Physical Science Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB) — Page 6

Question 101Question →

An isotope of an element has a mass number of $79$ and contains $45$ neutrons in its nucleus. If this neutral atom gains the minimum number of electrons required to achieve a stable octet in its outermost valence shell, what is the total number of subatomic particles (protons, neutrons, and electrons combined) in the resulting ion?

111

113

115

126

Show answer & explanation

Answer: $115$

Answer

115 total subatomic particles

The atomic number is determined by subtracting the number of neutrons from the mass number:

79 - 45 = 34

protons. An element with

34

protons has

6

valence electrons in its outer shell (configuration

2, 8, 18, 6

) and requires

2

additional electrons to form a stable octet, resulting in

36

electrons. The sum of all subatomic particles in the ion is

34\text{ protons} + 45\text{ neutrons} + 36\text{ electrons} = 115

.

Step-by-Step Solution

1

Calculate the atomic number (number of protons) of the neutral atom

Protons =

79 - 45 = 34

The mass number (

A

) equals the sum of protons (

Z

) and neutrons (

N

), so

Z = A - N

.

2

Determine the number of valence electrons and electrons needed to achieve a stable octet

Valence electrons =

6

; electrons to gain =

8 - 6 = 2

An element with atomic number

34

has an electron configuration of

2, 8, 18, 6

. It requires

2

additional electrons to fill its outer shell with

8

valence electrons.

3

Determine the total number of electrons in the resulting ion

Electrons =

34 + 2 = 36

Gaining

2

electrons to form a stable

2-

anion increases the electron count from

34

to

36

.

4

Sum all subatomic particles (protons, neutrons, and electrons)

Total particles =

34 + 45 + 36 = 115

The total particle count is the sum of protons (

34

), neutrons (

45

), and electrons (

36

).

Key Concept

Calculating subatomic particle totals using mass number, neutron count, valence electron configurations, and ion formation.

Estimated Time:1m 30s

Question 102Question →

When an iron nail is exposed to moist air over several weeks, it reacts with oxygen gas to form iron(III) oxide (rust), as represented by the balanced equation $4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3$ . Which of the following statements correctly explains why this process is classified as a chemical change?

The iron metal merely undergoes a state change from solid to liquid due to environmental humidity.

The iron nail dissolves reversibly in atmospheric water vapor without forming any new chemical bonds.

New chemical bonds are formed between iron and oxygen atoms, producing a substance with different chemical properties.

The chemical formula subscripts of the elemental reactants change during the reaction to force the equation to balance.

Show answer & explanation

Answer: New chemical bonds are formed between iron and oxygen atoms, producing a substance with different chemical properties.

Answer

New chemical bonds are formed between iron and oxygen atoms, producing a substance with different chemical properties.

The reaction produces iron(III) oxide (

\text{Fe}_2\text{O}_3

), which is a distinct compound with chemical and physical properties entirely different from elemental iron and gaseous oxygen. Because chemical bonds are broken and new bonds are formed, the process is a chemical change.

Step-by-Step Solution

1

Analyze the reactants and products in the reaction

4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3

.

Elemental iron (

\text{Fe}

) and oxygen gas (

\text{O}_2

) react to produce the compound iron(III) oxide (

\text{Fe}_2\text{O}_3

).

Determining the chemical formulas reveals whether original substances underwent composition changes.

2

Distinguish between a physical change and a chemical change.

Physical changes alter appearance or physical state without changing chemical identity, whereas chemical changes form new chemical bonds and new substances.

Rust possesses distinct chemical reactivity, color, and magnetic properties compared to metallic iron and oxygen gas.

3

Identify the statement matching the definition of a chemical change.

The formation of new bonds producing a compound with distinct properties defines the reaction as a chemical change.

This directly demonstrates the fundamental principle of chemical reactions.

Key Concept

Chemical change versus physical change and compound formation

Estimated Time:1m 0s

Question 103Question →

When one end of an iron rod is placed directly into a campfire, the opposite end eventually becomes too hot to hold safely. Through which process is heat energy primarily transferred along the length of the solid metal rod?

