Praxis Middle School Science Ultimate Guide and Practice Test
Preparing to take the Middle School Science exam?
You’ve found the right page. We will answer every question you have and tell you exactly what you need to study to pass the Middle School Science exam.
Praxis Middle School Science Quick Facts
The Praxis Middle School Science tests the general science knowledge needed to be an excellent middle school science teacher.
The Middle School Science test consists of 125 selected-response questions. The test is given on a computer. You will have 2.5 hours to complete the exam.
The scores for this test range from 100 to 200. In most states, you need a 150 to pass the test. The exceptions are as follows: Iowa requires a 137, Northern Mariana Islands require a 145, American Samoa requires a 148, and Alabama requires a 151.
In order to pass this test, you need to be familiar with a wide variety of scientific concepts. Depending on how recently you have studied science, it may take more or less time to study for the test. In general, you should allocate a week or two per subsection to ensure adequate review.
What test takers wish they’d known:
- This is a computer-delivered test.
- You will be required to present a photo ID when you take your exam.
- No food, drinks, or cell phones are allowed in the test room. Not all testing centers have lockers, so don’t bring any of these items with you.
Information and screenshots obtained from the ETS Praxis website.
I: Scientific Inquiry, Methodology, Techniques, and History
Scientific notation is how scientists communicate numbers in short form. It is used because scientists often measure very small and very large numbers.
How to put a number into scientific notation:
- Move the decimal place in the number so that there is only one whole number before the decimal point.
- Count the number of places you have moved the decimal. This will be the exponent on your scientific notation.
- If you have moved the decimal point to the right, you use a negative coefficient.
- If you have moved the decimal point to the left, you use a positive coefficient.
- Count the number of places you have moved the decimal. This will be the exponent on your scientific notation.
- Write the number as a single whole number followed by the decimal point and any trailing numbers. Multiply it by 10 to the power of the number of spaces moved.
- Example: Write 621 in scientific notation
- Rewrite as 6.21
- The decimal moved 2 places to the left, so you use a positive exponent of 2.
- In scientific notation, it will be 6.21 x 102
- Rewrite as 6.21
How to convert from scientific notation to standard notation:
- Look at the exponent on the number. If it is positive, move the decimal place to the right by the number of places indicated by the exponent. If it is negative, move the decimal place to the left by the number of places indicated by the exponent.
- Example: Write 5.102 x 107 in standard notation.
- Since the exponent is positive, it is a bigger number and the decimal moves to the right. Rewrite 5.102 so that there are 7 spaces after the decimal. For example: 5.102_ _ _ _. Fill in zeros in the spaces and move the decimal point to the right by those places. 51020000 is 5.102 x 107 in standard notation.
On the exam, you may see answers in scientific notation and have to answer with the correct choice. For example:
Mariana is measuring 897 grams of NaOH. How would this be accurately communicated in scientific notation in her lab report?
- 8.97 x 102 grams
- 8.972 grams
- 8.97 x 10-2 grams
- 897 grams
The correct answer is A. The decimal point moves two places to the left from standard notation to scientific notation. Therefore the exponent is 2. Choice B is incorrect because it is missing the “x 10.” Choice C is incorrect because it is negative. Choice D is the number in standard notation.
Alfred Wegener came up with the theory of continental drift in 1912. This is the idea that the continents are slowly moving around the earth. His theory was initially rejected by many scientists because he was an outsider to the field and didn’t command much respect in the scientific community. Furthermore, his estimates of the speed of drift were approximately 100 times too fast, so the math did not hold up to rigorous analysis. Eventually, however, his theory was accepted as having merit.
Emergency Procedures for Minor Burns
For minor burns, it is important to cool the burn by holding the burned skin under cool running water or applying a cool, wet compress until the pain lessens. If it is a chemical burn, the chemical should be flushed from the skin for at least 10 minutes. Remove any jewelry, such as rings, before the area becomes swollen. Apply a lotion and bandage the burn loosely with sterile gauze.
II. Basic Principles of Matter and Energy
Radioactive decay is a natural process by which an unstable isotope of one element changes into another isotope and releases radiation in the process. It can be of either the same element or a different element. The three most common types of radioactive decay are alpha, beta, and gamma decay.
