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Free PRAXIS II Science Study Guide: Basic Principles


How to Pass the Science PRAXIS II Test | Practice PRAXIS II Questions | Science PRAXIS II Study Guide

This PRAXIS II study guide specifically covers the basic principles portion of the PRAXIS II Middle School Science (0439) and PRAXIS II General Science: Content Knowledge (0435) exams.

Here you'll find practice PRAXIS questions and detailed information about scientific methodology and philosophy, measurement, data collection, laboratory procedures and safety, atomic and nuclear structure, matter, energy, heat and thermodynamics.

Since the PRAXIS II science exams measure your knowledge of so many scientific topics, this free PRAXIS II study guide is split into four parts. Check out the links below to visit the life sciences, earth and space sciences, chemistry and physics portions of this free PRAXIS II study guide!

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100% Original Content

I created this study guide when preparing to take the PRAXIS II Middle School Science (0439) exam. I used a variety of sources to research these topics and rewrote what I learned in my own words. No part of this study guide has been copied from Wikipedia or any other source.

Official PRAXIS II Study Guides - Study guides specifically written to help you pass the PRAXIS II exam!


Scientific Methodology and Philosophy

Scientific Method, Facts, Models, Theories, Laws, Experimental Design and Science History

A. Demonstrate understanding of scientific methods of problem solving

  • THE SCIENTIFIC METHOD: techniques used for the investigation of phenomena
    • (1) collection of scientific facts through observation and measurement
    • (2) development of one or more hypotheses
    • (3) execution of experiments to test the hypotheses
    • (4) analysis of collected data
    • (5) acceptance, modification or rejection of the model based on extensive testing

B. Distinguish among scientific facts, models, theories and laws

  • FACT: an observation that has been repeatedly confirmed and accepted as true
  • MODEL: a scientific statement that has some experimental validity or is only accurate under limited conditions
  • THEORY: an accepted hypothesis that explains "why" something occurs; valid only if no evidence exists to disprove it; i.e. theory of evolution
  • LAW: summarizes a body of observations; can explain and predict things but not why they happened; have uniformity; universal; i.e. law of gravity

C. Use science process skills in experiments and investigations, and to solve problems

  • Ask a question
  • Do research
  • Form a hypothesis
  • Design an experiment
  • Make observations
  • Draw a conclusion

D. Demonstrate understanding of experimental design

  • EXPERIMENTAL DESIGN: the design of all information-gathering exercises where variation is present
    • (1) select the problem (state vs. process/change: descriptive, exploratory, predictive, hypothesis-testing)
    • (2) identify dependent variables
    • (3) identify independent variables
    • (4) determine the number of levels of independent variables
    • (5) identify all possible combinations
    • (6) determine number of observations
    • (7) redesign
    • (8) randomization
    • (9) meet ethical/legal requirements
    • (10) mathematical model
    • (11) data collection
    • (12) data reduction
    • (13) data verification

E. Demonstrate knowledge of the historical roots of science

  • Important Historical Figures: Einstein, Bohr, Curies, Mendel, Darwin, Watson and Crick, Newton, Copernicus, Galileo, Hutton, Mendeleev, Dalton
  • Landmark Events and Discoveries: DNA structure (the double helix), theory of evolution (all life is related and descended from a common ancestor), radioactivity (particles which are emitted from nuclei as a result of nuclear instability), atomic structure (the atom is the basic unit of matter), Newton's Laws of Motion (classical mechanics), the Big Bang Theory (the origin of the universe)

F. Demonstrate understanding of the unified, integrative nature of the various disciplines and concepts in science

  • SCIENTIFIC DISCIPLINES: earth/space sciences (astronomy, geology, etc.); life sciences (biology, physiology, etc.); physical sciences (physics, chemistry, etc.);
Scientific Measurement

Scientific Measurement

Scientific Mathematics, Measurement & Data Manipulation

Scientific Measurement, Data Collection, Tables, Graphs, Charts and Sources of Error

A. Demonstrate understanding of scientific measurement and notation systems

  • ACCURACY: the closeness of a measurement to its true value
  • PRECISION: the degree to which repeated measurements show the same results
  • UNITS: 1 Mu = 1,000,000 u ... 1 ku = 1000 u ... 100 cu = 1 u ... 1000 mu = 1 u
  • SIGNIFICANT FIGURES: all non-zero digits (i.e. 91 = 2 significant figures); zeros located between non-zero digits (i.e. 101 = 3 significant figures); all zeros located after the first non-zero (i.e. 120.00 = 5 significant figures); N only if the number is in scientific notation; zeros located before the first non-zero are not significant (i.e 0.0013 = 2 significant figures);