Convection

Conduction

Radiation

Evaporation

Show answer & explanation

Answer: Conduction

Answer

Conduction

Conduction is the process by which thermal energy is transferred through stationary matter by microscopic particle collisions and free electron movement. In metals, this occurs rapidly because mobile electrons efficiently transfer kinetic energy from the heated end to the cooler end.

Step-by-Step Solution

1

Identify the physical medium and mode of energy movement

Thermal energy travels through a solid, stationary metal rod from the hotter end to the cooler end.

In solids, atoms are fixed in place, meaning energy must be passed along via vibrations and collisions rather than bulk fluid circulation.

2

Match the observed physical process with the correct heat transfer classification

Direct transfer of thermal kinetic energy between adjacent atoms and free electrons is defined as conduction.

Conduction specifically governs heat propagation through direct particle-to-particle interaction in solids.

Key Concept

Thermal conduction in solid materials

Estimated Time:40s

Question 104Question →

A cook dissolves table salt into a pot of warm water until the crystals are no longer visible. When the water is later boiled away completely, solid salt crystals remain at the bottom of the pot. Which of the following best classifies the dissolving of the salt?

A chemical change, because the solid crystals initially disappeared from view.

A decrease in total mass, because the dissolved salt no longer occupies physical space.

A physical change, because the chemical identity of the salt was preserved.

A chemical change, because thermal energy was required to separate the salt from the water.

Show answer & explanation

Answer: A physical change, because the chemical identity of the salt was preserved.

Answer

Dissolving salt in water is a physical change because the chemical identity of the substance does not change and the process is reversible.

A physical change occurs when the form, phase, or appearance of a substance changes without altering its chemical identity. Because salt can be completely recovered in its original form simply by evaporating the water, no chemical reaction took place.

Step-by-Step Solution

1

Analyze whether new substances were formed during the dissolving process.

The salt (

NaCl

) disperses into sodium and chloride ions in water, but its chemical identity remains unchanged.

Chemical changes require the formation of entirely new substances with distinct chemical formulas.

2

Evaluate the reversibility of the separation.

Evaporating or boiling off the water leaves the original salt crystals intact.

Physical mixtures can be separated by physical means such as evaporation, confirming a physical change.

Key Concept

Physical changes alter the form or state of matter without changing its chemical composition, allowing original substances to be recovered by physical methods.

Estimated Time:45s

Question 105Question →

In mechanical systems, energy exists in various forms and can be transferred or transformed to accomplish tasks. Match each mechanical scenario with the primary physical concept it illustrates.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Compressed suspension spring matches Elastic potential energy stored due to mechanical deformation; Rotating flywheel matches Kinetic energy stored within the motion of a mass; Electric winch delivering energy per second matches Mechanical power representing the rate at which work is performed; Hydraulic cylinder sliding a container matches Mechanical work accomplished by applying a force over a displacement.

Each scenario directly exemplifies a fundamental physical definition in mechanics: holding a compressed spring stores elastic potential energy, a spinning flywheel stores rotational kinetic energy, rating an output by energy transferred per second defines power, and exerting a force across a distance performs work.

Step-by-Step Solution

1

Identify the state of energy in the compressed coil spring.

The spring is stationary but held under compression, meaning potential energy is stored in its elastic structure.

Elastic potential energy is stored when an object is temporarily deformed by a force.

2

Determine the physical quantity represented by the rotating flywheel.

The flywheel possesses energy by virtue of its continuous physical motion.

Any moving mass possesses kinetic energy, whether in linear or rotational motion.

3

Analyze the action of the electric winch delivering energy per unit time.

Energy delivered per second defines the rate of doing work, which is power.

Power is defined as work done divided by time (

P = \frac{W}{t}

).

4

Evaluate the hydraulic cylinder moving a crate with a force across a distance.