Alpha decay is the release of an alpha particle from the nucleus; for example, uranium-238 undergoes alpha decay to become thorium-234. Beta-decay is the release of a beta particle from the nucleus, as when carbon-14 undergoes beta decay to become nitrogen-14. Gamma decay is the release of a photon from the nucleus. This does not actually change the identity of the isotope, but it reaches a lower energy state.
Scientists have harnessed the power of radioactive decay through useful applications such as carbon dating of historic artifacts and treatment of cancer. They have also used properties of radioactive decay to create the atomic bomb.
The nitrogen cycle is a process by which atmospheric nitrogen gas (N2) is converted into forms that can be used by plants and animals. Bacteria convert N2 to ammonia (NH3) during nitrogen fixation. This form is usable by plants as a source of growth. Other bacteria further convert NH3 into nitrites (NO2-) and nitrates (NO3-). When plants use these forms of nitrogen, the nitrogen becomes available to animals when they eat the plants. Though animals breathe in atmospheric nitrogen, they cannot use this form of nitrogen in their bodies. Other bacteria, called denitrifying bacteria, convert NO3 back to atmospheric nitrogen.
Humans are also a part of the nitrogen cycle because we use an industrial process to convert N2 into NH3 for use as fertilizer that promotes the growth of plants. Excess fertilizer can run off into streams where it can cause algal blooms and other adverse effects.
Laws of Thermodynamics
The four laws of thermodynamics rule the natural world.
The zeroth law of thermodynamics states that if two systems are in equilibrium with another system, they are also in equilibrium with each other.
The first law of thermodynamics states that energy can’t be created nor destroyed. Energy can only change forms.
The second law of thermodynamics states that the entropy of a system is always increasing. Entropy is a measure of the disorder of a system. Think about it this way: if you never actively clean your room, it becomes messier. The entropy of the system is always increasing.
The third law of thermodynamics states that as temperature approaches absolute zero, entropy approaches zero. Put in other words, objects become more ordered the colder they get. This can be seen in the fact that solids have a crystalline atomic structure while gases flow freely without any true structure.
III: Physical Sciences
Work is what causes things to move or change position. Work is calculated by the equation W = F ∙ d cos𝛳. F is the force applied, d is the displacement, and 𝛳 is the angle between the force and the displacement. Work only occurs in the direction of the movement. Note that if the force vector and the displacement vector are perpendicular to each other, no work happens because cos(90) is 0. Any quantity multiplied by 0 is also 0. The unit of measurement for work is a joule, also known as a newton meter.
Some sample problems are as follows:
How much work is used to push a box up a 5-meter-long ramp angled at 60 degrees with the horizon if a student uses a 15 N force applied horizontally?
W = F ∙ d cos𝛳
= 15 ∙ 5cos(60)
= 15 ∙ (5 ∙ ½)
= 45 joules
How much work is necessary to lift a 10 kg box 10 meters? Assume the force is applied in the direction of movement.
The force which must be applied is 10kg ∙ 10 m/s2 = 100 N.
The distance traveled is 10 meters.
The angle is zero.
W = F ∙ d cos𝛳
W = 100N ∙ 10 meters ∙ cos(0)
W = 100N ∙ 10 meters ∙ 1
W = 1000 joules
Types of Waves and Basic Characteristics
There are several ways to categorize waves.
- Categorize by the direction of the motion:
- Longitudinal waves are waves in which the motion of the particles is in the same direction as the motion of the energy. A sound wave is an example of a longitudinal wave.
- Transverse waves are waves whose motion is perpendicular to the direction of energy movement. For example, a Slinky spring toy moving up and down would represent a transverse wave.
- Surface waves are waves in which the motion of the particles is circular.
- Categorize based on whether they can transmit energy through a vacuum:
- Mechanical waves cannot transmit energy through a vacuum. Examples of this principle include sound waves and water waves.
- Electromagnetic waves can transmit energy through a vacuum. There are several different types of electromagnetic waves, as illustrated below.
Inductiveload, NASA [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]
All waves have common features. Frequency refers to how fast the wave completes a cycle. Amplitude refers to the strength or height of the wave. Wavelength (ƛ) is the distance between corresponding parts of the wave. Speed is how quickly the wave travels. Intensity is the power per area and is used to measure mechanical waves.
