Repeated measurements close to each other (but maybe not to the truth)

A consistent shift in one direction — hurts accuracy; fix at the source

Unpredictable scatter — reduced by averaging many trials

Meter, kilogram, second, kelvin, ampere, mole, candela

How long is the Praxis 5435 test?

Total testing time is 2 hours and 30 minutes (150 minutes) for the roughly 135 selected-response questions. It is delivered on computer at Praxis test centers and through at-home testing where available.

What is a passing score on the Praxis 5435?

Praxis 5435 is reported on a 100–200 scaled-score range, and the passing score is set by each state or licensing agency, not by ETS. Many states require around 141, but cutoffs vary — for example, some jurisdictions set it higher. Always confirm the exact passing score required where you plan to teach.

What topics does the Praxis 5435 cover?

Four content categories: Nature and Impact of Science and Engineering (scientific method, measurement, engineering design), Physical Science (chemistry and physics), Life Science (cells, genetics, evolution, ecology), and Earth and Space Science (geology, the atmosphere, and astronomy). Physical Science is the largest category.

Is the Praxis 5435 hard?

The 5435 is broad rather than deep — it samples introductory physics, chemistry, biology, and earth and space science, so the challenge is range, not advanced difficulty. Candidates who studied one science area but not the others should focus their review on the unfamiliar categories, especially Physical Science.

How should I study for the Praxis 5435?

Work through all four content categories module by module, starting with Physical Science since it carries the most weight. After each module, take the checkpoint quiz to find gaps, then drill that category with our free practice questions and flashcards before sitting a full, timed practice test.

Does the Praxis 5435 include formulas or a calculator?

An on-screen calculator and a list of physical constants and conversions are provided for the relevant questions, so you do not need to memorize numeric constants. You should still know the core relationships — such as F = ma, density = mass ÷ volume, and the photosynthesis and respiration equations — well enough to apply them quickly.

Is this Praxis 5435 study guide free?

Yes — the full guide, the checkpoints, the glossary, the practice questions, and the flashcards are 100% free, with no account required.

What is the difference between accuracy and precision?

Accuracy is how close a measurement is to the true value, while precision is how close repeated measurements are to one another. A set of readings can be precise (tightly clustered) yet inaccurate if a systematic error shifts them all away from the true value. This is a measurement skill in the Nature of Science category. A miscalibrated balance that always reads high gives precise but inaccurate results. Random error scatters readings and is reduced by averaging many trials; systematic error shifts every reading the same way and must be corrected at the source.

What makes a hypothesis scientific?

A scientific hypothesis must be testable and falsifiable — there must be a possible observation or experiment that could prove it wrong. It is usually a specific, often 'if/then' prediction about how an independent variable affects a measurable outcome, not a vague or untestable statement. Falsifiability is the key requirement. 'Plants grow taller with more light' is testable; 'plants prefer sunlight' is not. A valid test changes only one independent variable, holds other variables constant, and includes a control group for comparison.

How is a scientific theory different from a scientific law?

A scientific law describes a consistent natural pattern, often mathematically, but does not explain why it happens — like Newton's law of gravitation. A scientific theory is a broad, well-tested explanation supported by a large body of evidence, such as the theory of evolution or plate tectonics. A theory is not a guess; it is among the strongest forms of scientific knowledge because so much evidence supports it. Laws and theories serve different roles: laws tell you what happens, theories explain why.

What determines the identity of a chemical element?

The number of protons in an atom's nucleus — its atomic number — determines which element it is. Changing the number of neutrons makes an isotope of the same element, and changing electrons makes an ion, but only the proton count fixes the element's identity. This is a core Physical Science (chemistry) concept. Carbon is any atom with 6 protons, regardless of neutrons or charge. Mass number is protons plus neutrons; isotopes share a proton count but differ in mass number.

How do periodic-table trends like atomic radius and electronegativity change?

