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MTEL General Science (64) study materials
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MTEL General Science (64) practice questions

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Question 1General Science content domains (not enumerated in source)

A student observes that a balloon rubbed on wool attracts small paper bits. Which statement best explains this observation in terms of electric charge?

  1. The rubbing transfers electrons, giving the balloon a net static charge that polarizes the paper. Correct answer.
  2. The rubbing transfers protons from the wool to the balloon, charging it positively.
  3. The balloon becomes magnetic and attracts the paper through magnetic force.
  4. The rubbing creates new electric charges inside the balloon through friction.

Explanation

Friction between wool and rubber transfers electrons, leaving the balloon with a net static charge. This charged balloon polarizes neutral paper molecules, producing an attractive force. Charge is conserved and moved, not created, and magnetism is not the cause here.

Question 2General Science content domains (not enumerated in source)

Which statement correctly describes the relationship between a cell's DNA, its genes, and its proteins?

  1. Genes are made of proteins that store the instructions for making DNA.
  2. Genes are segments of DNA that encode instructions for assembling proteins. Correct answer.
  3. DNA is made of proteins that determine the sequence of genes.
  4. Proteins are segments of DNA that encode instructions for assembling genes.

Explanation

A gene is a specific segment of DNA whose sequence specifies the order of amino acids in a protein. DNA is the hereditary molecule, and proteins are the products built from the instructions. This direction of information flow is central to molecular genetics.

Question 3General Science content domains (not enumerated in source)

A sealed container holds a fixed mass of gas. If the gas is heated while its volume is held constant, what happens to the pressure and why?

  1. Pressure increases because the molecules strike the walls more often and with greater force. Correct answer.
  2. Pressure stays the same because the number of gas molecules is unchanged.
  3. Pressure increases because the gas molecules themselves expand in size when heated.
  4. Pressure decreases because the molecules occupy more space at higher temperature.

Explanation

At constant volume, raising the temperature increases the average kinetic energy of the gas molecules. They collide with the container walls more frequently and with greater momentum change, so pressure rises. The number of molecules is fixed, but their motion changes.

Question 4General Science content domains (not enumerated in source)

Which rock type forms primarily from the cooling and solidification of molten material?

  1. Igneous rock Correct answer.
  2. Sedimentary rock
  3. Clastic rock
  4. Metamorphic rock

Explanation

Igneous rocks crystallize from magma or lava as it cools. Sedimentary rocks form from deposited and lithified material, and metamorphic rocks form from existing rocks altered by heat and pressure. Clastic rock is a category of sedimentary rock.

Question 5General Science content domains (not enumerated in source)

During photosynthesis, a plant converts carbon dioxide and water into glucose and oxygen. Which statement best summarizes the energy transformation involved?

  1. Heat energy from the environment is converted directly into glucose.
  2. Light energy is captured and stored as chemical energy in glucose. Correct answer.
  3. Electrical energy from the soil is stored as chemical energy in water.
  4. Chemical energy in glucose is converted into light energy.

Explanation

Photosynthesis uses light energy absorbed by chlorophyll to drive reactions that build glucose, storing energy in chemical bonds. Oxygen is released as a byproduct. This is the reverse of the energy release that occurs during cellular respiration.

Question 6General Science content domains (not enumerated in source)

An object is pushed with a constant net force. According to Newton's second law, what happens to its acceleration if the net force is doubled while the mass stays the same?

  1. The acceleration doubles. Correct answer.
  2. The acceleration is halved.
  3. The acceleration is quartered.
  4. The acceleration stays the same.

Explanation

Newton's second law states that acceleration equals net force divided by mass. With mass constant, acceleration is directly proportional to net force, so doubling the force doubles the acceleration. Halving would occur if the mass were doubled instead.

Question 7General Science content domains (not enumerated in source)

Which process directly produces gametes with half the usual chromosome number in animals?

