ACT Science Section: Facts your students need to know

Misconceptions about the ACT Science Section

As a professional tutor, I spend a lot of time helping students maximize their scores on the Science Section of the ACT.  As I tell my students, one of the things you need to do is make sure you have a strong background of science facts from your middle school years.

There are a lot of misconceptions about the ACT Science Section.  Yes, it does cover physics, chemistry, biology, astronomy, meteorology, geology, and a few other “ologies.”  Yes, the passages are at the high school and even the college level.  However, that doesn’t mean you can’t do well on this test if you haven’t taken high school-level classes in all these topics.  The ACT Science test is passage-based, meaning all (or at least most) of the information you need to answer the questions is given to you.  For instance, I was working on a passage with a student today that referred to tomato plants as Solanum lycopersicum and pepper plants as Capsicum annuum.  Does that mean you need to memorize the Latin names of thousands of species to do well on this test?  Of course not!  The first paragraph of the passage explained which plants were which.  When you saw the Latin words a few paragraphs down, you just had to have the presence of mind to look back for the detail you needed.

What you really need to do well on the ACT Science Section is the ability to think like a scientist.  You need to read and process technical information very quickly.  The questions will ask you to find specific details mentioned in the passages or find patterns and trends in tables of data.  All of this will need to happen at a very brisk pace.  In my opinion, the most challenging part of the ACT Science Section isn’t getting the correct answers, but doing so in a very limited amount of time.  There are two tips I give my students to accomplish this task.

Tips to Maximize Your Speed

First, you shouldn’t read the passages first.  In fact, you should barely read them at all.  Instead, you should go right to the questions and scan the passage for the answers.  (Please keep in mind that this strategy is only for the ACT Science Section.  In the reading section, you should absolutely read the passages first.)  In the science section, you’ll find that the topics are extremely complex and include several details you’ll never need to answer the questions.  Attempting to fully understand the passages is a surefire way to run out of time.  It breaks my teacher’s heart to say this, but you’ll have to stifle your scientific curiosity to do well on this test. If you encounter a word you don’t know in a question, there’s usually no need to figure out what it means.  Instead, scan the passage and the data to see where that word is mentioned.  Usually, you can determine the answer to the question at hand without ever learning the definition of the word.  If you do need to know the definition, only then should you take a look at the first paragraph, where applicable terms are most often defined.  (Please bring your scientific curiosity back for all non-timed types of scientific reading!)

The second tip I have for speeding up the ACT Science Section is to make sure your background knowledge is as strong as possible.  Even if you didn’t take AP Chemistry in high school, you probably had a chemistry unit in a middle school science class.  So you probably know that water has the chemical formula H2O.  Here’s an example of how that can be useful:

If the researchers had collected the gas that was produced by the boiling water and analyzed its components, which of the following elements would they be most likely to identify?

A) Carbon

B) Nitrogen

C) Oxygen

D) Neon

If you know that water is made of up hydrogen and oxygen, then you don’t have to read the passage at all to know the answer to this question will be C.  Once again, I would never recommend this for the reading section, but in the science section, trust your knowledge!  These passages will include topics you’ve never heard of, but there will also be things you do know about, such as water.  Moreover, everything in these passages will be scientifically accurate, so there’s no need to double-check that the authors got their facts right. It is safe to circle C and move on to the next question without referencing the passage for this one.  This will give you more time to spend scanning the passage when you’re working on the harder questions.

Not only should you trust your own scientific knowledge for questions where the answers are in the passage, but you’ll also find about 2-3 questions on the test where you have no other option.  My example above is actually modeled on an actual test question in this category.  If you had gone back to the passage to look for one of the elements listed, you would have never found it.  You might have spent more than a minute looking for something you already knew.  If you insist on always finding confirmation in the passage, then these quick and easy questions can become big time wasters.