Across a period (left to right), atomic radius decreases while ionization energy and electronegativity increase, because added nuclear charge pulls electrons in tighter. Down a group, atomic radius increases as new electron shells are added, so electronegativity and ionization energy decrease. Elements in the same group share chemical properties because they have the same number of valence electrons. Fluorine, at the top right, is the most electronegative element; the most reactive metals sit at the bottom left.

What does the law of conservation of mass mean for a chemical reaction?

Mass is neither created nor destroyed in a chemical reaction, so the total mass of the reactants equals the total mass of the products. Atoms are only rearranged, which is why a chemical equation must be balanced — the same number of each atom appears on both sides. This is a foundational Physical Science (chemistry) principle and the reason equations are balanced with coefficients. Energy is also conserved overall; reactions that release energy are exothermic, those that absorb it are endothermic.

What does Newton's second law tell you about force and motion?

Newton's second law states that the net force on an object equals its mass times its acceleration (F = ma). For a given force, a more massive object accelerates less; for a given mass, a larger net force produces a larger acceleration. Zero net force means no acceleration. This is a core Physical Science (physics) concept. The first law (inertia) is the special case where net force is zero. Newton's third law adds that forces come in equal, opposite pairs acting on different objects.

What is the law of conservation of energy?

Energy cannot be created or destroyed; it only changes form. A swinging pendulum trades gravitational potential energy for kinetic energy and back, and friction converts some to heat — but the total energy of a closed system stays constant throughout. This Physical Science principle underlies analysis of machines, circuits, and heat transfer. Simple machines can multiply force, but they never multiply energy or work, which are conserved.

How does the electromagnetic spectrum relate energy and wavelength?

The electromagnetic spectrum runs from radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. As you move toward gamma rays, frequency and energy increase while wavelength decreases. Visible light is only a small band in the middle of this range. All electromagnetic waves travel at the speed of light in a vacuum, related by v = f λ (speed equals frequency times wavelength). Higher-energy radiation (UV, X-rays, gamma) is more harmful to living tissue than lower-energy radio or infrared.

How are photosynthesis and cellular respiration related?

They are essentially reverse processes. Photosynthesis in chloroplasts uses light to turn carbon dioxide and water into glucose and oxygen, storing energy. Cellular respiration in mitochondria breaks glucose back down with oxygen to release that energy as ATP, returning carbon dioxide and water. The products of one process are the reactants of the other, so they form a balanced loop of carbon and energy in ecosystems. Respiration occurs in nearly all cells; photosynthesis occurs only in producers such as plants and algae.

What does cell theory state?

Cell theory has three core ideas: all living things are made of one or more cells, the cell is the basic unit of structure and function in life, and all cells arise from pre-existing cells. It applies to both prokaryotes, which lack a nucleus, and eukaryotes, which have one. Prokaryotic cells (bacteria) have no membrane-bound nucleus or organelles; eukaryotic cells (plants, animals, fungi) do. Key organelles include the nucleus (controls the cell, holds DNA), mitochondria (energy), and, in plants, chloroplasts (photosynthesis).

How does natural selection drive evolution?

Individuals vary in inherited traits. Those whose traits better suit their environment tend to survive and reproduce more, passing those traits to the next generation. Over many generations this shifts a population's traits — descent with modification — which is evolution by natural selection. Mutation is the ultimate source of new genetic variation; natural selection then acts on that variation. Evidence for evolution includes fossils, homologous structures, embryology, and DNA similarities across species.

How do dominant and recessive alleles determine an organism's traits?

Each gene has two alleles, one from each parent. A dominant allele is expressed whenever it is present, while a recessive allele is only expressed when an organism inherits two copies of it. The genotype (allele combination) determines the phenotype (the observable trait). A Punnett square predicts the ratio of offspring genotypes and phenotypes from the parents' alleles. Homozygous means two identical alleles (BB or bb); heterozygous means two different alleles (Bb), where the dominant trait shows.

How does energy flow through a food web?

