Updated August 21, 2026

5 ACT Science Strategy Tips for Understanding Experiments

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Understanding science experiments is a big part of ACT Science.

That can be challenging, because experiments on the ACT often cover science topics you probably haven’t studied in school.

But with the right strategies, you can solve any ACT Science question. Here are the 5 most useful strategy tips we teach students for ACT Science questions on experiments.

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Jump to section:
What’s an “Understanding Experiments” question on ACT Science?
Strategy Tip #1: Skim the passage, but lead with the questions
Strategy Tip #2: Start with questions that you can answer just with visuals
Strategy Tip #3: Know your independent and dependent variables
Strategy Tip #4: For “why” questions, ask what the scientists are controlling
Strategy Tip #5: Label the exact differences between experiments
Next steps

What’s an “Understanding Experiments” question on ACT Science?

Questions about Understanding Experiments on ACT Science often involve understanding the experimental design, reading and interpreting the experimental results, and understanding why a certain step was taken in the experimental design.

Typical Understanding Experiments questions might look like this:

Why did the scientists most likely place the test tubes in a darkened room?

Which of the following statements about the relationship between the alloy density and melting point is consistent with the results of Experiment 2?

Which of the following was an independent variable in Experiment 1?

Understanding Experiments is one of the basic ACT Science question types that goes with Research Summaries passages. That’s one of the 3 passage types on the ACT Science section.

Each Research Summaries passage will describe the design of an experiment – usually 2 or 3 variations on a similar experiment. You’ll also be given data on the experimental results in the form of tables, graphs, or other figures.

You can find strategies and tips for approaching Research Summaries passages right here, plus more in our guide to everything you need to know about ACT Science.

Here’s an example ACT Science question on understanding experiments:

In seawater, compound X is broken down into simpler compounds by thermal energy at temperatures above 50 degrees Fahrenheit. What action was taken in the studies to prevent this process from taking place?

A. Each mixture of compound X and seawater was cooled.
B. Each mixture of compound X and lake water was cooled.
C. Each mixture of compound X and seawater was exposed to light.
D. Each mixture of compound X and lake water was exposed to light.

We’ll break this question down in detail later on. Now, let’s get into the strategies to approach these questions.

Strategy Tip #1: Skim the passage, but lead with the questions

We often advise students to skip straight to the questions on ACT Science. That’s because you can answer many questions correctly without reading the passage very thoroughly – sometimes without reading it at all.

On questions about experimental design, you will need some information from the passage. But you don’t need to understand the experiment in detail. All you need to do is understand what part of the experiment served which goal.

Instead of close-reading the passage, skim the passage and circle or underline key words or phrases as you read. Then go to the questions.

Strategy Tip #2: Start with questions that you can answer just with visuals

After you skim the passage, start with the questions that just ask for data from figures, like this example.

Which of the following statements about the relationship between the number of seedlings per square meter and the average root-to-shoot ratio is consistent with the results of Experiment 3? On average, as the number of seedlings per square meter increased, the average root-to-shoot ratio:

A. decreased only.
B. increased only.
C. remained the same.
D. varied with no general trend.

What not to do for a question like this is to start combing through the passage! You do not need to understand the experiment at all to answer this question.

Instead, go straight to the figure that shows the study’s results.

Group	Seedlings/square meter	Seedling mortality (%)	Root-to-shoot ratio
1	10	12	0.7
2	12	4	0.6
3	18	2	0.4
4	24	8	0.3

Table 3

Using your pencil or the annotation tool on the on-screen test, circle what you’re looking for. You want to know what happens to the root-to-shoot ratio as the seedling density increases.

Looking at Table 3, you can see that the seedling density goes up as you go down the table. What happens to the root-to-shoot ratio? It goes down, so you can select answer A. (You’re not being asked about the exact relationship, just the general trend.)

This strategy isn’t intuitive or even comfortable for most students, which is one reason ACT tutoring can be a big help. Give us a call to see how ACT tutoring could help you, or find the right match in our expert-reviewed ranking of the best ACT tutoring services out there.

Strategy Tip #3: Know your independent and dependent variables

You can ace ACT Science with almost no background knowledge.

We said almost. While most questions are just about reading and interpreting the information on the test, you might see a few questions that require you to know some basic terms – especially terms about science experiments.

Two of the most important terms to know are independent and dependent variables.

The independent variable is controlled and changed by the scientist. (It’s usually on the x-axis of a graph.)
The dependent variable is not controlled or changed by the scientist. (It’s usually on the y-axis of a graph.)

Some students remember this with a simple mnemonic: “I, the scientist, change the Independent variable.”

Whether or not you get asked directly what the independent or dependent variable is, it’s always helpful to label them as you skim the passage. That will help you understand the whole experimental design.

Which of the following was a dependent variable in Experiment 1?

A. pH of the water
B. SGR
C. stocking density of the shrimp
D. diet of the shrimp

Neocaridina davidi, a species of freshwater shrimp, are kept in many home aquariums. Two experiments were conducted to determine how diet and stocking density (number of shrimp per liter of water, shrimp/L) affect the specific growth rate (SGR; percent increase in length per day, percent/day) in N. davidi.

