Medium ACT Science Practice Questions

Success on the ACT Science section depends more on your ability to interpret trends and experimental designs than on memorizing complex biology or chemistry formulas. While the test covers physics, chemistry, biology, and Earth sciences, the core challenge lies in extracting information from tables, graphs, and conflicting viewpoints. By engaging with Medium ACT Science Practice Questions, students can bridge the gap between basic literacy and the high-level reasoning required for a top-tier score.

Concept Explanation

Medium ACT Science Practice Questions focus on multi-step data interpretation, identifying relationships between variables, and understanding the logic behind experimental procedures. Unlike easy questions that might only ask you to find a single value in a table, medium-level questions require you to synthesize data from two different sources or predict a trend based on existing patterns. This level of practice often involves ACT data analysis where you must determine if a relationship is direct (both variables increase together) or inverse (one increases while the other decreases).

To excel at this level, you should be familiar with the following components:

• Interpolation and Extrapolation: Estimating values between known data points or predicting values beyond the provided range.
• Experimental Variables: Distinguishing between independent variables (what is changed), dependent variables (what is measured), and constants (what stays the same).
• Conflicting Viewpoints: Comparing two or more scientific hypotheses to identify where they agree or disagree on a specific mechanism.

For more foundational work, you might visit our ACT Prep hub to see how these skills integrate with the overall exam structure. Understanding the ACT scientific method is particularly useful for medium-level questions that ask about why a specific control group was used or how a change in equipment might impact results.

Solved Examples

Use these worked examples to understand the logical steps required for medium-difficulty science problems.

1. Example 1: Identifying Trends

   A study measures the solubility of Salt X in water at different temperatures. At $20^\circ \text{C}$, the solubility is $30 \text{g}/100 \text{g}$ of water. At $40^\circ \text{C}$, it is $50 \text{g}/100 \text{g}$. At $60^\circ \text{C}$, it is $70 \text{g}/100 \text{g}$. What is the likely solubility at $50^\circ \text{C}$?

   1. Identify the relationship: As temperature increases by $20^\circ \text{C}$, solubility increases by $20 \text{g}$.
   2. Determine the rate: The increase is $1 \text{g}$ per $1^\circ \text{C}$.
   3. Calculate for $50^\circ \text{C}$: This is halfway between $40^\circ \text{C}$ and $60^\circ \text{C}$.
   4. Result: The solubility should be halfway between $50 \text{g}$ and $70 \text{g}$, which is $60 \text{g}/100 \text{g}$.
2. Example 2: Cross-Referencing Data

   Table 1 shows that Substance A boils at $100^\circ \text{C}$. Figure 1 shows a graph of pressure vs. boiling point where increasing pressure increases the boiling point. If the pressure is doubled, what happens to the boiling point of Substance A?

   1. Locate the initial state: Boiling point is $100^\circ \text{C}$ at standard pressure.
   2. Analyze the trend in Figure 1: There is a direct relationship between pressure and boiling point.
   3. Apply the change: Doubling the pressure follows the upward trend of the graph.
   4. Conclusion: The boiling point will be greater than $100^\circ \text{C}$.
3. Example 3: Experimental Design

   A scientist conducts an experiment to see how different light colors affect plant growth. She uses three identical pea plants, giving one red light, one blue light, and one green light. She measures their height after 2 weeks. What is the independent variable?

   1. Define independent variable: The factor intentionally changed by the researcher.
   2. Evaluate the setup: The researcher changed the color of the light for each plant.
   3. Conclusion: The color of the light is the independent variable.

Practice Questions

Test your skills with these Medium ACT Science Practice Questions. Ensure you refer back to the hypothetical data trends described in each prompt.

1. In an experiment measuring the rate of a chemical reaction, it was found that at $25^\circ \text{C}$, the reaction took 60 seconds. At $35^\circ \text{C}$, it took 30 seconds. At $45^\circ \text{C}$, it took 15 seconds. Based on this trend, how long would the reaction likely take at $55^\circ \text{C}$?

2. A student hypothesizes that the period of a pendulum depends only on its length. In Trial 1, a $0.5 \text{m}$ pendulum with a $1 \text{kg}$ mass has a period of 1.4 seconds. In Trial 2, a $1.0 \text{m}$ pendulum with a $1 \text{kg}$ mass has a period of 2.0 seconds. To further test the hypothesis that mass does NOT affect the period, what should the student use for Trial 3?