Energy enters an ecosystem when producers capture sunlight through photosynthesis. It passes to consumers that eat producers and then to higher consumers, while decomposers recycle nutrients. Only about 10% of the energy transfers to the next level; the rest is lost mostly as heat. Because energy drops sharply at each trophic level, food chains rarely exceed four or five links. Matter cycles (carbon, nitrogen, water) but energy flows one way through an ecosystem and must be continually resupplied by the Sun.

What drives the movement of Earth's tectonic plates?

Convection currents in the mantle, powered by Earth's internal heat, slowly move the rigid plates of the lithosphere. Where plates diverge, new crust forms; where they converge, one plate subducts; where they slide past one another, earthquakes occur. Plate motion explains continental drift. This is a core Earth Science concept. Most earthquakes and volcanoes cluster along plate boundaries, especially the Pacific 'Ring of Fire.' Wegener proposed that today's continents were once joined as Pangaea and have since drifted apart.

How does the rock cycle convert one rock type into another?

The rock cycle continually transforms igneous, sedimentary, and metamorphic rock. Magma cools to form igneous rock; weathering and erosion break rock into sediments that compact into sedimentary rock; heat and pressure change existing rock into metamorphic rock; and melting returns rock to magma. Any rock type can become any other given the right process — there is no fixed one-way order. Sedimentary rock most often contains fossils because it forms gently from layered sediments rather than from heat or melting.

What causes Earth's seasons?

Seasons are caused by the tilt of Earth's axis, about 23.5 degrees, not by Earth's distance from the Sun. As Earth orbits, the hemisphere tilted toward the Sun receives more direct sunlight and longer days, producing summer, while the hemisphere tilted away has winter. A common misconception is that summer happens when Earth is closest to the Sun — in fact the Northern Hemisphere's summer occurs near Earth's farthest point. Earth's daily rotation on its axis causes day and night; its yearly revolution around the Sun defines the year.

The factor a researcher deliberately changes in an experiment to test its effect; it is plotted on the x-axis.

The outcome measured in an experiment; it responds to (depends on) the independent variable and is plotted on the y-axis.

The group in an experiment that does not receive the treatment, providing a baseline for comparison.

A testable, falsifiable proposed explanation, often stated as an 'if/then' prediction about how variables relate.

How close a measurement is to the true value. Distinct from precision, which is how close repeated measurements are to each other.

How close repeated measurements are to one another. Measurements can be precise but inaccurate if a systematic error shifts them all.

A broad, well-substantiated explanation supported by a large body of evidence, such as evolution or plate tectonics — far stronger than a guess.

The number of protons in an atom, which defines the element's identity.

An atom of an element with the same number of protons but a different number of neutrons, giving it a different mass number.

An atom that has gained or lost electrons, giving it a net negative or positive charge.

A measure of an atom's tendency to attract bonding electrons; it increases up and to the right on the periodic table, peaking at fluorine.

A chemical bond formed when two nonmetal atoms share electrons.

A bond formed by the transfer of electrons from a metal to a nonmetal, creating oppositely charged ions that attract.

The principle that mass is neither created nor destroyed in a chemical reaction, so reactant mass equals product mass.

The net force on an object equals its mass times its acceleration, written F = ma.

The energy of motion, equal to one-half mass times velocity squared (KE = ½mv²); it grows with the square of speed.

FREE Praxis 5435 Study Guide 2026 + Readiness Score

This free Praxis General Science (5435) study guide teaches to the ETS Praxis General Science: Content Knowledge test — every content category the exam measures, organized the way ETS builds the test.^[1] The 5435 is the licensure exam for prospective secondary general-science teachers, and it is broad rather than deep: it samples introductory physics, chemistry, biology, and earth and space science.

Because the test spans four categories, this guide covers all of them — the and of Physical Science, the cells, of Life Science, and the geology and of Earth and Space Science — plus the nature-of-science skills that thread through all of them. It’s interactive, not a wall of text: every category has a built-in checkpoint quiz, hover-able glossary terms, worked examples, and concept questions.

Read this guide category by category, test yourself at each checkpoint, then round out your free Praxis 5435 prep with our practice questions and flashcards.