A force acting over a displacement performs mechanical work (

W = F \cdot d

).

Work is the transfer of energy that occurs when an applied force causes a displacement.

Key Concept

Work, Energy, and Power Definitions and Transformations

Estimated Time:1m 15s

Question 106Question →

Wave interactions with boundaries, media, and observers produce distinct observable phenomena. Match each wave phenomenon on the left with its corresponding physical scenario on the right.

Click a left item, then click its matching right item

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Answer

Refraction correctly matches the submerged pencil appearing broken at the water boundary; Diffraction correctly matches hearing sound around a hallway corner; Doppler Effect correctly matches the siren pitch increasing during vehicle approach; Total Internal Reflection correctly matches light signal confinement in optical fibers.

Each wave phenomenon matches its exact governing physical principle: Refraction is the bending of light due to speed variation across media; Diffraction is wave spreading around physical obstacles; Doppler Effect is the frequency shift due to relative source motion; Total Internal Reflection is complete optical confinement based on critical angle reflection.

Step-by-Step Solution

1

Analyze the phenomenon of wave speed changes across differing media boundaries.

Refraction occurs when light enters water from air, decelerating and changing path, which visually displaces the submerged portion of a pencil.

Different medium densities alter the phase velocity of light, bending the transmitted ray.

2

Analyze how waves navigate physical edges and barrier corners.

Diffraction enables acoustic wavefronts to bend around hallway corners without requiring medium changes or reflection.

Audible sound wavelengths are large enough relative to corner dimensions to produce substantial diffraction.

3

Analyze the impact of relative source-observer velocity on wave frequency.

The Doppler Effect causes wavefront compression ahead of an approaching siren, increasing observed frequency and pitch.

Relative motion changes the rate at which wave crests reach the observer.

4

Analyze the optical boundary condition where refraction ceases and complete internal reflection occurs.

Total Internal Reflection retains light pulses entirely inside higher-index fiber glass cores when incident angles exceed the critical angle.

Transmission into lower-index cladding is prevented when the critical angle is exceeded.

Key Concept

Wave interactions and principles: Refraction, Diffraction, Doppler Shift, and Total Internal Reflection

Estimated Time:1m 30s

Question 107Question →

Arrange the following physical states and temperatures of water in order of increasing average molecular kinetic energy, from the lowest thermal energy state to the highest thermal energy state.

Drag items to arrange them in the correct order

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Answer

The correct sequence from lowest to highest molecular kinetic energy is: Ice at

-10^\circ\text{C}

, followed by Liquid water at

20^\circ\text{C}

, then Liquid water at

100^\circ\text{C}

, and finally Superheated steam at

120^\circ\text{C}

.

Temperature is directly proportional to the average kinetic energy of the molecules in a substance. In the solid phase (ice at

-10^\circ\text{C}

), molecules vibrate minimally within a lattice. As thermal energy is added, ice melts into liquid water, where molecules move with greater kinetic energy at

20^\circ\text{C}

and even faster at

100^\circ\text{C}

. When vaporized into steam and heated to

120^\circ\text{C}

, the gaseous molecules move freely at the highest average speeds, having the highest molecular kinetic energy.

Step-by-Step Solution

1

Relate temperature and phase state to molecular kinetic energy.

Temperature measures the average kinetic energy of constituent particles, while phase changes (solid to liquid to gas) require thermal energy input.

Particles in solids vibrate in place, liquids exhibit fluid molecular translation, and gases feature rapid, independent molecular motion.

2

Rank the solid and lower-temperature liquid states.

Ice at

-10^\circ\text{C}

has less kinetic energy than liquid water at

20^\circ\text{C}

.

Sub-zero solid ice possesses lower temperature and rigid intermolecular structure compared to liquid at room temperature.

3

Rank the higher-temperature liquid and gaseous states.

Liquid water at

100^\circ\text{C}

is higher in kinetic energy than water at

20^\circ\text{C}

, but lower than steam at

120^\circ\text{C}

.

