ACT Mixed Science Practice Questions with Answers

Concept Explanation

ACT Mixed Science refers to a set of practice questions that combine biology, chemistry, physics, and Earth sciences to simulate the diverse data interpretation and scientific reasoning required for the exam. The ACT Science section does not test rote memorization of facts but rather your ability to analyze graphs, tables, and conflicting viewpoints. Effective preparation involves moving between different scientific disciplines while maintaining a focus on the scientific method and experimental design. By engaging with ACT Mixed Science practice questions with answers, students learn to identify variables, interpret trends, and draw conclusions under timed conditions.

To excel in this section, you must understand the three primary passage types: Data Representation, Research Summaries, and Conflicting Viewpoints. While a Data Representation passage might ask you to read a single graph about soil pH, a Research Summary might detail two experiments on plant growth, and a Conflicting Viewpoint passage will present two scientists arguing over the cause of dinosaur extinction. Integrating your ACT Prep strategy with these diverse topics ensures that no single subject—be it thermodynamics or genetics—catches you off guard on test day.

Solved Examples

The following examples demonstrate how to approach different scientific disciplines using the same analytical framework.

1. Physics Example: A student measures the force required to pull a 5 kg block across different surfaces. Surface A requires 10 N, Surface B requires 15 N, and Surface C requires 5 N. Which surface has the highest coefficient of friction?
   1. Identify the relationship: Friction force is directly proportional to the coefficient of friction when the mass is constant.
   2. Compare the values: 15 N (Surface B) is the highest force recorded.
   3. Conclusion: Surface B has the highest coefficient of friction because it required the most force to move the block.
2. Chemistry Example: A scientist observes that the solubility of a salt increases from 20g/100mL at $25^\circ \text{C}$ to 45g/100mL at $60^\circ \text{C}$. Based on this, what is the likely solubility at $40^\circ \text{C}$?
   1. Establish the trend: Solubility increases as temperature increases.
   2. Determine the range: $40^\circ \text{C}$ is between $25^\circ \text{C}$ and $60^\circ \text{C}$.
   3. Interpolate: The solubility at $40^\circ \text{C}$ must be between 20g and 45g. A value around 32-35g would be a logical scientific estimate.
3. Biology Example: In a study of Mendelian genetics, two heterozygous tall pea plants ($Tt$) are crossed. What percentage of the offspring is expected to be short ($tt$)?
   1. Set up a Punnett square: The possible genotypes are $TT, Tt, Tt,$ and $tt$.
   2. Count the recessive phenotypes: Only the $tt$ genotype results in a short plant.
   3. Calculate: 1 out of 4 possible outcomes is $tt$, which equals 25%.

Practice Questions

Test your skills with these ACT Mixed Science practice questions with answers covering various scientific domains.

1. A researcher finds that as the concentration of a catalyst increases, the time required for a chemical reaction to reach completion decreases. If a 1% concentration takes 60 seconds and a 2% concentration takes 30 seconds, how long would a 4% concentration likely take if the trend continues linearly?

2. In an Earth Science study, seismic waves are measured. P-waves travel at 6 km/s and S-waves travel at 3.5 km/s. If a station records a P-wave at 12:00:00 PM, would the S-wave arrive before or after 12:00:00 PM?

3. A biologist observes that a specific bacteria population doubles every 20 minutes. If the starting population is 100 cells, how many cells will be present after one hour?

4. An astronomer notes that Star A has a surface temperature of 3,000 K and appears red, while Star B has a surface temperature of 10,000 K and appears blue. Which star is emitting higher energy photons according to Wien's Law?

5. In a physics lab, a pendulum's period is measured. When the string length is 0.5m, the period is 1.4s. When the length is 2.0m, the period is 2.8s. Does increasing the length of the string increase or decrease the period?

6. A chemist mixes an acid with a pH of 2.0 and a base with a pH of 12.0. If the resulting solution is perfectly neutralized, what should the final pH be?

7. A study on plant transpiration shows that at 20% humidity, a plant loses 5g of water per hour. At 80% humidity, the plant loses 1g of water per hour. What is the relationship between humidity and transpiration rate?

8. According to the NASA climate evidence, atmospheric $\text{CO}_2$ levels have risen significantly. If a graph shows $\text{CO}_2$ at 300 ppm in 1950 and 410 ppm in 2020, what is the average rate of increase per decade?

9. A circuit contains a 10-ohm resistor and a 5-volt battery. Using Ohm's Law ($V = IR$), what is the current in amperes?

10. In a study of soil horizons, Horizon A is found at 0-10cm depth, and Horizon B is at 10-30cm. Which horizon is likely to have a higher concentration of organic leaf litter?

Answers & Explanations

1. 15 seconds. The relationship shows that doubling the concentration halves the time (1% to 2% halved 60 to 30). Doubling again from 2% to 4% would halve 30 to 15.
2. After 12:00:00 PM. S-waves travel slower (3.5 km/s) than P-waves (6 km/s), so they always arrive later than P-waves from the same source.
3. 800 cells. One hour contains three 20-minute intervals. 100 doubles to 200, 200 to 400, and 400 to 800.
4. Star B. Higher temperatures correspond to shorter wavelengths and higher energy photons (blue light has more energy than red light).
5. Increase. The data shows that as length increased from 0.5m to 2.0m, the period increased from 1.4s to 2.8s.
6. 7.0. On the pH scale, a value of 7.0 represents a neutral solution, which is the goal of mixing equivalent strengths of acid and base.
7. Inverse relationship. As humidity increases (20% to 80%), the transpiration rate decreases (5g to 1g).
8. ~15.7 ppm per decade. Total increase is 110 ppm over 70 years. $\frac{110}{7} \approx 15.7$ ppm per 10-year period.
9. 0.5 Amperes. Using $I = \frac{V}{R}$, $I = \frac{5}{10} = 0.5$.
10. Horizon A. Organic matter and leaf litter accumulate on the surface and top layers of soil.

1. If Experiment 1 uses a 5g sample and Experiment 2 uses a 10g sample of the same substance, which is considered the independent variable?

• AThe temperature of the room
• BThe mass of the sample
• CThe chemical composition
• DThe time of the reaction

Frequently Asked Questions

What subjects are covered in ACT Mixed Science?

The section covers biology, chemistry, physics, and Earth/space sciences. However, the focus is on your ability to interpret data and logic rather than your prior knowledge of these specific subjects.

Do I need to memorize formulas for ACT Science?

Generally, no, as most formulas are provided within the passage or the questions. Occasionally, very basic concepts like density or the definition of a pH scale are helpful to know beforehand.

How many questions are in the ACT Science section?

There are 40 questions that must be completed within 35 minutes. This requires a fast pace of just under one minute per question, including the time spent reading the passages.

What is the best way to improve my ACT Science score?

Consistent practice with varied passage types is essential. You should focus on identifying trends in graphs and using our AI Question Generator to target specific weaknesses in data interpretation.

Are the questions in the Mixed Science section harder than single-subject ones?

They are not necessarily harder, but they require more mental flexibility. Being able to switch from a biology mindset to a physics mindset quickly is a skill developed through using ACT Mixed Science practice questions with answers.