Praxis 5435 is one of the 7 Praxis exams — explore our Praxis study guides to compare and prep across the whole family.

Praxis 5435 Exam Snapshot

Praxis General Science (5435) at a glance (2026)
Detail	Praxis General Science (5435)
Questions	About 135 selected-response questions
Format	Computer-delivered; single-answer and multiple-answer questions
Total time	2 hours 30 minutes (150 minutes)
Score scale	100–200 scaled score
Passing score	Set by each state/agency (commonly ~141; varies — confirm yours)
Content categories	Nature & Impact of Science (~15%), Physical Science (~37%), Life Science (~26%), Earth & Space Science (~22%)
Tools provided	On-screen calculator and a list of constants/conversions
Who takes it	Prospective secondary general-science teachers
Publisher	ETS (Educational Testing Service)

Praxis General Science (5435) by content category (2026)

Physical Science

~37%~50 questions

Life Science

~26%~35 questions

Earth & Space Science

~22%~30 questions

Nature & Impact of Science & Engineering

~15%~20 questions

About 135 selected-response questions in 2.5 hours. Physical Science is the single biggest category — roughly a third of the test.

The four content categories are not weighted equally. Physical Scienceis the single biggest category — roughly a third of the test — so it deserves the most study time, followed by Life Science and Earth & Space Science.^[1] Spread your work across all four, but lead with the categories that carry the most questions:

Praxis 5435 content categories (2026 approximate shares)

Physical Science37% · ~50 questions

Life Science26% · ~35 questions

Earth & Space Science22% · ~30 questions

Nature & Impact of Science & Engineering15% · ~20 questions

ETS reports the number of questions in each category, which we have expressed as approximate percentages of the roughly 135 total.^[1]This guide teaches all four categories as four study modules, starting with the broad nature-of-science skills and then moving through Physical, Life, and Earth & Space Science.

1 · Nature & Impact of Science & Engineering

About 15% of the test (~20 questions). This category is about how science works — designing experiments, measuring and interpreting data, and the relationship among science, engineering, technology, and society.^[1]

Scientific Method & Experiments

A controlled experiment changes one and measures its effect on a , while holding every other factor constant and including a for comparison. A good is testable and falsifiable — there must be a way to prove it wrong.

The scientific method — an iterative loop

Conclusions feed new questions, so the process cycles rather than ending — that is what makes science self-correcting.

1. Ask a questionObserve something and pose a testable question about it.
2. Form a hypothesisPropose a falsifiable explanation, often an 'if/then' prediction.
3. Design an experimentChange one independent variable; hold all others constant; include a control group.
4. Collect & analyze dataMeasure the dependent variable; look for patterns, accounting for error.
5. Draw a conclusionDecide whether the data support or refute the hypothesis.

New questions ↺ — a conclusion usually leads back to step 1 with a refined question.

Measurement, Accuracy & Error

is closeness to the true value; is closeness of repeated readings to each other. A miscalibrated balance that always reads high is precise but inaccurate — that is a systematic error. Random error scatters readings and is reduced by averaging trials.

Accuracy vs. precision vs. error type
Term	What it means
Accurate	Close to the true value
Precise	Repeated measurements close to each other (but maybe not to the truth)
Systematic error	A consistent shift in one direction — hurts accuracy; fix at the source
Random error	Unpredictable scatter — reduced by averaging many trials
SI base units	Meter, kilogram, second, kelvin, ampere, mole, candela

Engineering, Technology & Society

Science seeks to understand the natural world; engineering applies that understanding to design solutions within real-world constraints such as cost, time, and safety. The engineering design process is iterative: define the problem, brainstorm, prototype, test, and redesign. Scientific and technological advances reshape society and raise ethical and environmental questions.

Checkpoint · Category 1 · Nature & Impact of Science

Question 1 of 10

In a well-designed experiment, what is the role of the independent variable?