Experiment 1
Each of 12 identical 10 L tanks received 8 L of freshwater with a specific hardness of 8 dGH, a temperature of 22°C, and a pH of 7.5. Hardness, temperature, and pH were kept constant over the course of the experiment. N. davidi of similar lengths were selected, and their lengths were measured, in mm. They were then equally distributed among the tanks at a stocking density of 2 shrimp/L. The tanks were then divided equally into 4 groups.

For 3 months, each group was fed a different diet (Diets Q–T). Each group was fed twice a day. At the end of 3 months, the length of each shrimp was measured, in mm, and the SGR of each shrimp was calculated. The average SGR was then determined for each group (see Table 1).

You’re looking for the dependent variable, so you want the variable that the scientists did not control.

From the passage, the pH was kept constant, and the stocking density was also constant across all the groups, so these were not variables in the experiment.

The shrimp were fed different diets, controlled by the scientists, so this was the independent variable.

At the end of the experiment, the scientists measured the SGR for each group of shrimp. They did not control SGR; it varied (presumably) depending on the shrimp’s diets. So SGR was the dependent variable: answer B. (Again: you don’t have to know what SGR is or even what it stands for to get this question right!)

Strategy Tip #4: For “why” questions, ask what the scientists are controlling

ACT Science loves to ask you why scientists took a certain step in their study, or what they did to achieve a certain outcome.

Obviously, you can’t read their minds. But if you know their goal, and you know what they did, then you can understand why they did something specific in the experimental design.

For a lot of these questions, you can reason your way to the answer without even reading the passage, like in this question:

In seawater, compound X is broken down into simpler compounds by thermal energy at temperatures above 50 degrees Fahrenheit. What action was taken in the studies to prevent this process from taking place?

E. Each mixture of compound X and seawater was cooled.
F. Each mixture of compound X and lake water was cooled.
G. Each mixture of compound X and seawater was exposed to light.
H. Each mixture of compound X and lake water was exposed to light.

The key strategy here is to sketch the cause-and-effect relationship.

Seawater + higher temperature → compound X gets broken down

If thermal energy – meaning heat – causes this compound to break down, and we want to prevent this from occurring, it makes sense that you’d want to cool the water down.

We’re talking about seawater, not lake water, so you can cross off answers B and D straight away. Light exposure has nothing to do with the cause-effect relationship, so you can also eliminate answer C. That leaves answer A: to prevent the process from happening, the seawater mixture was cooled.

Strategy Tip #5: Label the exact differences between experiments

ACT Science will usually present you with two or three very similar variations on an experiment. Then, you’ll be asked to compare the experimental designs or outcomes.

Whether you’re taking the ACT on paper or on the computer, label each experiment as you skim the passage. That will help you answer questions more quickly, since you won’t have to dive back into the details to remember what each experiment is doing.

As you skim the passage, circle or underline the independent variable, or jot it down next to the experiment description. Here’s an example:

Experiment 1
In all trials, the temperature was 72 °C, and the pH was 5. From trial to trial, the mass of A and AG was varied.

Experiment 2
In all trials, the mass of A and AG was 2.5 g, and the temperature was 72 °C. From trial to trial, the pH was varied.

Experiment 3
In all trials, the mass of A and AG was 2.5 g, and the pH was 5. From trial to trial, the temperature was varied.

Now, when you see a question about the effect of pH on the results, you’ll jump straight to Experiment 2. ACT Science has 40 questions to answer in just 40 minutes, so saving even a minute can make a big difference!

If you’re aiming for a highly competitive or perfect ACT score, you’ll need to master time-saving strategies like this one. That’s where a specialist ACT tutor can make a big difference, helping you to learn and practice the key strategies you’ll need.

These are 5 essential strategies to improve your ACT Science score – and we have more in this post. Ready to practice? Try these strategies on 9 of the hardest ACT Science questions out there.

Next Steps

How do you get all these ACT Science strategies to become second nature? Practice, practice, practice!

An ACT expert can also help you figure out the best strategies for your own strengths and weaknesses on ACT Science. We’ve been working with students preparing for the ACT for over two decades, and many of our tutors achieved perfect scores on the ACT themselves. Our students often see their scores go up by several points over just a few months of tutoring.

Learn more about our programs here, and get in touch with our team for a free consultation on the right option for you.

5 ACT Science Strategy Tips for Understanding Experiments

5 ACT Science Strategy Tips for Understanding Experiments

What’s an “Understanding Experiments” question on ACT Science?

Strategy Tip #1: Skim the passage, but lead with the questions

Strategy Tip #2: Start with questions that you can answer just with visuals

Strategy Tip #3: Know your independent and dependent variables

Strategy Tip #4: For “why” questions, ask what the scientists are controlling

Strategy Tip #5: Label the exact differences between experiments

Next Steps

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