ACT Science Practice

ACT Science Practice

In order to be accepted into college, you will more than likely need to take an entrance exam, depending on the school that you wish to attend. One entrance exam that you will need to take is the ACT exam. The ACT exam measures high-school students on what they have learned during high school and determines if they are ready to enter college-level classes. The ACT also gives you an idea as to which college-level classes you are prepared to take.

What to Expect on the ACT Exam

The ACT exam consists of four sections:

  1. English
  2. Math
  3. Reading
  4. Science

There is also a Writing Section on the ACT exam that is optional.

To prepare for the ACT exam, it is best to take multiple ACT practice tests to see which areas you will need more work on as well as what you can expect on the actual exam. Our ACT Science Practice is similar to those science questions you will be asked on the actual ACT exam.

What’s on the ACT Exam


The Science section of the ACT exam includes 40 questions and is timed for 35 minutes. The Science section measures the interpretation, analysis, evaluation, reasoning, and problem-solving skills that are required in the natural sciences. The Science section includes questions about:

  • Interpretation of Data
  • Scientific Investigation
  • Evaluation of Models, Inferences, and Experimental Results

Pollutants typically enter seawater at point sources, such as sewage discharge pipes or factory waste outlets. Then, they may be spread over a wide area by wave action and currents. The rate of this dispersal depends upon a number of factors, including depth, temperature, and the speed of the currents. Chemical pollutants often attach themselves to small particles of sediment, so that studying the dispersal of sediment can help in understanding how pollution spreads.

In a study of this type, a team of scientists lowered screened collection vessels to various depths to collect particles of different sizes. This gave them an idea of the size distribution of particles at each depth. Figure A shows the results for six different sites (ND, NS, MD, MS, SD, and SS). The particle size is plotted in phi units, which is a logarithmic scale used to measure grain sizes of sand and gravel. The 0 point of the scale is a grain size of 1 millimeter, and an increase of 1 in phi number corresponds to a decrease in grain size by a factor of ½, so that 1 phi unit is a grain size of 0.5 mm, 2 phi units is 0.25 mm, and so on; in the other direction, -1 phi unit corresponds to a grain size of 2 mm and -2 phi units to 4 mm. Grains of different size are carried at different rates by the currents in the water. The study also measured current speed and direction, pressure and temperature at different depths, and at different times of year. The results were used in a computer modeling program to predict the total transport of sediments both along the shore (north-south) and perpendicular to it (east-west . Figure B shows the program’s calculation of the distance particles would have been transported during the study period. The abbreviation mab in the figure stands for meters above bottom.

ACT Science Question 25

ACT Science Question 25

Which of the following sites was found to have the smallest average particle size?





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ACT Flashcards
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ACT Secrets









C: Of the sites listed, the phi value for site MD, 2.73 phi, is the largest value. The text explains how phi varies inversely with particle size, so these are the smallest particles.

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Jay Willis

Jay Willis joined Mometrix as Vice President of Sales in 2009, and has developed several key strategic relationships that have enhanced the distribution of Mometrix products. With nearly 20 years of sales experience in the publishing industry, his dedication to providing the highest quality experience for customers, coupled with his sales and marketing expertise, has resulted in significant growth of the Institutional Sales division. Learn more

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