2 · Physical Science

About 37% of the test (~50 questions) — the single biggest category. Physical Science is chemistry and physics: atoms and the periodic table, bonding and reactions, and forces, energy, waves, electricity, and magnetism.^[1]

Atoms & the Periodic Table

An atom has protons and neutrons in its nucleus and electrons around it. The (protons) defines the element; the mass number is protons plus neutrons. differ in neutrons, and an has gained or lost electrons. Elements in the same group share properties because they have the same number of valence electrons.

Periodic-table trends — direction of change

Trend	Right → Left across a period	Top → Bottom down a group
Atomic radius	increases	increases
Ionization energy	decreases	decreases
Electronegativity	decreases	decreases
Metallic character	increases	increases

Read across a period (a row) and down a group (a column). Atomic radius is the master trend — the others largely follow how tightly the nucleus holds the outer electrons.

Bonding, Reactions & Matter

An transfers electrons from a metal to a nonmetal; a shares electrons between nonmetals. Every reaction obeys , which is why chemical equations must be balanced. Acids donate H⁺ ions (pH below 7); bases accept them (pH above 7).

Forces, Motion & Energy

says net force equals mass times acceleration, $F = ma$ . is $KE = \tfrac{1}{2}mv^2$ and gravitational potential energy is $PE = mgh$ . By the , energy only changes form — it is never lost.

Waves, Electricity & Magnetism

Wave speed is $v = f\lambda$ (frequency times wavelength). The runs from radio (low energy) to gamma rays (high energy).^[4] In circuits, Ohm’s law is $V = IR$ ; in a series circuit current is the same everywhere, while in a parallel circuit voltage is the same across branches.

Core Physical Science relationships
Quantity	Relationship
Newton's second law	$F = ma$
Density	$\rho = \dfrac{m}{V}$
Kinetic energy	$KE = \tfrac{1}{2}mv^2$
Wave speed	$v = f\lambda$
Ohm's law	$V = IR$

Checkpoint · Category 2 · Physical Science

Question 1 of 10

What three subatomic particles make up a neutral atom, and where is most of its mass located?

3 · Life Science

About 26% of the test (~35 questions). Life Science covers cells and their energy processes, genetics and heredity, evolution and classification, and ecology.^[1]

Cells & Energy (Photosynthesis & Respiration)

says all living things are made of cells that come from pre-existing cells. in the chloroplast stores light energy in glucose, and in the mitochondria releases it as — the two are nearly reverse processes.

Photosynthesis and cellular respiration — reverse processes

Photosynthesis (chloroplast)6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂. Stores light energy in glucose.

Cellular respiration (mitochondria)C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ATP. Releases that stored energy.

The products of one are the reactants of the other — oxygen and glucose cycle between plants and all respiring cells, balancing carbon and energy in living systems.

Genetics & Heredity

DNA stores genetic information in base pairs (A-T, G-C). A is expressed when present; a recessive allele only shows with two copies. A Punnett square predicts offspring ratios. makes two identical cells for growth; makes four varied gametes for reproduction.

Evolution & Classification

drives evolution: individuals with traits better suited to their environment survive and reproduce more, shifting a population over generations.^[6] Mutation supplies the variation selection acts on. Organisms are classified in the order Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Ecology & Ecosystems

Energy flows one way through a food web: producers capture sunlight, consumers eat them, and decomposers recycle nutrients — with only about 10% of energy passing to each higher level. Matter, by contrast, cycles (the carbon, nitrogen, and water cycles).

Checkpoint · Category 3 · Life Science

Question 1 of 10

What is the overall purpose of photosynthesis in green plants?

4 · Earth & Space Science

About 22% of the test (~30 questions).Earth and Space Science covers Earth’s structure and plate tectonics, rocks and geologic time, the atmosphere and weather, and basic astronomy.^[1]

Earth’s Structure & Plate Tectonics

Earth’s layers, from outside in, are crust, mantle, liquid outer core, and solid inner core. explains how mantle convection moves the plates, producing earthquakes, volcanoes, and mountains along their boundaries.^[5]

Three types of plate boundary

DivergentPlates pull apartNew crust forms; mid-ocean ridges and rift valleys.

