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ACT Science: Deep Dive

A reading test in a lab coat: graphs, trends, and dueling scientists.

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What this covers

Every lesson is short enough to finish in one sitting and ends with questions that make you use what you just read.

  1. Reading Graphs and Tables FastAxes first, questions second, intro last5 min
  2. Trends, Interpolation, and ExtrapolationRead between the points, then beyond them5 min
  3. Experimental Design: Variables and ControlsWhat changed, what stayed, what it proves5 min
  4. Conflicting Viewpoints PassagesTwo scientists, one dataset, zero chemistry required5 min
  5. The Three Passage FormatsData representation, research summaries, conflicting viewpoints5 min
Show all 12 lessonsShow fewer lessons
  1. Experimental Design QuestionsVariables, controls, and what a change to the setup would do5 min
  2. Question First, Passage SecondThe triage habit that buys back four minutes7 min
  3. Questions That Need Two FiguresThe hardest common question type, made mechanical8 min
  4. The Arithmetic This Section Actually Asks ForSmall calculations, unit traps, and proportional reasoning7 min
  5. The Questions That Need Outside KnowledgeA small, predictable list worth knowing cold7 min
  6. Pacing Across the Whole SectionWhere the time actually goes, and how to spend it7 min
  7. Timed Set: Science Deep30 items, 15 minutes, real pacing30 min

A whole lesson, start to finish

Not a sample and not a summary. This is all of lesson 2, exactly as it reads in the app.

Lesson 2 of 12 · about 5 min

Trends, Interpolation, and Extrapolation

Read between the points, then beyond them

Three question verbs, one skill

A huge share of Science points comes from three moves. Identify the trend: as X increases, what does Y do? Interpolate: estimate a value between two measured points. Extrapolate: extend the pattern beyond the last measurement. All three start the same way, by stating the pattern in plain words before looking at any answer choice.

Key idea

Say the trend as a sentence: as pressure rises, volume falls. Direct relationships move together; inverse relationships move oppositely. Some data does neither, peaking in the middle or flattening at the ends, and the ACT loves those shapes precisely because as one increases, the other increases is wrong for them.

Interpolation is reading a value the table skipped. If 20 degrees gives 31 g and 30 degrees gives 39 g, then 25 degrees should give roughly 35 g, assuming the change between points is smooth. The ACT expects the assumption; answer choices are spaced so a rough midpoint estimate lands cleanly on one option.

Extending past the data

Extrapolation extends the pattern past the last point. If each 10-degree step added about 8 g across the whole table, the step from 40 to 50 degrees most likely adds about 8 more. Follow the established rate of change; do not invent a new one. If the steps were shrinking, keep shrinking them.

Remember

The safest extrapolation continues the most recent behavior of the data. A curve that rose steeply and then leveled off should be extended nearly flat, not steeply. Match the tail of the data, not its early slope and not your intuition about the phenomenon.

Careful

Science remains an optional section on the enhanced ACT, so budget your prep time deliberately. If your programs want it, trend questions are the highest-yield skill in the section. If none of your schools use it, these 40 minutes of test may not be worth adding to your test day at all.

Watch for the phrase varied directly versus varied inversely in answer choices, and translate before judging: directly means same direction, inversely means opposite directions. Then check the actual columns. A single row that breaks the pattern is enough to sink a claim that the relationship held across the entire experiment.

When a question asks which graph best represents the data in a table, sketch the trend arrow in your head first: rising, falling, rising-then-flat, peaked. Then match shapes. Deciding the shape before looking at the four thumbnails keeps the wrong graphs from arguing with you.

Now answer the question that follows it

This is one of 8 questions on that lesson. Pick an answer and it will tell you.

Table 1 shows gas volume at constant temperature: at 1 atm, 24 L; at 2 atm, 12 L; at 3 atm, 8 L; at 4 atm, 6 L. Question: Based on Table 1, the relationship between pressure and volume is best described as

Terms you will own

Cards come back on a schedule built from how well you knew them last time, so the ones you keep missing show up more.

More in deep dives: section by section

AEACT English: Deep DiveEvery grammar rule and rhetoric move the test can throw AMACT Math: Deep DiveFrom linear equations to trig, with backsolving as a weapon ARACT Reading: Deep DiveProve every answer from the passage, at speed

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