  1. Binary fission
  2. Meiosis Correct answer.
  3. Mitosis
  4. Fertilization

Explanation

Meiosis is a reduction division that halves the chromosome number, producing haploid gametes. Mitosis produces genetically identical diploid cells for growth and repair. Fertilization restores the diploid number by combining two gametes.

Question 8General Science content domains (not enumerated in source)

Which statement best describes the role of decomposers in an ecosystem?

  1. They permanently remove nutrients from the ecosystem.
  2. They convert sunlight directly into usable energy for other organisms.
  3. They break down dead organisms and recycle nutrients back into the environment. Correct answer.
  4. They are the primary consumers that eat living producers.

Explanation

Decomposers such as bacteria and fungi break down dead organic matter, releasing nutrients that producers can reuse. This recycling keeps nutrients available within the ecosystem. They do not produce energy from sunlight or consume living producers as herbivores do.

Question 9General Science content domains (not enumerated in source)

A solution has a hydrogen ion concentration of 1 × 10⁻³ M. What is its pH, and is it acidic or basic?

  1. pH 3, which is basic
  2. pH 11, which is basic
  3. pH 3, which is acidic Correct answer.
  4. pH 11, which is acidic

Explanation

pH is the negative base-10 logarithm of the hydrogen ion concentration, so pH = 3. Values below 7 indicate an acidic solution. A pH of 11 would correspond to a hydrogen ion concentration of 1 × 10⁻¹¹ M and would be basic.

Question 10General Science content domains (not enumerated in source)

In a cross between two heterozygous pea plants (Tt × Tt), where T is tall and t is short, what fraction of the offspring is expected to be short?

  1. All of the offspring
  2. Three quarters
  3. One half
  4. One quarter Correct answer.

Explanation

A Tt × Tt cross yields genotypes TT, Tt, Tt, and tt in equal proportions. Only the tt genotype expresses the recessive short trait, so one quarter of the offspring are expected to be short. Three quarters would show the dominant tall trait.

Question 11General Science content domains (not enumerated in source)

A block slides across a rough horizontal surface and gradually slows to a stop. Which statement best describes the energy transformation?

  1. Thermal energy is converted into kinetic energy by friction.
  2. Kinetic energy is converted into thermal energy by friction. Correct answer.
  3. Kinetic energy is destroyed completely with no other form produced.
  4. Potential energy is converted into kinetic energy with no losses.

Explanation

Friction does negative work on the sliding block, converting its kinetic energy into thermal energy in the block and surface. Energy is conserved overall, so it is transformed rather than destroyed. The block slows because kinetic energy decreases.

Question 12General Science content domains (not enumerated in source)

Which feature of Earth's interior is primarily responsible for generating its magnetic field?

  1. Circulation of water in the oceans
  2. Rotation of the solid inner core alone
  3. Movement of tectonic plates in the crust
  4. Convection of molten iron in the outer core Correct answer.

Explanation

Earth's magnetic field is generated by the geodynamo: convection of electrically conducting molten iron in the outer core, combined with the planet's rotation. This moving conductor produces electric currents that create the field. The inner core is solid, and crustal or oceanic motion does not drive the main field.

Question 13General Science content domains (not enumerated in source)

Two clear liquids are mixed and the mixture becomes warm while a solid precipitate forms. Which conclusion is best supported?

  1. No change occurred because both original liquids were clear.
  2. The precipitate is one of the original liquids that froze.
  3. A chemical reaction occurred, releasing energy and forming a new insoluble product. Correct answer.
  4. A physical change occurred because the liquids simply mixed.

Explanation

Formation of a precipitate and release of heat are both evidence of a chemical reaction. A new insoluble product formed, and energy was released to the surroundings. Simple mixing of liquids without new products would not produce these changes.

Question 14General Science content domains (not enumerated in source)

Which statement best explains why coastal areas often have smaller temperature swings between day and night than inland areas?

  1. Coastal areas receive less sunlight than inland areas.
  2. Water has a higher specific heat than land, so it absorbs and releases heat more gradually. Correct answer.
  3. Water has a lower specific heat than land, so it changes temperature quickly.
  4. Ocean currents stop all heat transfer along the coast.