B. Demonstrate understanding of processes involved in scientific data collection, manipulation, interpretation, and presentation

C. Interpret and draw conclusions from data, including those presented in tables, graphs, maps, and charts

D. Identify and demonstrate an understanding of sources of error in data that is presented

Laboratory Equipment

Laboratory Equipment

Laboratory Procedures & Safety

Laboratory Materials, Procedures and Safety

A. Demonstrate understanding of procedures for safe preparation, storage, use, and disposal of laboratory and field materials

B. Identify laboratory and field equipment appropriate for scientific procedures

C. Demonstrate knowledge of safety and emergency procedures for the science classroom and laboratory


Basic Principles: Matter & Energy

Matter, Elements, Physical & Chemical Changes, Conservation of Mass & Energy and Energy Transformations

A. Demonstrate understanding of the structure and properties of matter

  • PROPERTIES: matter is anything that has mass and volume
    • MASS: the amount of matter that makes up an object (constant)
    • VOLUME: the amount of space an object takes up
    • WEIGHT: the measure of the force of gravity on the mass of an object (mass x gravity); measured in newtons;
  • STRUCTURE: all matter is composed of atoms, the basic unit of molecular structure
    • ATOMS: the smallest particle of an element that retains the chemical properties of that element
  1. composed of a nucleus made of protons (+ charge) and neutrons (neutral) as well as a cloud of electrons (- charge)
  2. elements contain only one type of atom and each element contains a different atom
  3. an atom's number of protons (aka "atomic number") give the element its identity
  4. all atoms contain the same number of protons and electrons
  5. all atoms of a certain element contain the same number of protons

ISOTOPES: atoms of the same element that contain different amounts of neutronsB. Demonstrate understanding of the factors that influence the occurrence and abundance of the elements

C. Distinguish between physical and chemical changes of matter

  • PHYSICAL CHANGES: a change that may affect density, pressure, temperature and/or other physical properties; does not alter the chemical formula; i.e. solid > liquid > gas
  • CHEMICAL CHANGES: a change that alters the chemical formula; occurs on the molecular level; i.e. water > hydrogen peroxide

D. Demonstrate understanding of the conservation of mass/energy

  • LAW OF CONSERVATION OF ENERGY: states that the total amount of energy in a closed system (a system in which no energy can escape or be introduced) remains constant over time; the energy may take various forms (kinetic, light, heat, etc.) but it cannot be created or destroyed;
    • Example: while a box is hanging motionless from a string, it has gravitational potential energy; when the string is cut, that potential energy becomes kinetic energy; when the box hits the ground, that kinetic energy becomes sound and heat;
  • LAW OF CONSERVATION OF MASS: the mass of a closed system will remain constant over time; mass cannot be created or destroyed; mass can be rearranged in space and altered to contain different particles;

E. Demonstrate understanding of energy transformations

  • ENERGY: the ability to do work
  1. HEAT: the effect of moving molecules within matter; increased motion = increased heat; most easily dissipated form of energy;
  2. LIGHT: caused by the motion of light waves
  3. SOUND: caused by the motion of sound waves; also easily lost
  4. ELECTRICAL: the effect of moving electrical charges from one point to another within a conductor
  5. CHEMICAL: energy stored in the chemical bonds that hold atoms and ions together
  6. NUCLEAR: energy stored in the nucleus of an atom; released when nuclei are split apart (fission) or combined (fusion);
  7. MECHANICAL: the sum of the kinetic and potential energy present in a mechanical system
  • KINETIC: the energy matter possesses due to its motion
  • POTENTIAL: the energy matter possesses due to its position or shape

ENERGY TRANSFORMATION: the process of changing energy from one form to another

  • Examples: flashlight = chemical > light; television = electrical > light, sound, heat; telephone = sound > electrical/electromagnetic > sound; engine = chemical > kinetic, heat, sound;

Basic Principles: Heat & Thermodynamics

Heat, Temperature, Thermal Energy and the Laws of Thermodynamics

A. Distinguish between heat and temperature

  • HEAT: a measure of how much thermal energy is transferred from one body to another
  • TEMPERATURE: a measure of the average kinetic energy of the molecules that make up a substance