3. A researcher observes that as the concentration of a pollutant in a lake increases, the population of a certain fish species decreases. If the concentration is $5 \text{ppm}$, there are 500 fish. At $10 \text{ppm}$, there are 250 fish. At $15 \text{ppm}$, there are 125 fish. Is this a direct or inverse relationship, and how many fish would be expected at $20 \text{ppm}$?

4. Scientist 1 claims that global warming is caused primarily by methane emissions. Scientist 2 claims it is caused primarily by carbon dioxide. Both scientists agree that greenhouse gases trap heat. If a study shows that methane is 25 times more effective at trapping heat than carbon dioxide, which scientist's viewpoint is supported?

5. A graph shows that the density of a liquid decreases linearly as temperature increases. If the density is $1.0 \text{g/mL}$ at $4^\circ \text{C}$ and $0.96 \text{g/mL}$ at $24^\circ \text{C}$, what is the approximate density at $14^\circ \text{C}$?

6. In a study of soil pH, Sample A has a pH of 6.0 and Sample B has a pH of 7.0. If a plant grows $10 \text{cm}$ in Sample A and $15 \text{cm}$ in Sample B, what would be a reasonable prediction for its growth in Sample C with a pH of 8.0, assuming a linear relationship?

7. A physicist measures the force of gravity between two objects. When the distance is $d$, the force is $F$. When the distance is $2d$, the force is $\frac{1}{4}F$. If the distance is increased to $3d$, what will the force be according to the inverse-square law?

8. An experiment tests the effect of fertilizer on corn height. Group 1 receives no fertilizer, Group 2 receives $5 \text{g}$, and Group 3 receives $10 \text{g}$. All groups receive the same amount of water and sunlight. What is the purpose of Group 1?

Answers & Explanations

1. 7.5 seconds. The data shows that for every $10^\circ \text{C}$ increase, the reaction time is halved. Half of 15 seconds is 7.5 seconds.
2. A $0.5 \text{m}$ or $1.0 \text{m}$ pendulum with a different mass (e.g., $2 \text{kg}$). To test if mass affects the period, the student must change the mass while keeping the length constant to isolate the variable of interest.
3. Inverse relationship; 62.5 fish. It is inverse because as one variable increases, the other decreases. The population is halved for every $5 \text{ppm}$ increase. Half of 125 is 62.5.
4. Scientist 1. Scientist 1 focuses on methane. Evidence showing methane is a highly potent greenhouse gas directly strengthens the claim that methane is a primary driver of warming.
5. $0.98 \text{g/mL}$. Since the decrease is linear, the value at the midpoint temperature ($14^\circ \text{C}$) will be the average of the two densities: $\frac{1.0 + 0.96}{2} = 0.98$.
6. $20 \text{cm}$. The growth increased by $5 \text{cm}$ for every 1.0 unit increase in pH. Adding another 1.0 unit to the pH (from 7.0 to 8.0) should result in another $5 \text{cm}$ of growth.
7. $\frac{1}{9}F$. The inverse-square law states that force is proportional to $\frac{1}{d^2}$. Since $3^2 = 9$, the force becomes $\frac{1}{9}$ of the original.
8. It serves as the control group. Group 1 provides a baseline to compare how much the fertilizer actually affects growth compared to no fertilizer at all.

1. If a graph shows a line sloping downward from left to right, what does this indicate about the two variables?

• AThey have a direct relationship
• BThey have an inverse relationship
• CThey have no relationship
• DOne variable is constant

Frequently Asked Questions

How many science questions are on the ACT?

The ACT Science section consists of 40 questions that must be completed in 35 minutes, requiring a pace of about 52 seconds per question. These questions are spread across six or seven passages covering various scientific disciplines.

Do I need to know advanced physics for ACT Science?

No, you do not need advanced physics knowledge because the test provides almost all the information you need in the passages. Most questions test your ability to read ACT graph analysis and interpret experimental data rather than recall specific scientific facts.

What is the difference between interpolation and extrapolation?

Interpolation is the process of estimating a value that falls within the range of your existing data points on a graph or table. Extrapolation involves extending that trend to estimate a value that lies beyond the highest or lowest measured points.

How can I improve my speed on the science section?

Improving speed requires practicing with ACT mixed science practice questions and learning to go straight to the questions before reading the entire passage. You should only read the detailed text if a question specifically asks about the experimental setup or conflicting theories.

What are the three types of passages in ACT Science?

The three types are Data Representation (graphs and tables), Research Summaries (descriptions of experiments), and Conflicting Viewpoints (arguments between scientists). Each type requires a slightly different approach to data retrieval and logical reasoning.