ConvergentPlates collideSubduction; volcanoes, mountains, deep trenches.

TransformPlates slide pastEarthquakes (e.g., San Andreas Fault).

Mantle convection drives all three. Most earthquakes and volcanoes cluster along these boundaries.

Rocks, Minerals & Geologic Time

The three rock types — , , and — continuously transform through the rock cycle. Fossils form mostly in sedimentary rock, and the says deeper layers are older.

The rock cycle

Igneous rockCooling & solidifying of magma or lava
Sedimentary rockWeathering, then compaction & cementation of sediments
Metamorphic rockHeat & pressure transform existing rock

Any rock can become any other: melting forms igneous, weathering and burial form sedimentary, and heat and pressure form metamorphic — continuously, over geologic time.

Atmosphere, Weather & Water

The atmosphere layers (troposphere, stratosphere with its ozone, mesosphere, thermosphere) surround Earth. The water cycle moves water through evaporation, condensation, and precipitation, and the traps heat that keeps Earth warm — with excess gas intensifying it. Weather is short-term; climate is the long-term average.

Astronomy & the Solar System

The eight planets orbit the Sun, a star powered by nuclear fusion. Earth’s daily rotation causes day and night, while its yearly revolution and the 23.5° axial tilt cause the seasons — not its distance from the Sun.^[7] Moon phases and eclipses come from the Sun-Earth-Moon geometry.

Checkpoint · Category 4 · Earth & Space Science

Question 1 of 10

Which layer of Earth lies directly beneath the crust and behaves as a slowly flowing solid that drives the movement of tectonic plates?

How to Use This Study Guide

A study guide is a map, not the whole territory — use it alongside the official ETS materials and our free tools. Because the 5435 is broad, the goal is even coverage across all four categories, so spaced, mixed practice beats one long cram. Lead with Physical Science (the biggest category), and give extra time to whichever science you studied least in school.

A study loop that actually works

1
Read a category here
Work through one content category at a time — start with Physical Science, the heaviest.
2
Take the checkpoint
The quick check at the end of each category exposes what didn't stick.
3
Drill the gaps
Send your weak category straight into the free practice questions and flashcards.
4
Take full, timed practice
Sit a full practice test to build stamina across all four categories, then review every miss.

Praxis 5435 Concept Questions

Common science concepts the Praxis 5435 actually measures — at least one per content category. Tap any card for a short, exam-ready answer backed by an authoritative source (ETS, NASA, USGS, and the NIH), then test yourself on them as flashcards.

Praxis 5435 Glossary

Quick definitions for the terms you’ll see most across the Praxis General Science (5435):

