What distinguishes easy from hard questions is that most of the easier problems are data grab problems, where you simply find the one data point or the single line in the paragraph and you have your answer. In contrast, the most challenging ACT Science questions ask you to use multiple data points to come to an answer. They will take you longer to answer and are harder to get right.

The following are the common difficult ACT question types.

1. Sneaky data grab questions

Some sneaky data grab questions will require you to look in strange places for the answers, such as the introduction! ACT makers assume that students skip the introduction. However, sometimes the answers to a question may be in the introduction.

EXAMPLE 1:

Passage 1

Substances in the atmosphere, such as \(CU^2^+) , \(Zn^2^+) , \(Cl^-) and \(SO_4^2^-) ions, are carried down to Earth’s surface by precipitation. This process is known as wet deposition, \(CU2^a) and \(Zn^2^+) ions ar eput into the atmosphere y high temperature combustion processes. The presence of Cl and \(SO_4 ^2^-) ions in the atmosphere can be attributed to road-salt dust and electrical power generation, respectively.

Suppose there had been no precipitation during 1 entire month of the 12-month period. based on the information provided, during that month there would have been:

A. significant wet deposition of all substances

B. significant wet deposition of \(CU^2^+) and \(Zn^2^+), but no wet deposition of \(Cl^-) and \(SO_4 ^2^-)

C. no wet deposition of any of the 4 substances

D. no wet deposition of \(CU^2^+) and \(Zn^2^+) , but significant wet deposition of \(Cl^-) and \(SO_4 ^2^-)

Solution: 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 is 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. C is the correct answer.

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

2. Synthesize two 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:

Example 2:

Based on Figures 1 and 2, for a given mass of \(O_2) at 22 C, how does the pressure exerted by the \(O_2) in a 6 L vessel compared to the pressure exerted by the \(O_2) in a 3 L vessel? In the 6 L vessel, the \(O_2) presuure will be:

A. 1/2 as great as in the 3 L vessel

B. the same as in the 3 L vessel

C. 2 times as great as in the 3 L vessel

D. 4 times as great as in the 3 L vessel

Solution: Let’s look at 2g of \(O_2) added for both the figures. In the 3L vessel the pressure is 400 torr, while in the 6L vessel, it is 200 torr. So for any given amount of \(O_2) added, the pressure in the 6L vessel is half the amount of pressure in the 3L vessel. So, the answer is A.

Example 3:

Which of the following conclusions is best supported by Figures 1 and 2? The wavelength that results in the highest rate of photosynthesis also results in the?

A. lowest relative absorption by chlorophyll a

B. lowest relative absorption by chlorophyll b

C. highest relative absorption by chlorophyll a

D. highest relative absorption by chlorophyll b

Solution: 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. Since, the question first mentions the wavelength with the highest rate of photosynthesis, we will start by using Figure 2. You need to find the graph’s maximum. The highest peak in rate of photosynthesis is at about 108% at a wavelength of 440 nm.

The next step is finding the relative absorption of chlorophyll a and b of a wavelength of 440 nm - in between the second tick mark and 450 mark on figure 1. We see the dotted line is at its 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.

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:

Example 4:

Based on the figure, a sound of a given frequency will have the highest intensity for which of the following sets of conditions?

Solution: 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). You see S (10^-^8%) is represented by the two vertical lines at the 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 - measured on the x-axis. Both lines for S (10^-^8%) have a measured intensity between -20 and 0 db. 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, B and D. Now, to decide between A and C, 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 A.

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.. Take the problem step-by-step, use process of elimination and check every part of the graph for information (every axis and key).