The Science Facts You Need to Know

In order to help my students best prepare for the ACT Science Section, I’ve prepared the following list of science facts to know.  I analyzed about two dozen ACT science tests and idenified the topics that were found in a question but not specified in the passage.  These are the ACT Science Facts you need to know!

Experimental Design

  • Independent vs Dependent Variables
  • Control Groups
  • Holding other variables constant (aka “controlling for a variable”)
  • Common conversions in metric system (1000 mm = 100 cm = 1 m = 1000 km)
  • “Lab words” to know: tare, balance, graduated cylinder, filter, distill


  • Animal Cell Structure (cell membrane, nucleus, ribosomes, mitochondria)
  • Plant Cell Structure (cell wall, nucleus, chloroplast)
  • Photosynthesis (plants use light, water, and CO2 and produce glucose and O2)
  • Cellular Respiration (cells convert O2 and glucose into H2O, CO2, and energy in the form of ATP)
  • Greenhouse Effect
  • Erosion
  • Popular research methods: how bacteria are grown and counted in a lab, the transect method
  • Genetics (Punnett squares, Women have XX, Men have XY)
  • Systems in the human body (endocrine system, nervous system, digestive system, etc.)


  • Density/Buoyancy
  • pH Scale (0-6=acid; 7=neutral; 8-14=base)
  • Recognize the abbreviations for common elements and compounds (O, C, H, N, Fe, H2O, H2, CH4, NH4, OH, NaCl, etc.)
  • Atomic structure (protons, neutrons, electrons)
  • How to read a molecular diagram
  • How to read a phase change diagram
  • Exothermic vs. Endothermic
ExothermicReaction gives off heatEnvironment gets warmer
EndothermicReaction takes in heatEnvironment gets cooler


  • Free body diagrams, including friction and normal force.
  • Gravity
  • V=IR (Voltage is in volts, Current is in Amps, and Resistance is in Ohms Ω)
  • Terrestrial Planets vs. Gas Giants, Solar System (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus)
  • Popular research methods: free fall tower, Atwood machine, photocell, the double slit experiment

Here’s a link to a handy PDF of the list above:

Science Facts you should know for ACT


If you want to do your best on the ACT, you’ll need to prepare.  Make sure to take a science class in school every year and learn all you can.  If you missed any specific classes, take the time to look up the facts from my list you didn’t have a chance to learn.  In addition, you will need to do several practice science sections under timed conditions.  There is no substitute for practice.  If you search the internet, you’ll find several ACTs that were given in past years and then released as practice tests.  These are the best preparation you can get. If you find that you need more support to reach your goals, there are several ACT classes you can take.  You can also consider hiring a tutor like me.

I’d like to finish up with a story about my student, Ting.   Ting had already taken the ACT and earned scores of 34-36 on the first three sections.  Since the maximum score for any section is a 36, those scores are amazing!  However, her science score was only 25.  She hired me just to get that science score up with the others.  We met weekly for six weeks, and each time I have her two practice tests for homework.  Ting scored a perfect 36 on her last three practice tests!  When I asked her what made the biggest difference for her, she called it mindset.  She explained she had to put her natural curiosity on hold and get laser-focused on getting the answer and moving on to the next question.  She had always been distracted by all the other “really cool science stuff” in the passages.  Ting already had an excellent foundation of scientific knowledge.  Once she learned the correct technique, all that was left was several rounds of timed practice.  Hopefully, this advice will help you as well, and you can find the same success when you take the ACT Science Section!

About the Author: Heather Krey

Passionate about helping her students achieve their college dreams by being their coach and cheerleader as they prep for the SAT and ACT, Heather Krey is an experienced instructor with teaching certificates in math, physics, chemistry, and English. She knows the best tips and strategies for these tests – and she also understands that students need encouragement and practice to do their best. With dual bachelor’s degrees in industrial engineering and psychology from Lehigh University, she also holds masters of education degrees in mathematics from DeSales University and in teaching from Kutztown University. Heather lives in Allentown, PA, with her husband and three children.

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