Accuracy: How close a measurement is to the true value. Distinct from precision, which is how close repeated measurements are to each other.
Atomic number: The number of protons in an atom, which defines the element's identity.
ATP: Adenosine triphosphate — the cell's main energy-carrying molecule, produced by cellular respiration.
Cell theory: The principle that all living things are made of cells, the cell is the basic unit of life, and all cells come from pre-existing cells.
Cellular respiration: The process by which cells break down glucose with oxygen to release energy as ATP, mainly in the mitochondria.
Conservation of energy: Energy cannot be created or destroyed, only transformed; the total energy of a closed system stays constant.
Conservation of mass: The principle that mass is neither created nor destroyed in a chemical reaction, so reactant mass equals product mass.
Control group: The group in an experiment that does not receive the treatment, providing a baseline for comparison.
Covalent bond: A chemical bond formed when two nonmetal atoms share electrons.
Dependent variable: The outcome measured in an experiment; it responds to (depends on) the independent variable and is plotted on the y-axis.
Dominant allele: A version of a gene that is expressed whenever it is present, masking a recessive allele.
Electromagnetic spectrum: The full range of electromagnetic waves — radio, microwave, infrared, visible, ultraviolet, X-ray, gamma — ordered by frequency and energy.
Electronegativity: A measure of an atom's tendency to attract bonding electrons; it increases up and to the right on the periodic table, peaking at fluorine.
Greenhouse effect: The warming of Earth's surface when atmospheric gases such as carbon dioxide and water vapor trap heat radiating from the surface.
Hypothesis: A testable, falsifiable proposed explanation, often stated as an 'if/then' prediction about how variables relate.
Igneous rock: Rock formed from the cooling and solidifying of molten magma or lava.
Independent variable: The factor a researcher deliberately changes in an experiment to test its effect; it is plotted on the x-axis.
Ion: An atom that has gained or lost electrons, giving it a net negative or positive charge.
Ionic bond: A bond formed by the transfer of electrons from a metal to a nonmetal, creating oppositely charged ions that attract.
Isotope: An atom of an element with the same number of protons but a different number of neutrons, giving it a different mass number.
Kinetic energy: The energy of motion, equal to one-half mass times velocity squared (KE = ½mv²); it grows with the square of speed.
Law of superposition: In undisturbed rock layers, the oldest layers lie at the bottom and the youngest at the top.
Meiosis: Cell division producing four genetically varied haploid gametes with half the chromosome number.
Metamorphic rock: Rock formed when existing rock is transformed by heat and pressure, such as marble from limestone.
Mitosis: Cell division producing two genetically identical diploid cells, used for growth and repair.
Natural selection: The process by which individuals with traits better suited to their environment survive and reproduce more, shifting a population's traits over generations.
Newton's second law: The net force on an object equals its mass times its acceleration, written F = ma.
Photosynthesis: The process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen, in the chloroplast.
Plate tectonics: The theory that Earth's rigid outer shell is broken into plates that slowly move over the softer mantle, driven by convection.
Precision: How close repeated measurements are to one another. Measurements can be precise but inaccurate if a systematic error shifts them all.
Scientific theory: A broad, well-substantiated explanation supported by a large body of evidence, such as evolution or plate tectonics — far stronger than a guess.
Sedimentary rock: Rock formed when sediments are compacted and cemented over time; it often contains fossils.

Free Praxis 5435 Study Materials & Resources

Everything you need to prepare for the Praxis General Science (5435) is free here — no paywall, no sign-up. This guide is the foundation; pair it with the rest of our free Praxis 5435 study materials for active recall, timed practice, and last-minute review:

Praxis 5435 Practice Test — exam-style questions across all four content categories, with explanations.
Praxis 5435 Flashcards — active-recall decks for the high-yield science facts, formulas, and vocabulary.

Praxis 5435 Study Guide FAQ

The Praxis General Science: Content Knowledge (5435) test has about 135 selected-response questions and a total testing time of 2.5 hours. The questions are drawn from four content categories: Nature and Impact of Science and Engineering, Physical Science, Life Science, and Earth and Space Science.

References

1.ETS. “Praxis General Science: Content Knowledge (5435) — Test Overview.” ETS. ↑
2.ETS. “About The Praxis Tests.” ETS. ↑
3.ETS. “Praxis Tests — Understanding Your Praxis Scores.” ETS. ↑
4.NASA Science. “Introduction to the Electromagnetic Spectrum.” NASA. ↑
5.U.S. Geological Survey. “Understanding Plate Motions.” USGS. ↑
6.National Human Genome Research Institute. “Evolution — Genetics Glossary.” NHGRI. ↑
7.NASA Space Place. “What Causes the Seasons?.” NASA. ↑

Sources for the concept answers

Every answer in the Praxis 5435 concept questions above is drawn from an official or authoritative primary source:

National Institute of General Medical Sciences. “Cells: The Basic Units of Life.” National Institute of General Medical Sciences.
National Human Genome Research Institute. “Genetics Glossary — Allele.” National Human Genome Research Institute.
NOAA. “Food Webs and the Ocean.” NOAA.
U.S. Geological Survey. “Rock Cycle.” U.S. Geological Survey.

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