Explanation

Water's high specific heat means it gains and loses heat slowly, moderating coastal temperatures. Land heats and cools quickly, producing larger day-night swings inland. This difference drives sea and land breezes as well.

Question 15General Science content domains (not enumerated in source)

A mutation changes a single DNA base in a gene, but the resulting protein has the same amino acid sequence. What is the best explanation?

  1. The mutation changed the reading frame but not the protein.
  2. The ribosome corrected the mutation during translation.
  3. The mutation was silent because the genetic code is redundant and different codons can specify the same amino acid. Correct answer.
  4. The mutation must have occurred in a noncoding region of the chromosome.

Explanation

The genetic code is degenerate, meaning several codons encode the same amino acid. A base substitution can therefore change a codon without changing the amino acid, producing a silent mutation. A frameshift would usually alter many amino acids downstream.

Question 16General Science content domains (not enumerated in source)

Which observation provides the strongest evidence that a population of insects has evolved resistance to an insecticide?

  1. Individual insects learn to avoid the insecticide after being exposed once.
  2. The proportion of resistant individuals increases over successive generations after repeated spraying. Correct answer.
  3. Some insects survive a single spraying because they happened to be in sheltered locations.
  4. The insecticide loses potency because it degrades in sunlight over time.

Explanation

Evolution by natural selection requires heritable change across generations. A rising proportion of resistant individuals after repeated exposure shows that resistant traits are being selected for and inherited. Single-generation survival or learned avoidance does not demonstrate evolutionary change.

Question 17General Science content domains (not enumerated in source)

A circuit contains a 12-volt battery connected to a 4-ohm resistor. What current flows through the resistor?

  1. 16 amperes
  2. 3 amperes Correct answer.
  3. 48 amperes
  4. 0.33 ampere

Explanation

Ohm's law states that current equals voltage divided by resistance, so 12 V ÷ 4 Ω = 3 A. Multiplying voltage by resistance gives the wrong quantity, and dividing resistance by voltage is also incorrect. The current is the charge flow per second driven by the voltage.

Question 18General Science content domains (not enumerated in source)

Which sequence correctly orders the levels of biological organization from smallest to largest?

  1. Cell → tissue → organ → organ system → organism Correct answer.
  2. Cell → organ → tissue → organ system → organism
  3. Organ → tissue → cell → organ system → organism
  4. Tissue → cell → organ → organism → organ system

Explanation

In multicellular organisms, cells group into tissues, tissues form organs, organs work together in organ systems, and organ systems make up the organism. This hierarchy reflects increasing complexity. Each level builds on the one before it.

Question 19General Science content domains (not enumerated in source)

A sample of an unknown element has an atomic number of 17 and a mass number of 35. How many neutrons are in one atom?

  1. 52
  2. 18 Correct answer.
  3. 35
  4. 17

Explanation

The number of neutrons equals the mass number minus the atomic number, so 35 − 17 = 18 neutrons. The atomic number gives the number of protons, which is 17 for this element. The sum of protons and neutrons gives the mass number.

Question 20General Science content domains (not enumerated in source)

Which statement best explains why the Moon shows phases as seen from Earth?

  1. Earth's shadow falls on different parts of the Moon each night.
  2. The Moon produces its own light that dims and brightens cyclically.
  3. The changing angle between Earth, the Moon, and the Sun changes how much of the Moon's sunlit side faces Earth. Correct answer.
  4. The Moon physically changes shape throughout the month.

Explanation

The Moon is always half illuminated by the Sun, but the fraction of that lit side visible from Earth changes as the Moon orbits. This changing geometry produces the phases. Earth's shadow causes eclipses, not the regular monthly phases.

Question 21General Science content domains (not enumerated in source)

A car travels 150 meters in 10 seconds and then 300 meters in 20 seconds. What is its average speed over the entire trip?