Molecules in gaseous steam at

120^\circ\text{C}

move far more rapidly and independently than molecules in boiling liquid water.

Key Concept

Temperature as a measure of average molecular kinetic energy across solid, liquid, and gas phases

Estimated Time:45s

Question 108Question →

Matter undergoes different physical transitions as thermal energy is added or removed. Match each phase change term on the left with its correct physical description on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Sublimation matches 'The transition of a substance directly from a solid into a gas'; Condensation matches 'The transition of a substance from a gas into a liquid'; Freezing matches 'The transition of a substance from a liquid into a solid'; Melting matches 'The transition of a substance from a solid into a liquid'.

Each phase transition is correctly matched based on the initial and final physical states of matter: Sublimation represents solid to gas directly, Condensation represents gas to liquid, Freezing represents liquid to solid, and Melting represents solid to liquid.

Step-by-Step Solution

1

Identify the initial and final states of matter for each term.

Each phase change corresponds to a specific pair of initial and final physical states.

Phase changes are classified by the movement of particles between solid, liquid, and gas phases.

2

Connect Sublimation to its direct phase shift.

Sublimation pairs with the direct shift from solid to gas.

Sublimation skips the liquid state entirely, as seen with dry ice.

3

Connect Condensation to its phase shift.

Condensation pairs with the change from gas to liquid.

Water vapor turning into liquid droplets on a cold surface is the classic example of condensation.

4

Connect Freezing and Melting to their respective liquid-solid boundaries.

Freezing pairs with liquid to solid, while Melting pairs with solid to liquid.

Melting adds heat to liquefy a solid, whereas freezing removes heat to solidify a liquid.

Key Concept

Phase Changes of Matter

Estimated Time:45s

Question 109Question →

A mechanical crane lifts a cargo container with a mass of $500\text{ kg}$ vertically upward. If the crane's cable exerts a constant upward tension of $6{}400\text{ N}$ and the acceleration due to gravity is $9.8\text{ m/s}^2$ , what is the upward acceleration of the container?

12.8\text{ m/s}^2

3\text{ m/s}^2

11.8\text{ m/s}^2

0.3\text{ m/s}^2

Show answer & explanation

Answer: $3\text{ m/s}^2$

Answer

3\text{ m/s}^2

The container experiences two vertical forces: an upward tension of

6{}400\text{ N}

and a downward gravitational force (weight) of

W = mg = 500\text{ kg} \times 9.8\text{ m/s}^2 = 4{}900\text{ N}

. The net upward force is

6{}400\text{ N} - 4{}900\text{ N} = 1{}500\text{ N}

. Applying Newton's second law (

a = F_{\text{net}} / m

) gives an acceleration of

1{}500\text{ N} / 500\text{ kg} = 3\text{ m/s}^2

.

Step-by-Step Solution

1

Calculate the downward gravitational force (weight) acting on the container.

W = mg = 500\text{ kg} \times 9.8\text{ m/s}^2 = 4{}900\text{ N}

Weight is the force exerted on the mass by gravity.

2

Find the net upward force by subtracting weight from the upward cable tension.

F_{\text{net}} = F_{\text{tension}} - W = 6{}400\text{ N} - 4{}900\text{ N} = 1{}500\text{ N}

The acceleration depends on the resultant unbalanced force acting on the object.

3

Apply Newton's second law (

a = F_{\text{net}} / m

) to determine the acceleration.

a = \frac{1{}500\text{ N}}{500\text{ kg}} = 3\text{ m/s}^2

Acceleration equals net force divided by total mass.

Key Concept

Newton's Second Law and Net Vertical Force

Estimated Time:1m 0s

Question 110Question →

An atom of an unknown element forms a stable ion with a $+3$ charge. This specific ion contains $10$ electrons. If the mass number of a particular isotope of this element is equal to twice its atomic number plus one, how many neutrons does the nucleus of this isotope contain?

8

11

14

27

Show answer & explanation

Answer: 14

Answer

The isotope contains 14 neutrons.

