, Reactions
Chemistry questions on the ACT often revolve around the properties of matter and the nature of chemical changes. You should be familiar with the Periodic Table, specifically the difference between atomic number and atomic mass. Knowing that the pH scale runs from 0 to 14 (with values below 7 being acidic and above 7 being basic) is a frequent requirement. You should also understand basic phase changes—melting, freezing, evaporation, and condensation—and how they relate to temperature and pressure. While you won't need to balance complex equations from memory, understanding that mass is conserved in a chemical reaction is a fundamental principle that the test frequently utilizes.
Physics Principles: Motion, Forces, Energy
Physics-related passages typically deal with mechanics, electricity, and thermodynamics. You should have a conceptual understanding of Kinetic Energy (energy of motion) and Potential Energy (stored energy), and how they can be converted back and forth. Basic laws of motion, such as the idea that an object in motion stays in motion unless acted upon by a force (Inertia), are often the hidden logic behind physics data. Understanding the relationship between density, mass, and volume ($D = M/V$) is also common. The ACT will provide specific formulas if they are complex, but knowing these foundational relationships allows you to interpret the variables in those formulas much more effectively.
Scientific Method and Reasoning Skills Tested
Making Predictions Based on Data
A common question format on the ACT asks what would happen if a researcher performed a "Trial 4" or added a new sample with a specific value. This requires you to look at the existing trend and extend it. If the temperature increased by 5 degrees in each of the first three trials, and the pressure increased by 10 units each time, you can safely predict that a further 5-degree increase will result in another 10-unit pressure jump. This is a test of linear interpolation. The ability to visualize the next data point in a sequence is a core reasoning skill that bypasses the need for high-level math, focusing instead on pattern recognition.
Drawing Logical Conclusions
Drawing a conclusion involves more than just reading a graph; it requires you to synthesize the results of an experiment with the initial hypothesis. You may be asked if the results "support" or "refute" a particular claim. This is where many students stumble by choosing an answer that is factually true according to the graph but does not actually address the question asked. A conclusion must be directly linked to the variables being tested. If an experiment only tested the effect of sunlight on tomato plants, you cannot draw a logical conclusion about the effect of sunlight on oak trees, even if the data shows a strong trend. This boundary of experimental scope is a frequent trap on the exam.
Identifying Strengths and Weaknesses in Studies
The ACT Science section often asks you to critique the methodology described in a passage. A "weakness" might be a small sample size, the lack of a control group, or the failure to account for an external variable like humidity or light. Conversely, a "strength" might be the use of multiple trials to ensure reproducibility. Understanding that a single trial is rarely enough to prove a hypothesis is a key part of scientific literacy. When you are asked why a scientist performed a certain step, the answer usually relates to increasing the accuracy of the measurements or isolating the independent variable to ensure a fair test.
Integrated Practice and Review Plan
Creating a Science Content Checklist
To ensure you are prepared for the small percentage of questions that require outside knowledge, create a checklist of high-yield topics. This should include the Scientific Method steps, basic cellular biology, the pH scale, and the laws of thermodynamics. While you shouldn't spend weeks studying these, a quick review of a "cheat sheet" can prevent you from missing easy points. Use your practice tests to identify recurring terms you don't recognize. If you see "osmosis" or "viscosity" mentioned in a way that assumes you know the definition, add those to your checklist. This targeted approach ensures your content knowledge is broad enough to support your reasoning skills.
Drilling by Passage Type
Not all science passages are created equal, and most students find one type significantly harder than the others. Use your ACT science reasoning practice sessions to identify your "weak" passage type. If you consistently struggle with the Conflicting Viewpoints passage, dedicate an entire afternoon to doing only those. By drilling a specific format, you become familiar with its unique traps and question patterns. For Data Representation, focus on speed; for Research Summaries, focus on identifying variables; for Conflicting Viewpoints, focus on the logic of the arguments. This modular training builds the stamina needed for the full 35-minute section.
Full-Length Science Section Practice
Finally, the Science section should never be practiced in isolation once you have mastered the basics. Because it is the final multiple-choice section of the ACT, you will be taking it when your mental energy is at its lowest. Practicing a full-length Science section after completing a full English, Math, and Reading section is the only way to simulate the testing fatigue you will experience on exam day. Analyze your mistakes not just for content errors, but for "fatigue errors"—misreading a graph or skipping a line of text. Building the endurance to stay sharp for those final 40 questions is often what separates a 30 from a 36.