Kraaiennest[CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
The frequency of the wave is measured in hertz and is calculated by c/ƛ.
How to Balance Chemical Equations
There are four basic types of chemical reactions.
- Synthesis – when two or more elements or compounds combine into a more complicated compound
- A + B → AB
- Decomposition – when a compound breaks into smaller components
- AB → A + B
- Single replacement – when one element replaces another in a compound
- AB + C → AC + B
- Double replacement – when two elements swap places in two compounds
- AB + CD → AD + CB
All chemical reactions are balanced in that they observe the law of conservation of mass.
How to balance the notation of a chemical reaction:
- Count the number of atoms of each element on both sides of the chemical equation
- Rules for counting atoms
- Coefficients apply to all elements following the coefficient. Example: 2HF has 2 hydrogens and 2 fluorines
- Subscripts apply only to the element immediately preceding them. Examples: H2O has 2 hydrogens and one oxygen. CCl4 has 1 carbon and 4 chlorines.
- Parentheses are used to group polyatomic ions. Polyatomic ions can be balanced as a unit because they are grouped in nature. Pb(NO3)2 has one lead and two nitrate groups.
- Rules for counting atoms
- Determine if anything is imbalanced. If so, make changes to balance atoms.
- Change coefficients in front of compounds to change atom numbers.
- Re-count atoms of each element until there are the same number of atoms of each element on both sides of the equation.
Balance the following equation:
N2 + H2 → NH3
The reactants side has 2 nitrogens and 2 hydrogens. The products side has 1 nitrogen and 3 hydrogens. To balance hydrogen, the least common multiple of 2 and 3 is 6. So place a 3 in front of the reactants hydrogen, and a 2 in front of the products:
N2 + 3H2 → 2NH3
Re-count both sides: everything is balanced! There are 2 nitrogens on each side and 6 hydrogens on each side.
Balance the following equation:
Pb(NO3)2 + NaCl → NaNO3 + PbCl2
The left side has 1 lead, 2 nitrates, 1 sodium, and 1 chlorine. The right side has 1 sodium, 1 nitrate, 1 lead, and 2 chlorines.
Add a 2 in front of NaCl on the left-hand side to balance chlorine:
Pb(NO3)2 + 2NaCl → NaNO3 + PbCl2
Re-count: The left side has 1 lead, 2 nitrates, 2 sodiums, and 2 chlorines. The right side has 1 sodium, 1 nitrate, 1 lead, and 2 chlorines.
Add a 2 in front of NaNO3 on the right to balance sodium:
Pb(NO3)2 + 2NaCl → 2NaNO3 + PbCl2
Re-count: The left side has 1 lead, 2 nitrates, 2 sodiums, and 2 chlorines. The right side has 2 sodiums, 2 nitrates, 1 lead, and 2 chlorines. They’re balanced! You’re done!
There are several laws that describe the behavior of gases.
Boyle’s law states that when the temperature is held constant, pressure is inversely proportional to volume. That means that if you increase the pressure on a gas at a given temperature, the volume will decrease to compensate: P1 x V1 = P2 X V2. In other words, the product of pressure times volume remains constant.
Charles’s law states that the volume and temperature are directly proportional: V1 / T1 = V2 / T2. For example, at constant pressure, a balloon that is adequately inflated with air at room temperature will deflate if placed in a freezer for an extended period of time.
Amonton’s Law (aka Gay-Lussac’s law and Dalton’s law) states that when the volume is held constant, the pressure is proportional to temperature.
There are many terms used to describe solutions. A solution is a mixture in which a solute is dissolved in a solvent. A common everyday solution is saltwater. In saltwater, the solute is the NaCl, while the solvent is water.
There are informal terms related to solutions. A “dilute” solution is weak and doesn’t have much dissolved solid. (The term “dilute” can also be used as a verb, meaning to add more solvent.) A “concentrated” solution is strong and has a large amount of dissolved solute.
The terms saturated, unsaturated, and supersaturated relate to how much solute is dissolved in a given amount of solid. A solution is saturated if it has the maximum amount of solute possible while still remaining stable, an amount that is visually represented on the solubility curve. It is supersaturated if it has more than the maximum stable amount of solute. Supersaturated solutions are created by making the solution at a high temperature and slowly cooling them. A solution is unsaturated if it is below the solubility curve. This means more solute can be added to the solution.
