Most Frequently Tested ACT Science Topics

A lot of students get a little nervous when they see that the ACT has a science section. “But I’m not a science person!” they moan. But there’s a very important distinction between the topics on the ACT Science Test and any other science test you’ve ever taken. The most frequently tested ACT Science topics focus more on what you can do when given certain information, rather than what you know before coming into the test.

Though you need to be familiar with scientific terms to succeed on the ACT Science Test, the test’s topics also revolve around certain skills. In this post, we’ll look at the most frequently tested ACT Science topics so that you know what to expect on test day. (I’ll also point you in the right direction so that you can learn more about each topic and raise your score.)

The Scientific Method

The scientific method is the key underlying concept behind all science data found on the ACT.

Google Dictionary defines the scientific method as “a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.”

This widely accepted definition guides all valid scientific research. When carried out correctly, the scientific method yields useful, reliable results. Beyond the dictionary definition, the scientific method involves a number of procedural steps. In a nutshell, the steps are as follows:

  1. Observe some kind of scientific phenomenon.
  2. Describe what you’ve observed and the evidence of scientific facts you see. This description is called a hypothesis.
  3. Use the hypothesis to make predictions about what might happen under certain circumstances.
  4. Test those predictions by conducting science experiments to see if they’ll come true.
  5. If the results of the experiment challenge your hypothesis, repeat steps 2 through 4 again. Come up with a new hypothesis based on both experiment results and your original observation, and test it with a new experiment. Keep repeating steps 2 through 4 until the experiment proves one of your hypotheses.
  6. Once an experiment proves your hypothesis, your hypothesis can be reported to the scientific community as a valid theory.

Of course, if your hypothesis is proven to be true immediately in the first experiment, then steps 2 through 4 don’t need to be repeated and step 5 isn’t necessary. Sometimes scientists get lucky and prove their hypothesis on the first experimental try, but more often than not, they don’t. Multiple experiments are usually needed before a hypothesis can become a proven theory.

Knowing the scientific method will help you immensely on ACT Science questions that require deductive reasoning. You will sometimes be asked to identify a fact that is probably true, based on the data you see. At other times, a question may present a new observation or variable that was not mentioned in the passage and you’ll need to use the logic of the scientific method to infer the impact of the new data.

Beyond those specific question types, the ACT incorporates knowledge of the scientific method comprehensively throughout the Science section. Every ACT Science passage and question set revolves around experiments and/or data collected from experiments. A fluency in the scientific method will allow you to take in ACT Science information with confidence and good comprehension.

Reading ACT Science Charts

Think of this as the ‘treasure hunt.’ Unlike similar questions on the ACT Reading Test, finding the right answer on the ACT Science Test depends on your ability to read charts, rather than passages. The key to success lies in recognizing labels. Skim the questions first, marking any term that looks important. Once you’ve matched a term in the chart to a term used in a question, you know exactly where to look for the answer. The rest of the information (most of it useless) will no longer confuse you or stress you out.

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Using ACT Science Charts

The chart treasure hunt is over. For this question type, you’ll be given a scenario (ex: a variable in the experiment has changed) and have to use the chart to figure out the possible outcome. Though you’re making an educated guess, the chart will provide all the information you need to answer the question successfully, so don’t let your guess stray too far from what you see.

ACT Science Graphs

While scientists use graphs to visualize data and see patterns in their results, graphs can present unique challenges to the ACT test taker. Questions involving graphs will likely ask you to use both a graph and a corresponding chart. As long as you’re focusing on the keywords mentioned in the question, the excess data should not confuse you.


5 Most Frequently Tested ACT Science Topics -Magoosh

Even in such a ‘busy’ graph, a question will typically ask you about a single line of data.


What Comes Next?

These questions will ask you to decide what the experimenter should do next. The key to these questions is knowing what the experiment is trying to do. Again, they don’t require any deep knowledge of science, only strong reasoning skills and an ability to “tune out” inessential information.


