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The Hardest ACT Science Questions and Strategies to Solve Them

Posted by Dora Seigel | Jun 4, 2015 8:30:00 AM

ACT Science



In every section on the ACT, there are some questions that are more difficult than the others. Science is no different. However, unlike the math section, where the questions progress from easy to hard in a linear fashion, each of the 7 passages tends to have 1-2 hard questions that can appear at any point in the passage (though they tend to be the last questions of the passage).   

These problems may seem challenging at first glance, but they're really just slightly more challenging than the others if you use the right ACT Science strategies and tips that we'll be covering in this guide

Here's what distinguishes easy from hard questions. Most of the easier problems on the ACT Science section are data grab problems, where you simply find the one data point or the single line in the paragraph, and you have your answer. Occasionally, you have to interpret that data, but not in a complicated way. In contrast, the most challenging ACT Science questions ask you to use multiple data points to come to an answer. They'll take you longer to answer and are harder to get right.

Here are the question types I'll cover:

  • Sneaky data grab questions
  • Using multiple visuals to answer the question
  • Using multiple data points within a single visual to answer the question
  • Questions that require outside knowledge

Hopefully by the end of this article, you'll feel able to conquer any hard question!


Difficult Type #1: Sneaky Data Grab Questions

Some sneaky data grab questions will require you to look in strange places for the answer to your question, such as the introduction!

ACT makers assume that with such a short time frame (35 minutes to answer 40 questions) students will skip the introduction. If you have time management issues on ACT Science, my recommended strategy is to answer the questions without reading the passage, using the visuals alone, skipping the questions you can’t answer with visuals and saving them for the end of the passage. Read more about the strategy by learning about the 3 types of ACT Science passages

However, when you do go back and skim, include the introduction in your skimming. The introduction typically holds nuggets of gold. Check out this sneaky data grab ACT science practice question:




There was nothing in the visuals to help you answer the question. You had to read this short introduction to find the answer:




All four substances are carried down by precipitation, and the process is known as wet deposition. The question is still phrased in a slightly confusing way. In the introduction, it tells you what happens if there is precipitation; it fails to mention what happens when there is no precipitation. 

It's safe to assume since it wasn’t mentioned that what normally happens during precipitation will NOT happen without precipitation. So, there will be no wet deposition of the 4 substances since all 4 are normally carried down by precipitation.

NOTE: Do not get tricked by the flip in relationship. The ACT Science section often asks these questions to trick you.

Don’t rule out any part of the passage! Sometimes the answer will be where you least expect it.


Difficult Type #2: Synthesize 2 or More Different Graphs

While most questions on the ACT Science section only require you to use one data point within one visual, some of the more difficult questions require you to find more information. Like this question below:




Start by analyzing the question. What is it asking you to find? 

When you look at a question, and it asks you about 2 different values, you should realize that this means you will need to grab and compare at least two different pieces of data. In this case, the question asks you about the pressure exerted by O2 at 6 L and at 3 L at 22 degrees Celsius, two different values, so you should be looking for at least those two pieces of data.

The question specifically asks you to compare the pressure in 6 L vessel to the pressure in the 3 L vessel at "a given mass of O2." That phrase, "a given mass of O2," is code for at ANY mass of O2 added. In order to find this data, you will need to use Figure 1 and 2 (as the question told you).

Your next step should be to figure out the difference between Figure 1 and 2 (see what I did there?). 





Figure 1 represents the results from the 3 L vessel, and Figure 2 represents the results from the 6 L vessel. Knowing this, we now need to compare the pressure across all masses of O2 added in the 3 L and 6 L vessels, since as I said above that is what the question is really asking. 

To do an appropriate comparison, I recommend grabbing 2-3 data points, preferably widespread. Zero is always a safe place to start. In this case, in both the 3 L and 6 L vessel the pressure at 0 g of O2 added is 0 torr, which makes logical sense since no O2 added means nothing to exert the pressure. Note: it is not important to understand the units.

Next data point: let's look at 2 g of O2 added. In the 3 L vessel, the pressure is 400 torr, while in the 6 L vessel the pressure is 200 torr.

I recommended spreading out the data points, so for our last point, we will look at the maximum mass of O2 added, 10 g. In the 3 L vessel, the pressure is 1800 torr, and in the 6 L vessel, the pressure is 900 torr. Below I have synthesized all of the data into a table, this way we can clearly see the comparison of the pressure in the 6 L vessel to the pressure in the 3 L vessel:




So for any given amount of O2 added (outside of 0), the pressure in the 6 L vessel is half the amount of pressure in the 3 L vessel. So, the answer is A.

Do you get the gist here? As a recap, our strategy for solving this practice question was: 

  • we understood what the question was asking for (comparing pressure in 6L vs. 3L containers)
  • we found the two graphs representing the 6L and 3L containers
  • we found the O2 line for each graph
  • we picked the same mass of gas added for both graphs and compared the O2 pressures to find that the ratio between the 6L and 3L container was 1:2

Let’s attack one more of these, taking it step-by-step: 




Let's first figure out what the question is asking of us. The phrasing of this question is slightly more confusing than the last one. It mentions Figure 1 and 2, so we know that we will need to look at both.

However, this question doesn't ask for a specific number to look at on the graph, like 10 meters or 550 wavelengths. When this happens, it's harder to pick out the data. When no numbers are mentioned, look for words indicating value such as highest, lowest, biggest, smallest. These words imply numbers and comparisons and give you a hint on how to read the graph.

