Free Praxis Middle School Science Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Praxis Middle School Science practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which finding provides empirical support for a claim about the natural world?

   1. A.A prediction repeated in several textbooks
   2. B.Measurements collected during a controlled investigationCorrect answer: B
   3. C.An explanation endorsed by a well-known scientist
   4. D.An interpretation preferred by most students

   Explanation: ETS identifies scientific knowledge as "Based on empirical evidence". Measurements supply observations that can test the claim; repetition, authority, and preference alone do not.

   Reference: ETS Middle School Science Study Companion — p. 6, I.A.1.b

2. 2An isotope has atomic number 12 and mass number 25. How many neutrons does its nucleus contain?

   1. A.12
   2. B.13Correct answer: B
   3. C.25
   4. D.37

   Explanation: DOE defines mass number as the "total number of protons" plus the "total number of neutrons". Thus neutrons = 25 − 12 = 13.

   Reference: DOE Fundamentals Handbook: Chemistry, Volume 1 — Module 1, p. 4, Atomic Mass Number

3. 3Which structure is the basic living unit that makes up a multicellular organism?

   1. A.An organ
   2. B.A tissue
   3. C.A cellCorrect answer: C
   4. D.An organ system

   Explanation: MedlinePlus states, "Cells are the basic building blocks of all living things." Tissues, organs, and organ systems are larger levels of organization made from cells.

   Reference: MedlinePlus Genetics: What Is a Cell? — What is a cell?, opening paragraph

4. 4In which galaxy is our solar system located?

   1. A.Andromeda
   2. B.The Milky WayCorrect answer: B
   3. C.Triangulum
   4. D.The Large Magellanic Cloud

   Explanation: NASA states, "Our solar system is located in the Milky Way, a barred spiral galaxy". The other options name other galaxies, rather than the galaxy containing the Sun and its planets.

   Reference: NASA Solar System Facts — Introduction

5. 5Repeated, carefully checked observations conflict with an accepted scientific explanation. How should the explanation be treated?

   1. A.Preserved because acceptance establishes its final form
   2. B.Rejected solely because any disagreement disproves it
   3. C.Reexamined and revised if the new evidence warrants revisionCorrect answer: C
   4. D.Evaluated by counting supporters instead of testing predictions

   Explanation: ETS describes major concepts as "Subject to revision in light of new evidence". Reliable conflicting evidence warrants reevaluation; acceptance is neither immunity from testing nor a reason for automatic rejection.

   Reference: ETS Middle School Science Study Companion — p. 6, Nature of Science and Engineering, Nature of scientific knowledge, revision-in-light-of-evidence subitem

6. 6Which pair represents isotopes of the same element?

   1. A.Atoms with 6 protons and 6 neutrons; atoms with 6 protons and 8 neutronsCorrect answer: A
   2. B.Atoms with 6 protons and 6 neutrons; atoms with 8 protons and 6 neutrons
   3. C.Atoms with 6 protons and 8 neutrons; atoms with 7 protons and 7 neutrons
   4. D.Atoms with 6 protons and 6 neutrons; atoms with 7 protons and 6 neutrons

   Explanation: DOE states, "Atoms of the same element with different atomic mass numbers are called isotopes." Only the first pair keeps proton number constant while changing neutron number.

   Reference: DOE Fundamentals Handbook: Chemistry, Volume 1 — Module 1, p. 4, Atomic Mass Number

7. 7Which structure houses most of the hereditary DNA in a typical human body cell?

   1. A.The nucleusCorrect answer: A
   2. B.The Golgi apparatus
   3. C.A ribosome
   4. D.A lysosome

   Explanation: In its Nucleus entry, MedlinePlus states, "It also houses DNA (deoxyribonucleic acid), the cell’s hereditary material." The nucleus houses most human cellular DNA; the source separately notes the smaller amount of mitochondrial genetic material.

   Reference: MedlinePlus Genetics: What Is a Cell? — Nucleus entry

8. 8Which description best matches the origin of the solar system in the solar-nebula model?

   1. A.The cloud expanded because gravity pushed its particles away from one another.
   2. B.The planets reached full size before the disk material began to collide and clump.
   3. C.A gas-and-dust cloud collapsed into a disk, and material accreted.Correct answer: C
   4. D.Planets grew mainly by fragmentation of large bodies into ever-smaller pieces.

   Explanation: NASA states, "When this dust cloud collapsed, it formed a solar nebula – a spinning, swirling disk of material." The same Formation section describes particles clumping and collisions producing larger objects. Collapse and accretion, rather than gravitational repulsion or progressive fragmentation, match the model.

   Reference: NASA Solar System Facts — Formation

9. 9An astronomer compares telescope observations, while a chemist varies conditions in a laboratory. What makes both approaches compatible with science?

   1. A.Scientific investigations can use methods suited to their questionsCorrect answer: A
   2. B.Every scientific investigation must manipulate its study system
   3. C.Observational studies become scientific only after laboratory replication
   4. D.Different scientific disciplines require identical experimental procedures

   Explanation: ETS includes "Use of a variety of methods" in the nature of scientific knowledge. Both observation and experimentation can investigate natural phenomena; laboratory manipulation is not universal.

   Reference: ETS Middle School Science Study Companion — p. 6, I.A.1.a

10. 10A neutral atom contains 17 protons. How many electrons does it contain?

    1. A.0
    2. B.8
    3. C.17Correct answer: C
    4. D.34

    Explanation: DOE states that "equal and opposite charges cancel each other". A neutral atom therefore has 17 negative electrons balancing its 17 positive protons.

    Reference: DOE Fundamentals Handbook: Chemistry, Volume 1 — Module 1, Characteristics of Atoms, electron discussion