  1. 45 meters per second
  2. 10 meters per second
  3. 15 meters per second Correct answer.
  4. 20 meters per second

Explanation

Average speed is total distance divided by total time. The total distance is 450 meters and the total time is 30 seconds, giving 15 m/s. Averaging the two segment speeds without weighting by time can mislead.

Question 22General Science content domains (not enumerated in source)

In a food web, a hawk eats snakes, snakes eat mice, and mice eat seeds. If the seed-producing plants decline sharply, which prediction is most consistent with trophic-level reasoning?

  1. The snake population will be unaffected because snakes do not eat seeds directly.
  2. Energy transfer between trophic levels will become more efficient as populations shrink.
  3. The hawk population will immediately increase because competition for food decreases.
  4. Populations at higher trophic levels will decline because less energy is available to support them. Correct answer.

Explanation

Energy flows from producers to consumers, and only a fraction passes to each higher level. If producers decline, less energy is available throughout the food chain, so consumers at all higher levels are eventually affected. Indirect effects propagate up the trophic levels.

Question 23General Science content domains (not enumerated in source)

A buffer solution resists large pH changes when a small amount of strong acid is added. Which property of the buffer best explains this behavior?

  1. It has no dissolved ions, so added acid cannot react.
  2. It has a very high concentration of hydrogen ions that repels added acid.
  3. It contains a weak acid and its conjugate base that can neutralize added acid or base. Correct answer.
  4. It contains only strong acid, which prevents any change in pH.

Explanation

A buffer contains a weak acid and its conjugate base in equilibrium. Added strong acid is consumed by the conjugate base, while added base is consumed by the weak acid, so pH changes only slightly. A solution of only strong acid would not buffer.

Question 24General Science content domains (not enumerated in source)

A population of birds on an island has beak sizes that vary. During a drought, only large, hard seeds remain available. Over several generations, average beak size increases. Which mechanism best explains this outcome?

  1. Genetic drift, because beak size changes randomly regardless of seed type.
  2. Disruptive selection, because both small and large beaks are favored equally.
  3. Directional selection, because one extreme of the trait distribution is favored. Correct answer.
  4. Stabilizing selection, because intermediate beak sizes are favored.

Explanation

When large beaks confer an advantage in cracking hard seeds, birds at that extreme survive and reproduce more, shifting the population mean. This is directional selection. Stabilizing selection would favor intermediate sizes, and disruptive selection would favor both extremes while disfavoring the middle.

Question 25General Science content domains (not enumerated in source)

Two identical resistors are connected in parallel across a battery. Compared with connecting the same two resistors in series, what is true about the parallel arrangement?

  1. The equivalent resistance is lower, so the total current drawn from the battery is higher. Correct answer.
  2. The equivalent resistance is the same, so the current is unchanged.
  3. The equivalent resistance is lower, so the total current drawn is lower.
  4. The equivalent resistance is higher, so the total current drawn is lower.

Explanation

In parallel, the total resistance is less than either individual resistor because there are multiple paths for current. Lower equivalent resistance at the same battery voltage means a larger total current, by Ohm's law. In series, resistances add and current is smaller.

Question 26General Science content domains (not enumerated in source)

Which type of rock forms when molten material cools and solidifies beneath Earth's surface?

  1. Extrusive igneous rock
  2. Metamorphic rock
  3. Sedimentary rock
  4. Intrusive igneous rock Correct answer.

Explanation

Igneous rocks form from cooling magma or lava. When the cooling occurs slowly underground, the resulting coarse-grained rock is called intrusive igneous rock, such as granite. Extrusive rocks form at the surface where cooling is rapid.

Question 27General Science content domains (not enumerated in source)

A student observes that a sample of gas in a rigid sealed container exerts a pressure of 100 kPa at 300 K. If the gas is heated to 600 K, what pressure will it exert, assuming the volume and amount of gas stay constant?