B. Demonstrate understanding of measurement, transfer, and effects of thermal energy on matter

    • KELVINS: the unit (K) in which temperature is measured; an absolute measure of temperature designed so that temperatures are always positive (0K = the lowest theoretical temperature a material can have; 273K = water freezes; 373K = water boils)
    • DEGREES CELSIUS: another unit (*C) in which temperature is measured
    • CALORIES: the unit (cal) in which heat is measured; the amount of heat needed to raise the temperature of one gram of water by one degree Celsius; 1 cal. = 1 g/*C = 4.19 Joules (J)
    • THERMAL EQUILIBRIUM: when two objects of different temperatures come into contact, heat will flow from the hotter object to the colder one until both have the same temperature; heat lost by the hotter object = heat gained by the colder;
    • LATENT HEAT OF TRANSFORMATION: the amount of heat required to change the phase of a substance
    • SPECIFIC HEAT: the amount of heat required to raise the temperature of a certain mass of a given substance; constant
      • (1) Conduction: transfer of heat by intermolecular collisions; molecules transfer their kinetic energy to each other
      • (2) Convection: involves the molecules themselves moving from one place to another; typically involves gases; i.e. a fan displacing hot air with cold air;
      • (3) Radiation: takes place when the source of heat is some form of electromagnetic wave, such as a microwave or sunlight; the waves transfer heat; i.e. microwave ovens energize food particles with microwave radiation;

C. Solve quantitative problems dealing with the measurement and transfer of thermal energy

D. Demonstrate understanding of the First and Second Laws of thermodynamics

  • FIRST LAW OF THERMODYNAMICS: the internal energy of a system increases if heat is added to the system or if work is done on the system and decreases if the system gives off heat or does work; similar to the law of conservation of energy; the flow of heat is an energy transfer;
  • SECOND LAW OF THERMODYNAMICS: (1) heat flows spontaneously from a hotter object to a colder one (i.e. ice cream does not get colder); (2) no machine is 100% effective (i.e. all machines generate heat and some of that heat is always lost to its surroundings); (3) ordered systems are liable to fall into disorder (i.e. salt and pepper can be easily mixed but not separated); disorder (aka entropy) is what gives time its direction

Basic Principles: Atomic & Nuclear Structure

Atomic Models, Atomic & Nuclear Structure, Atoms and Nuclear Reactions

A. Demonstrate understanding of atomic models and their experimental bases

  • RUTHERFORD MODEL: In 1909, Rutherford conducted a gold foil experiment that disproved J.J. Thomson's "plum pudding" theory of subatomic structure, which stated that an atom's mass is spread equally throughout. Rutherford fired a beam of alpha particles at a thin gold foil and discovered that rather than passing through the foil, some particles were deflected. In 1911, he proposed a model in which the atom is composed of a tiny, dense core of positively charged protons (which contains nearly all of the atom's mass) and a swirling ring of electrons.
  • BOHR MODEL: In 1913, Bohr studied the line spectra phenomena and hypothesized that electrons do not move freely within an atom. He proposed a planetary model in which electrons orbit the nucleus in defined, spherical orbits called energy levels or electron shells. He also hypothesized that electrons could move between these shells when energy is absorbed or emitted.
  • QUANTUM MECHANICAL MODEL: a modern atomic model that states that it is impossible to determine the precise location of an electron. Instead of moving within defined shells, electrons travel in diffuse clouds called orbitals. The position of an electron is described using the quantum numbers n (principal energy level), l (shape of the orbital), ml (relative orientation of the orbital) and ms (spin).

B. Demonstrate understanding of atomic and nuclear structure and forces


C. Relate electron configuration to the chemical and physical properties of an atom

  • ELECTRON CONFIGURATION: the configuration of electrons within an atom
    • Electrons reside in the orbitals, which are found in the sublevels (s, p, d, f) of the principal energy levels (n = 1, 2, 3, 4); orbitals contain a maximum of two electrons, which must be of opposite spin;
    • The electron configuration of an atom is notated by a series of orbital labels and can be determined using the periodic table
    • VALENCE ELECTRONS: electrons which inhabit the outermost shell of an atom; can be determined by an element's periodic group notation (IA = 1 valence electron, IIA = 2 valence electrons, etc.); atoms with the same number of valence electrons - and which are thus located in the same group - have similar chemical and physical properties;

D. Demonstrate knowledge of characteristics of radio-isotopes and radioactivity (for example, half-life)

  • RADIO-ISOTOPES: Unstable isotopes that release radiation. Radio-isotopes include all elements with atomic numbers greater than 83. Not all isotopes are radio-isotopes.
  • ISOTOPES: atoms of the same element that contain different amounts of neutrons
  • RADIOACTIVITY: When energy and matter are released due to a change in the nucleus of an atom.
  • HALF-LIFE: The length of time it takes for half of a particular substance to decay.

E. Identify products of nuclear reactions

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