Molarity is the number of moles of solute per liter of solution.
Molality is the number of moles of solute per kilogram of solvent.
IV: Life Sciences
Human Nervous System
The nervous system is responsible for the control of different parts of the body. The nervous system is responsible for both voluntary processes, such as movement and thought, and involuntary processes, such as breathing and the beating of the heart.
The nervous system consists of nerve cells that transmit messages from control systems in the brain to the rest of the body. In terms of organization, the simplest components of the nervous system are neurons, which are bundled into sheaths called nerves. Nerves are held together with glial cells, which support the neurons. Neurons can be sensory neurons, which gather information, or motor neurons, which transmit messages from the central nervous system to the body. The brain is the most complex organ of the nervous system.
Structurally there are two parts of the nervous system. The central nervous system consists of the brain, spinal cord, and nerves. The central nervous system controls most of the functions of the body. The peripheral nervous system consists of sensory neurons and parts that connect it with the central nervous system. The peripheral nervous system provides input to the central nervous system about what is going on in the body.
There are also two portions of the nervous system in terms of function: the somatic and autonomic components. The somatic component comprises the voluntary functions of the nervous system, such as moving and thinking. The autonomic component controls automatic processes, such as breathing and blood pressure.
Mitosis and Meiosis
All somatic (body) cells in the human body have 46 chromosomes. They are considered diploid because there are two copies of each chromosome. Cells in the body undergo mitosis to make exact copies to replace themselves. DNA is replicated during interphase, which happens before formal cell division. At this point in time, the cell contains double the normal amount of DNA. Then mitosis commences.
- Prophase – The DNA condenses into chromosomes and the centromere appears. The nucleus begins to disappear. The spindle apparatus responsible for pulling the DNA apart appears.
- Metaphase – The chromosomes line up on the midline of the cell.
- Anaphase – The chromosomes are pulled apart by the spindle apparatus. The chromosomes are on two different sides of the cell.
- Telophase – Two new cells begin to appear. New nuclear envelopes appear.
Mysid [Public domain]
Meiosis occurs only in sex cells. The goal of meiosis is to create cells with half the amount of genetic material (23 chromosomes) for sexual reproduction. In females, the result of meiosis is an egg cell and three smaller nonfunctional polar bodies. In males, the result of meiosis is four sperm cells.
Meiosis is like repeated mitosis. During the first cell division, chromosomes cross over during prophase. This allows for the shuffling of genetic materials. After meiosis I, the result is two non-identical diploid daughter cells. These two daughter cells divide further to make four non-identical haploid sex cells. Haploid sex cells contain 23 chromosomes each.
National Institutes of Health [Public domain]
Watson and Crick
James Watson and Francis Crick discovered the structure of DNA. In the 1950s they proposed that DNA has a double helix structure: a spiral of two strands of DNA that can be unwound for replication and translation of DNA sequences into protein.
DNA has a sugar phosphate “backbone.” In the middle are nucleic acids that bond to their partner on the other strand. The elements of base pairs are adenine, which bonds to thymine, and cytosine, which bonds to guanine. Since the base pairs have set partners, it is possible to replicate both sides of the strand with just one known side. For example: What is the corresponding strand to the sequence AATTCG? It would be TTAAGC, since A bonds with T and C bonds with G.
Trophic levels can be thought of as levels of the food chain. At the bottommost level are the autotrophs or primary producers, followed by primary consumers, secondary consumers, and tertiary consumers.
Food webs can be created from the trophic levels. In a food web, the arrow always points in the direction of energy flow; that is, from who is being eaten to who is doing the eating. Since the base of the entire trophic system is plants, if there is a drought, many plants will die. This means there isn’t as much food for the primary consumers, so there will be fewer of them. This trickles up the entire food chain, affecting all species.
V: Earth and Space Sciences
Weathering, Erosion, Deposition (W.E.D.)
Weathering is the process by which rocks are broken into smaller pieces. Weathering can be physical or chemical. Physical weathering includes plants and animals breaking rocks into smaller pieces; freezing and thawing, which expands cracks in rocks; and wind or sand causing abrasion. Chemical weathering includes acid rain, oxidation such as rusting, and water dissolving rocks.