5 Most Frequently Tested ACT Science Topics -magoosh

If we look at the first paragraph, we see that scientists want to know about “high altitudes and the effects of the air pressure changes.” If that’s what the scientists want to learn about, our next step needs to have something to do with high altitudes and air pressure.


Comparing and Inferring

This last question type appears only with the the Comparing Viewpoints passage on the ACT Science Test. Ever do a compare/contrast activity in English or history class? If so, you know what you need to do to answer these questions correctly. If not, it all boils down to finding similarities and differences in the two opinions.

The hardest topic for many students is the inference questions. To improve your inference skills, spend extra time analyzing your results after taking a timed practice test. Good practice tests provide detailed explanations for each answer. If you consistently make mistakes with inference questions, analyzing the right answer will help you build the skill you need to succeed.

ACT Science: Scientific Terms

Bonus! You can find definitions for the following terms and study them on our ACT Flashcard mobile or web app!

The ACT Science section will occasionally include questions in which the answer requires science knowledge that is not provided in the passage.

Here is a list of basic scientific topics that the ACT might test. But don’t panic! Anything tested will be on a very basic level (something you might have learned in an introductory class or even remember from middle school), and you will only see a few questions per test that require any outside knowledge at all.

To get some more tips on ACT science practice, follow this link for strategies, questions and explanations!


  • classifications: genus, species (e.g. knowing that lizards are mammals, reptiles or amphibians)
  • human anatomical systems (circulatory, digestive, respiratory)
  • eukaryotic and prokaryotic organisms
  • photosynthesis
  • pollination
  • metamorphosis
  • genetics (allele, genes, chromosomes, X and Y chromosomes)
  • proteins
  • DNA
  • RNA
  • ribosomes
  • mitochondria
  • chromosome
  • genotype
  • osmosis
  • phenotype
  • dominant and recessive traits
  • crossing over of dominant and recessive alleles
  • mitosis
  • meiosis
  • cellular division phases (interphase, etc.)



  • understanding (and balancing) chemical equations and reactions
  • atom
  • nucleus
  • ion
  • molecule
  • solute
  • solution
  • solvent
  • reactant
  • product
  • solubility
  • atomic mass
  • solid, liquid, gas
  • pH
  • acid
  • base
  • viscosity
  • condensation
  • evaporation
  • electrons
  • protons
  • neutrons
  • atomic number
  • atomic mass
  • molar mass
  • isotopes
  • solid, liquid, gas and melting, boiling, freezing points (very generally speaking; not specific to any particular substance, except maybe water)
  • important elements (e.g. water is H20)



  • velocity
  • acceleration
  • polarity
  • buoyancy
  • waves
  • amplitude
  • frequency
  • wavelength
  • charges (like charges attract; opposite charges repel)
  • circuits (capacitor, resistor)
  • amperes
  • volts
  • convection
  • conduction
  • radiation
  • kinetic energy
  • potential energy
  • gravitational potential energy
  • mechanical energy
  • density


Earth and Space

  • metamorphism (state change)
  • layers of earth
  • erosion
  • altitude
  • air resistance
  • orbit
  • terrestrial planet/gas giants


Other Science Terms

  • independent variable
  • dependent variable
  • control
  • hypothesis
  • endothermic
  • exothermic
  • ectothermic
  • matter
  • mass


That’s all for now, ACT scientists. Good luck, and don’t let those graphs and charts psych you out!

Unless otherwise specified, all images from Wikimedia Commons: LadyofHats, Emichan & Miraceti, Sharon Bewick, Mats Halldin, Brazosport College

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  • Thomas Broderick

    Thomas spent four years teaching high school English, social studies, and ACT preparation in Middle Tennessee. Now living in Northern California, he is excited to share his knowledge and experience with Magoosh's readers. In his spare time Thomas enjoys writing short fiction and hiking in the Sonoma foothills.

By the way, Magoosh can help you study for both the SAT and ACT exams. Click here to learn more!

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