ACT Science Mastery Guide (2026)

Section Overview

The ACT Science section is the fourth section of the ACT. You have 35 minutes to answer 40 questions across 6–7 data sets. Each data set is followed by 5–7 questions. The section covers a range of scientific topics: biology, chemistry, physics, earth science, and space science.

The Big Secret: This Is Not a Science Test

This is the single most important thing to understand about the ACT Science section: you are not being tested on your knowledge of biology, chemistry, or physics. You are being tested on your ability to read, interpret, and reason about data presented in the form of tables, graphs, and experimental descriptions.

Nearly every question can be answered correctly with zero prior science knowledge by reading the data carefully. In fact, students who apply their science knowledge instead of reading the data often choose wrong answers — because the passage may describe a simplified model or a hypothetical scenario that does not match real-world science.

The one exception: a small number of questions (~3–5 per section) require basic scientific knowledge — understanding that photosynthesis produces oxygen, or that pH below 7 is acidic. But these are rare and involve only fundamental concepts, not specialized knowledge.

The 3 Data Formats

Data Representation

Data Representation passages are the most straightforward. They present 1–3 figures (graphs, tables, or charts) with a short introductory paragraph defining key terms. Questions ask you to read values from the figures, identify trends, and make simple inferences from the data.

What to do

• Read the intro paragraph: It defines variables and the experimental setup in 2–4 sentences. Do not skip it.
• Check all figure labels before reading questions: x-axis label, y-axis label, units, and legend (if present).
• Go directly to the figure for each question: Most questions ask you to find or compare specific data points — go look at the figure, not the text.
• For trend questions: Is the relationship increasing, decreasing, or nonlinear? Note the direction of the curve or data pattern.

Common question types

• "According to Figure 1, at [x value], what is the value of [y variable]?" → Locate x on the axis, read the y value.
• "Which of the following best describes the relationship between [variable 1] and [variable 2]?" → Identify the trend from the graph.
• "Based on Tables 1 and 2, which [condition] produced the highest [measurement]?" → Compare across tables.

Research Summaries

Research Summaries passages describe 2–3 experiments conducted by scientists to investigate the same question. Each experiment varies one or more conditions and measures a result. Questions ask about experimental design, results, and comparisons across experiments.

How to read Research Summaries

• Read the introduction: Understand what overall phenomenon is being investigated.
• For each experiment, identify: What was changed (independent variable), what was measured (dependent variable), and what was kept constant (control variables).
• Do not memorize every number: Skim to understand the structure. Return to the data for each specific question.

Common question types

• "Which experiment tested the effect of [variable] on [outcome]?" → Identify which experiment varied that specific variable.
• "Based on the results of Experiment 2, as [variable A] increased, [variable B]…" → Read Experiment 2's data.
• "The experimental design of Experiment 3 was most similar to which other experiment?" → Compare procedures across experiments.
• "Suppose a scientist conducted Experiment 1 with [modified condition]. Based on the results, what would likely happen?" → Extrapolate the established trend.

Conflicting Viewpoints

The Conflicting Viewpoints passage always appears last in the section. It presents 2–3 different scientific explanations or theories for the same phenomenon, each presented separately. Unlike the other formats, there are usually no graphs or tables — the information is in the text.

This passage takes the most time (~8–10 minutes) and requires the most careful reading. Budget for it explicitly.

How to approach Conflicting Viewpoints

• Read each viewpoint carefully and separately. Identify: What does Scientist 1 claim? What evidence do they give? What does Scientist 2 claim? Where do they agree or disagree?
• Do not try to decide which scientist is "right." The ACT does not ask you to judge — it asks you to accurately represent each viewpoint.
• Make a quick note (on scratch paper): S1 claims X because Y; S2 claims A because B.
• When answering comparison questions: Re-read the relevant part of each viewpoint before choosing an answer — do not rely on memory.

Common question types

• "Which scientist would agree with the statement that [X]?" → Find the statement in each scientist's viewpoint.
• "Scientist 1's view differs from Scientist 2's view in that Scientist 1 believes…" → Identify the point of disagreement.
• "Both Scientist 1 and Scientist 2 would most likely agree that…" → Find a claim made (or implied) by both.
• "New evidence shows [X]. This would most support which scientist?" → Determine which viewpoint is consistent with the new evidence.

Graph & Table Reading Skills

Reading graphs and tables quickly and accurately is the core skill of ACT Science. Before you can answer any question, you must understand what you are looking at.

Step-by-step for any figure

Types of figures you will see

• Line graphs: Show how a variable changes continuously. Look for maximum/minimum, slope direction, and where lines intersect.
• Bar graphs: Compare discrete categories. Look for tallest/shortest bar and relative heights.
• Scatter plots: Show correlation between two variables. Identify positive correlation (both increase), negative correlation (one increases as other decreases), or no correlation.
• Data tables: Read column headers and row labels before reading any numbers. Find the specific row/column combination the question asks about.

Scientific Notation & Units

ACT Science data often uses scientific notation (e.g., 3.2 × 10⁻⁵) and metric unit prefixes. You do not need to do complex calculations — but you must be able to compare values and identify which is larger or smaller.

Key metric prefixes

Comparing values in scientific notation

Compare exponents first: 3.2 × 10⁻³ > 5.8 × 10⁻⁵ because –3 > –5. When exponents are equal, compare the coefficient (the number before ×10ⁿ). The ACT will ask you to identify which trial produced the "highest" or "lowest" value — you often just need to compare the exponents.

Interpolation vs Extrapolation

Some ACT Science questions ask you to predict a value at a point not shown directly on the graph. Understanding whether you are interpolating or extrapolating affects how confident you can be in your answer — and the ACT sometimes asks you to distinguish between them.

When extrapolating, assume the established trend continues unless the question gives you reason to think otherwise. The ACT will sometimes ask: "If the experiment were extended to [higher value], which of the following would most likely occur?" — extend the trend you see in the graph.

Time Strategy

35 minutes ÷ 6–7 data sets = approximately 5 minutes per data set. Conflicting Viewpoints takes longer (~8 minutes). Here is how to distribute your time:

• Data Representation passages: 4–5 minutes each — these are the fastest; the data is visual and questions are direct
• Research Summaries: 5–6 minutes each — need to understand experimental structure; questions may compare across experiments
• Conflicting Viewpoints: 8–10 minutes — text-heavy, inference-heavy; budget extra time here
• Order tip: Some students skip Conflicting Viewpoints first, complete all other passages in ~25 minutes, then spend the remaining ~10 minutes on Conflicting Viewpoints
• Never leave blanks: With 2 minutes remaining, fill in an answer for every unanswered question

ACT Science Study Plan