Erosion is the movement of these smaller rock pieces to another location. Erosion can be caused by wind, water, waves, gravity, or glaciers. (WWWGG)
Deposition describes the rocks being dropped in a new place.
The Earth is composed of four layers. From the outside going inward: the crust, mantle, outer core, and inner core. The crust is the part that we live on and is made of solid plates that slowly move. The mantle is a molten layer on which the crust “floats”; it is made of molten rocks that slowly flow. Past the mantle is the outer core, which is liquid iron and nickel and creates Earth’s magnetic field. The innermost part of the Earth is the inner core, which is solid nickel and iron.
The tides are influenced by the Sun and the Moon’s gravitational pull. The tides change throughout the day, and high tide and low tide each happen once every 24 hours. As the Moon revolves around the Earth, its gravitational field affects the oceans, creating the tides. Whatever point on Earth the Moon is closest to will experience high tide, and the point on the opposite side of Earth will be experiencing high tide as well. The sides of the Earth that are perpendicular to the Moon’s location experience low tide.
The Sun can play a role in the tides as well. When the Sun and Moon are aligned with the Earth, the result it is referred to as a spring tide, and the high tides are the highest and the low tides are the lowest for the month. This occurs when there is a new moon or full moon.
The other named tide is a neap tide, which occurs during a first or third quarter moon phase, when the Sun and Moon are perpendicular to each other with the Earth at the meeting point. This causes the least difference between the high and low tide.
Hubble Space Telescope
The Hubble space telescope was launched into space in 1990. It was the first major optical space telescope and has provided images that are not obstructed by light or atmospheric pollution. There have been five missions to service the telescope, which remains in orbit today.
The Hertzsprung-Russell diagram is a scatter plot that shows the relationship between a star’s color, temperature, and brightness or luminosity. Temperature is listed across the x axis and decreases from left to right (the opposite of most graphs). Luminosity or brightness is listed on the y-axis. The groupings on the diagram help define the stars’ color and life span. Typically, the larger a star is, the less time it has to live.
VI: Science, Technology, and Society
Sources of Power
Geothermal energy is from heat within the Earth. The heat is used to boil water and produce steam, which turns turbines that create energy that can be stored. Geothermal plants are challenging to build because finding locations where the Earth’s heat can be accessed is difficult. Additionally, there are greenhouse gases deep within the Earth that can rise to the surface and be released.
Another energy source is nuclear energy, which produces a lot of energy, but releasing the energy and storing the waste is dangerous. Nuclear energy is created similarly to geothermal energy, except that the heat comes from splitting an atom.
Hydroelectric energy uses water to spin a turbine and capture energy. It is generally created by building a dam, which is expensive and causes significant changes to the environment. Water can be run through the turbines repeatedly, making it a renewable energy source.
Solar energy uses panels to capture the Sun’s energy, which can then be stored until it is needed. Solar panels are expensive and require a lot of sunlight to capture enough energy.
Fossil fuels include gas, coal, oil, and natural gas. These are non-renewable resources that take millions of years to form, so they are not easily replaced. They are inexpensive compared to the other sources, and so they are commonly used. They also cause pollution as they produce carbon emissions when burned.
Genetically Modified Crops
Genetically modified crops (GMOs) are agricultural products that scientists have changed through the use of genetic technology. Crops with specific traits (e.g., resistance to disease, better taste, or greater longevity after being picked) t can be cross-pollinated to create a more desirable crop. Cotton, corn, and soy are common examples of GMOs.
There are concerns associated with GMOs. One concern is that as more of the organisms become modified, the original organisms’ DNA will become extinct. There are also concerns about pesticide use. As crops are created that do not require as many pesticides, there are more insects, which impacts the environment.
Invasive species are organisms that are not native to the ecosystem they are a part of. They do not have to come from a foreign country and can come from a nearby ecosystem. They can be bacteria, plants, animals, or any living organism.
For example, cane toads were brought into Australia to prey on a beetle species as a natural form of insecticide. Because the cane toads were not native to Australia, they didn’t have any natural predators, and their population grew out of control. This growth put a strain on the ecosystem as the toads use resources for shelter, food, and water.
And that’s some basic info about the test.