Prior knowledge questions | Types of questions | ACT Science

Questions that require you to know a particular fact from a science topic are called prior knowledge questions. These questions are very rare, but are definitely some of the most tricky questions you can come across. The difficulty is that you either know the fact or you don’t. Here is an example of a prior knowledge question:

ACT science prior knowledge question Source: ACT Assessment Practice Test 16MC1, 2016

As you probably noticed, this is a question that you either know or you don’t. If you are familiar with the chemical equation for photosynthesis, you’d likely recognize the answer to be D. Unfortunately, if you are not familiar with the equation, not even the passage will help you come to the correct solution.

So, if the passages won’t help you solve these questions when they come up, how can you be better prepared to answer them?

The trick to answering these questions is not to memorize them; you might benefit much more from using your time to study other areas of the test. Additionally, prior knowledge questions from the past will likely never be tested again in the same way. After all, test makers want these questions to catch you off guard. Instead, one of the best ways to prepare for these questions is by treating them as inference questions.

Treat prior knowledge questions as inference questions

If you have not read through the chapter on Inference questions, please do that before continuing this chapter. You should have a good understanding of the problem-solving process detailed in that chapter to get a good idea of what we are talking about in this chapter.

Following the problem-solving process, you will treat a prior knowledge problem exactly the same as an inference problem. You look for the answer in the passage, then use the answers to help you narrow down the solution, and finally make your best educated guess. The difference for these questions is that you will find little to nothing in the passages relating to the question or the answers.

Spend as much time looking for the answer in the passage as you would any other kind of question. This way, you don’t need to know whether it is a prior knowledge question or not. You simply follow the process as normal and make your best educated guess. Don’t be afraid to make an educated guess! If you don’t know the details you are expected to remember, an educated guess is the best option you have.

Common topics for prior knowledge questions

If you are comfortable enough with the science portion and feel that the only thing left for you to improve on is by getting these prior knowledge questions right, then read this subsection. Below, you will see a list of the most common topics of prior knowledge questions:

Chemistry

Molecular structures (atoms, protons/neutrons/electrons)
Phases of matter (solid, liquid, gas, boiling point, freezing point)
Density (solids are more dense than liquids, liquids are more dense than gasses)
Unit changes (see [Unit conversions] chapter in Math section of this book)
Charges (Protons are positive, electrons are negative. Opposite charges attract)
pH (scale 0–14, 0 is most acidic and 14 is most basic. Water is neutral at 7)

Biology

Taxonomy (domain, kingdom, phylum, class, order, family, genus, species)
Genetics (Punnett squares, DNA, genotype/phenotype, gamete)
Photosynthesis (Plants take in CO₂, water, and sunlight. They produce oxygen and sugar or glucose)

Earth Science/Astronomy

Layers of the earth
Order of the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)

Focus on these topics only after you have practiced the other areas of this guide. This should be one of the last things that you study!

Key points

Question type. These questions focus on the knowledge you are expected to already know.

Strategy. Focus less on memorizing the questions and more on what you should do if you come across questions that you can’t find the answer to. Treat them as inference questions.

Problem-solving process. Follow the problem-solving process so that you can make your best effort to answer these questions even if you don’t know the answer. This way, you don’t need to identify when a problem is a prior knowledge question.

Common topics. If you are comfortable with your performance on all other aspects of the science test, then you may benefit from studying these common topics for prior knowledge questions: molecular structures, phases of matter, density, unit changes, charges, pH, taxonomy, genetics, photosynthesis, planet order, and layers of the earth.