  1. 50 kPa
  2. 400 kPa
  3. 200 kPa Correct answer.
  4. 300 kPa

Explanation

For a fixed amount of gas at constant volume, Gay-Lussac's law states that pressure is directly proportional to absolute temperature (P1/T1 = P2/T2). Doubling the Kelvin temperature from 300 K to 600 K doubles the pressure from 100 kPa to 200 kPa.

Question 28General Science content domains (not enumerated in source)

Which statement correctly describes what happens to the chromosomes during meiosis but not during mitosis?

  1. Homologous chromosomes pair and then separate Correct answer.
  2. Sister chromatids are pulled to opposite poles
  3. The nuclear envelope breaks down
  4. DNA is replicated before division begins

Explanation

Meiosis includes a reductional division in which homologous chromosomes pair (synapsis) and then separate into different cells, halving the chromosome number. Mitosis separates sister chromatids but keeps homologous pairs together in the same cell.

Question 29General Science content domains (not enumerated in source)

Which type of chemical bond results from the electrostatic attraction between oppositely charged ions?

  1. Covalent bond
  2. Metallic bond
  3. Ionic bond Correct answer.
  4. Hydrogen bond

Explanation

An ionic bond forms when one atom transfers electrons to another, creating cations and anions that attract each other electrostatically. This contrasts with covalent bonding, in which electrons are shared.

Question 30General Science content domains (not enumerated in source)

An object is dropped from rest near Earth's surface, and air resistance is negligible. Approximately how far does it fall in the first 2 seconds?

  1. 39.2 m
  2. 19.6 m Correct answer.
  3. 9.8 m
  4. 4.9 m

Explanation

Using d = ½gt² with g ≈ 9.8 m/s² and t = 2 s gives d = ½ × 9.8 × 4 = 19.6 m. The distance grows with the square of time because the object accelerates continuously.

Question 31General Science content domains (not enumerated in source)

Which statement best explains why the same side of the Moon always faces Earth?

  1. The Moon orbits Earth once every 24 hours
  2. The Moon's rotation period equals its orbital period around Earth Correct answer.
  3. The Moon does not rotate on its axis
  4. Earth's gravity prevents the Moon from spinning

Explanation

The Moon rotates once on its axis in the same time it takes to complete one orbit around Earth, a condition called synchronous rotation. As a result, the same lunar hemisphere stays oriented toward Earth throughout the orbit.

Question 32General Science content domains (not enumerated in source)

Which planet in the solar system has the shortest orbital period around the Sun?

  1. Earth
  2. Mars
  3. Mercury Correct answer.
  4. Venus

Explanation

Kepler's third law relates orbital period to distance from the Sun: planets closer to the Sun orbit faster. Mercury is the innermost planet, so it completes an orbit in about 88 Earth days, the shortest of any planet.

Question 33General Science content domains (not enumerated in source)

In a certain ecosystem, grasses are eaten by rabbits, and rabbits are eaten by foxes. If a disease sharply reduces the rabbit population, which change is most likely to occur first?

  1. The foxes will begin to eat grasses
  2. The fox population will decrease Correct answer.
  3. The grasses will evolve into a new species
  4. The grass population will decrease

Explanation

Foxes depend on rabbits as a food source, so a sharp decline in rabbits reduces the food available to foxes and typically causes the fox population to decline. This illustrates how a change at one trophic level propagates through a food web.

Question 34General Science content domains (not enumerated in source)

Which process in the water cycle returns water vapor from plants directly to the atmosphere?

  1. Precipitation
  2. Infiltration
  3. Transpiration Correct answer.
  4. Condensation

Explanation

Transpiration is the loss of water vapor through small openings in plant leaves, and it contributes significantly to atmospheric moisture. It is often combined with evaporation from soil as evapotranspiration.

Question 35General Science content domains (not enumerated in source)

A population of bacteria is exposed to an antibiotic, and a small number survive because they carry a gene that degrades the drug. After many generations, most of the population carries this gene. Which mechanism best explains this outcome?