Reading the question closely, we see the question is asking us to find the wavelength with the highest rate of photosynthesis and then see what its relative absorption of chlorophyll a and b are. Let's take this step-by-step.

Start by figuring out the difference between Figure 1 and 2. Figure 1 shows the relative absorptions of chlorophyll a and b by wavelength. Figure 2 shows the rate of photosynthesis for a variety of wavelengths. Since, the question first mentions the wavelength with the highest rate of photosynthesis, we will start by using Figure 2 below: 

You need to find the graph’s maximum. The maximum is where the rate of photosynthesis is highest. The highest peak in rate of photosynthesis is at about 108% at a wavelength of 440 nm. 




Now, we have completed the first step. The next step is finding the relative absorption of chlorophyll a and b of a wavelength of 440 nm. Looking at Figure 1, it is a little tricky because the intervals of wavelength measure are different. Figure 2 begins at 400 measuring in 20 nm intervals until 720, whereas Figure 1 measures in 25 nm intervals from 400 to 750. 

Finding 440 nm on Figure 1, in between the second tick mark and 450 mark, we see the dotted line is at it’s maximum and the solid line is low but not at the minimum. Reading the key, we see the dotted line represents the relative absorption of chlorophyll a.




The solid line represents the relative absorption of chlorophyll B. So, the relative absorption of chlorophyll A is at a maximum, and the relative absorption of chlorophyll B is low but not at a minimum. Thus, the answer is C.

When you are looking at multiple visuals to answer a question, take the problem step-by-step:

  • Start by finding what the question is asking you.
  • Next, figure out the difference between the figures.
  • Find one data point, then move to the next. 
  • Take your time and use process of elimination to help you.   


Difficult Type #3: Analyze Multiple Data Points Within a Single Visual

This is one of the trickiest question types on the ACT Science section. And here is one of the hardest tough questions I’ve seen. Not only is the graph crazy, the question requires you to analyze four data points within the graph. Here is the question:




Let's break it down. The question is asking you which of the answer choices has the highest intensity at a given frequency. As we discussed above, whenever a question states "at a given X," it means across all values of X. In other words, this question is asking you to pick the answer choice with the highest intensity across all frequencies.

There is a lot of information in the graph below, but the answer choices only require us to consider four conditions: in air or in water, and at S of 100% or at 10^-8%. 

Looking at the graph below, you may have no idea where to begin:





Start by finding the locations of S 100% and S 10^-8% (it is completely fine that you don’t understand what these mean). I don’t even think the passage helped you understand what these mean. I don’t know what they mean, but I can still answer the question correctly. 

You see S 10^-8% is represented by the two vertical lines at the far left of the graph. S 100% is represented by the two vertical lines at the far right of the graph.




Now, you need to locate intensity, since the question asked specifically which has the highest intensity. Intensity is measured on the x-axis. Both lines for S 10^-8 % have a measured intensity between -20 and 0 db (again, understanding the units is not important). Both lines for S 100% have a measured intensity between 180 and 220 db. 




The S 100% are at a higher intensity, so we can eliminate both S 10^-8% answer choices, G and J. 

Now, to decide between F and H, we need to figure out whether the intensity was greater in water or air. To do this, we need to distinguish which S 100% line represents water and which one represents air. 




According to the key, the small dotted line represents water, and the thicker line represents air. The small dotted line is just to the right of the thicker line, so it is at a higher intensity than the thicker line. S 100% in water has an intensity of approximately 205 db and S 100% in air has an intensity of approximately 195 db, so the answer is F. 

Look how far we've come since the beginning of this section? This graph looked indecipherable, but step by step we were able to break it down.

This question is very do-able, you just need to be diligent in your graph reading (if you need more help with this skill check out our article on Factual Questions). Take the problem step-by-step, use process of elimination and check every part of the graph for information (every axis and key). 


Difficult Type #4: Questions That Require Outside Knowledge

There are around 4 questions per test that you will not be able to answer correctly without outside knowledge. Check out our other article for an overview of the topics the ACT expects you to know. Without memorizing these topics, it will be nearly impossible to score between 33 and 36.



Hard questions are not that hard. They require the same skills as the easy questions, but you need to do more steps. These questions take longer because they're more complex.

ACT Science Tips to remember for these hardest questions:

  • Don’t rule out any part of the passage!
    • Sometimes the answer will be where you least expect it such as in the introduction.
  • Do not get tricked by the flip in relationship. The ACT Science section often asks these types of questions to trick you.
  • When you are looking at multiple visuals to answer a question, take the problem step-by-step.
    • Figure out what the question is asking you.
    • Figure out which figures you need to use.  
    • Find one data point, then move to the next.
    • Take your time and use process of elimination to help you.  
  • When pulling multiple data points from one visual, also take the problem step-by-step.
    • Start by analyzing the question.
    • Figure out which figures you need to use and the difference between them (one last time!).
    • Use process of elimination.
    • Look at every piece of the graph.
    • Make sure to read keys and scan every axis.
  • Study the topics that the ACT Science section expects you to know.


What’s Next?

I hope you feel ready to tackle any hard question the ACT Science section throws at you! As your next steps in studying for the ACT Science section, learn the 3 types of ACT Science passagesthe only actual science you need to know for ACT Science, and the best way to study and practice for ACT Science


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Dora Seigel
About the Author

As an SAT/ACT tutor, Dora has guided many students to test prep success. She loves watching students succeed and is committed to helping you get there. Dora received a full-tuition merit based scholarship to University of Southern California. She graduated magna cum laude and scored in the 99th percentile on the ACT. She is also passionate about acting, writing, and photography.

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