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ACT Science Reasoning Reference Cheat Sheet
A printable reference covering data interpretation, experimental design, graph analysis, conflicting viewpoints, and timing strategies for grades 9-12.
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The ACT Science section tests how well students read graphs, compare experiments, evaluate evidence, and reason from scientific information. This cheat sheet helps students focus on the skills that appear most often instead of trying to memorize every science fact. It is useful for quick review before practice tests, class assessments, or ACT exam day. Students need it because the section rewards speed, careful reading, and evidence-based thinking. Core ideas include identifying variables, reading tables and axes, finding trends, and connecting claims to data. Important tools include slope = change in y / change in x, rate = change / time, and percent change = (new value - original value) / original value x 100%. Students should compare only one variable at a time when analyzing experiments. For conflicting viewpoints, the best answer is usually the one supported by the passage, not the one that sounds most familiar.
Key Facts
- Slope is calculated as slope = change in y / change in x, and it shows how quickly one variable changes compared with another.
- Rate is calculated as rate = change / time, and it describes how fast a process occurs.
- Percent change is calculated as percent change = (new value - original value) / original value x 100%.
- A direct relationship means both variables increase together or decrease together, while an inverse relationship means one variable increases as the other decreases.
- The independent variable is the factor the experimenter changes, and the dependent variable is the factor measured in response.
- A controlled variable is kept the same across trials so the experiment tests only the intended independent variable.
- On ACT Science questions, answer from the data in the passage first and use outside science knowledge only when the question clearly requires it.
- For timing, a common strategy is about 5 minutes per passage, with easier data and graph questions answered before longer reasoning questions.
Vocabulary
- Independent variable
- The factor that is deliberately changed in an experiment to test its effect.
- Dependent variable
- The factor that is measured or observed as the outcome of an experiment.
- Control group
- A comparison group that does not receive the tested treatment or condition.
- Trend
- A pattern in data, such as increasing, decreasing, leveling off, or changing at a steady rate.
- Extrapolation
- A prediction made beyond the range of the data shown.
- Conflicting viewpoints
- A passage type that presents different scientific explanations or claims for students to compare.
Common Mistakes to Avoid
- Ignoring axis labels and units is wrong because the same number can mean different things depending on scale, unit, or measured quantity.
- Assuming the graph starts at zero is wrong because many ACT graphs use shortened axes, which can make changes look larger or smaller than they are.
- Using outside knowledge instead of the passage is wrong when the question asks what the data or scientists state, because ACT answers must match the given evidence.
- Comparing two experiments that changed more than one variable is wrong because it can hide which variable actually caused the result.
- Reading only the first and last data points is wrong because the pattern may include a peak, dip, plateau, or reversal in the middle.
Practice Questions
- 1 A substance cools from 80°C to 50°C in 10 minutes. What is the cooling rate in °C per minute?
- 2 A plant grows from 12 cm to 18 cm. What is the percent increase in height?
- 3 A graph shows distance on the y-axis and time on the x-axis. If distance increases from 20 m to 60 m while time increases from 4 s to 12 s, what is the slope and what does it represent?
- 4 Two students explain the same data differently. What evidence should you compare first to decide which explanation is better supported?