  1. The bacteria mutated because they needed to survive
  2. The surviving bacteria learned to resist the drug
  3. The antibiotic caused each bacterium to develop the gene
  4. Natural selection favored bacteria with the resistance gene Correct answer.

Explanation

The resistance gene existed before exposure, and it gave carriers a survival advantage in the presence of the antibiotic. Those survivors reproduced, so the frequency of the resistance gene increased in later generations through natural selection.

Question 36General Science content domains (not enumerated in source)

Which structure in a eukaryotic cell is the primary site of aerobic ATP production?

  1. Ribosome
  2. Mitochondrion Correct answer.
  3. Golgi apparatus
  4. Lysosome

Explanation

Mitochondria house the electron transport chain and ATP synthase, which generate most of the ATP produced during aerobic cellular respiration. They are often described as the cell's powerhouses.

Question 37General Science content domains (not enumerated in source)

Which of the following is an example of a physical change rather than a chemical change?

  1. Wood burning in a fireplace
  2. Baking soda reacting with vinegar
  3. Sugar dissolving in water Correct answer.
  4. Iron rusting when exposed to moist air

Explanation

Dissolving sugar in water changes the arrangement and dispersion of sugar molecules without creating a new substance, so it is a physical change. Chemical changes produce new substances with different properties.

Question 38General Science content domains (not enumerated in source)

A 2 kg block moving at 3 m/s collides with and sticks to a stationary 1 kg block on a frictionless surface. What is the velocity of the combined blocks immediately after the collision?

  1. 1 m/s
  2. 3 m/s
  3. 2 m/s Correct answer.
  4. 1.5 m/s

Explanation

Momentum is conserved in the collision: (2 kg)(3 m/s) + (1 kg)(0) = (3 kg)(v), so v = 6/3 = 2 m/s. Because the blocks stick together, the combined mass is 3 kg.

Question 39General Science content domains (not enumerated in source)

Which statement best explains why a metal spoon left in a bowl of hot soup eventually feels hot at the handle?

  1. Hot air rises and warms the handle by convection
  2. The spoon absorbs light and converts it to heat
  3. Heat is transferred through the metal by conduction Correct answer.
  4. The metal emits thermal radiation toward the handle

Explanation

In conduction, rapidly vibrating atoms in the hot end of the metal transfer energy to neighboring atoms along the spoon. Metals conduct heat well because their delocalized electrons also carry energy efficiently.

Question 40General Science content domains (not enumerated in source)

Which statement describes a difference between a scientific hypothesis and a scientific theory?

  1. A hypothesis has been proven true, while a theory has not
  2. A hypothesis applies only to physics, while a theory applies only to biology
  3. A hypothesis is a broad explanation supported by extensive evidence, while a theory is an initial guess
  4. A hypothesis is a testable proposed explanation, while a theory is a well-supported explanation of a broad set of observations Correct answer.

Explanation

In science, a hypothesis is a testable prediction or tentative explanation for a specific observation. A theory is a well-tested, widely accepted explanation that accounts for many observations and is supported by multiple lines of evidence.

Question 41General Science content domains (not enumerated in source)

A student measures the mass of an object three times and obtains 12.1 g, 12.0 g, and 12.2 g, while the accepted value is 15.0 g. Which statement best describes the measurements?

  1. They are both accurate and precise
  2. They are neither precise nor accurate
  3. They are precise but not accurate Correct answer.
  4. They are accurate but not precise

Explanation

The three measurements cluster closely together, so they are precise. However, all of them are far from the accepted value of 15.0 g, so they are not accurate.

Question 42General Science content domains (not enumerated in source)

Which process converts atmospheric nitrogen gas into a form that plants can use?

  1. Nitrogen fixation Correct answer.
  2. Cellular respiration
  3. Transpiration
  4. Photosynthesis

Explanation

Nitrogen fixation converts inert atmospheric N₂ into ammonia or related compounds that plants can absorb. Bacteria in soil and in root nodules carry out most biological nitrogen fixation.

Question 43General Science content domains (not enumerated in source)

A 6-volt battery is connected to two 3-ohm resistors in series. What is the current through the circuit?

  1. 0.5 A
  2. 1 A Correct answer.
  3. 2 A
  4. 18 A

Explanation

In a series circuit the resistances add, giving a total of 6 ohms. Using Ohm's law, I = V/R = 6 V / 6 Ω = 1 A.

Question 44General Science content domains (not enumerated in source)

Which statement correctly compares the mass number and atomic number of an atom?

  1. The mass number counts protons and neutrons, while the atomic number counts protons Correct answer.
  2. The mass number and atomic number are always equal for every element
  3. The mass number counts protons and electrons, while the atomic number counts neutrons
  4. The mass number counts neutrons only, while the atomic number counts electrons only

Explanation

The mass number is the sum of protons and neutrons in the nucleus. The atomic number is the number of protons, which identifies the element and equals the number of electrons in a neutral atom.

Question 45General Science content domains (not enumerated in source)

Which type of electromagnetic radiation has the greatest energy per photon?

  1. Infrared radiation
  2. Ultraviolet radiation Correct answer.
  3. Radio waves
  4. Visible light

Explanation

Photon energy increases with frequency according to E = hf. Ultraviolet radiation has a higher frequency than visible light, infrared radiation, or radio waves, so its photons carry the most energy among these choices.

Question 46General Science content domains (not enumerated in source)

Which statement best explains why the Coriolis effect deflects moving air masses to the right in the Northern Hemisphere?

  1. Air pressure is always lower near the equator
  2. Ocean currents drag the atmosphere along with them
  3. The Moon's gravity pulls air masses eastward
  4. Earth rotates on its axis, so points at different latitudes move at different speeds Correct answer.

Explanation

Because Earth rotates, a point on the equator moves eastward faster than a point near the pole. Air moving across latitudes therefore appears to curve relative to the rotating surface, producing the Coriolis deflection.

Question 47General Science content domains (not enumerated in source)

A sample of an element contains atoms with the same number of protons but different numbers of neutrons. These atoms are best described as which of the following?

  1. Molecules of the element
  2. Compounds of the element
  3. Ions of the element
  4. Isotopes of the element Correct answer.

Explanation

Isotopes are atoms of the same element that have identical proton counts but different neutron counts, giving them different mass numbers. Their chemical behavior is similar because their electron configurations are the same.

Question 48General Science content domains (not enumerated in source)

Which of the following best describes the function of the cell membrane?

  1. It produces energy through photosynthesis
  2. It regulates which substances enter and leave the cell Correct answer.
  3. It stores genetic information in the form of DNA
  4. It synthesizes proteins from amino acids

Explanation

The cell membrane is a selectively permeable phospholipid bilayer that controls the movement of ions, molecules, and other substances into and out of the cell. This regulation helps maintain a stable internal environment.

Question 49General Science content domains (not enumerated in source)

A saturated solution of a sparingly soluble salt is at equilibrium with undissolved solid. If a small amount of additional solid is added and the temperature is unchanged, what happens to the concentration of dissolved ions?

  1. It increases because more solid dissolves
  2. It drops to zero because precipitation is complete
  3. It decreases because ions recombine
  4. It remains essentially unchanged because the solution is already saturated Correct answer.

Explanation

In a saturated solution the rate of dissolution equals the rate of precipitation, so the dissolved ion concentration is fixed at a given temperature. Adding more solid does not change that equilibrium concentration as long as some solid remains undissolved.

Question 50General Science content domains (not enumerated in source)

Which of the following correctly describes the relationship between wavelength, frequency, and wave speed for a wave traveling through a uniform medium?

  1. Speed equals wavelength divided by frequency
  2. Speed equals wavelength minus frequency
  3. Speed is independent of both wavelength and frequency
  4. Speed equals frequency multiplied by wavelength Correct answer.

Explanation

The wave equation states that v = fλ, so wave speed equals frequency times wavelength. In a uniform medium the speed is fixed, meaning wavelength and frequency are inversely related.