To solve this, first find the atomic number. A

+3

ion has lost 3 electrons. Since this ion has 10 electrons, the neutral atom must have

10 + 3 = 13

protons (atomic number 13). Next, calculate the mass number using the provided formula:

2(13) + 1 = 27

. Finally, subtract the number of protons from the mass number to find the number of neutrons:

27 - 13 = 14

.

Step-by-Step Solution

1

Determine the atomic number (number of protons).

The atomic number is 13.

A

+3

charge indicates the neutral atom lost 3 negatively charged electrons. Since the ion has 10 electrons, the neutral atom originally had

10 + 3 = 13

electrons. The number of protons equals the number of electrons in a neutral atom.

2

Calculate the mass number.

The mass number is 27.

The problem states the mass number is twice the atomic number plus one:

2(13) + 1 = 27

.

3

Calculate the number of neutrons.

There are 14 neutrons.

The number of neutrons is found by subtracting the atomic number (protons) from the mass number:

27 - 13 = 14

.

Key Concept

Calculating subatomic particles for ions by first determining the true atomic number from the ion's charge and electron count, then utilizing mass number relationships.

Estimated Time:1m 30s

Question 111Question →

During the summer, the upper floors and attic of a multi-story house are typically noticeably warmer than the ground floor. Which heat transfer process is primarily responsible for the circulation that causes warm air to rise toward the ceiling and upper floors?

Conduction

Convection

Radiation

Condensation

Show answer & explanation

Answer: Convection

Answer

Convection is the primary heat transfer process responsible for warm air rising to the upper floors.

Convection is the transfer of heat by the actual physical movement of heated fluid particles in liquids and gases. When air is heated, it expands, becomes less dense than the cooler air around it, and rises toward the upper levels of the structure.

Step-by-Step Solution

1

Identify the state of matter and thermal mechanism in the scenario.

Air is a fluid gas that expands upon warming, decreases in density, and moves upward.

Thermal expansion reduces the density of heated air, creating upward buoyancy forces.

2

Classify this fluid motion under the appropriate heat transfer category.

The macroscopic movement of a warm fluid transporting heat upward is defined as convection.

Convection specifically accounts for thermal transport resulting from bulk fluid circulation.

Key Concept

Thermal convection in fluids

Estimated Time:45s

Question 112Question →

When solid zinc metal is immersed in hydrochloric acid, a single displacement reaction occurs that produces aqueous zinc chloride and hydrogen gas. Based on the law of conservation of mass, what stoichiometric coefficient and chemical formula correctly complete the balanced chemical equation below?

Fill in the blanks below

$\text{Zn} + \text{HCl} \rightarrow \text{ZnCl}_2 + $

Show answer & explanation

Answer

The balanced chemical equation is completed by placing a coefficient of 2 in front of HCl and identifying H₂ (hydrogen gas) as the missing diatomic product.

In a single replacement reaction between zinc and hydrochloric acid, zinc displaces hydrogen to form zinc chloride (

\text{ZnCl}_2

) and diatomic hydrogen gas (

\text{H}_2

). To balance the

2

chlorine atoms and

2

hydrogen atoms present in the products, a coefficient of

2

must precede

\text{HCl}

on the reactant side.

Step-by-Step Solution

1

Determine the identity of the missing product from the chemical reaction description

The reaction produces zinc chloride (

\text{ZnCl}_2

) and diatomic hydrogen gas (

\text{H}_2

).

When a reactive metal displaces hydrogen from an acid in a single replacement reaction, hydrogen is liberated as diatomic gas molecules.

2

Count the number of each type of atom on the product side

Products contain

1

zinc (

\text{Zn}

) atom,

2

chlorine (

\text{Cl}

) atoms, and

2

hydrogen (

\text{H}

) atoms.

According to the law of conservation of mass, matter cannot be created or destroyed, so the reactant side must contain identical atom counts.

3

Balance the reactant side by determining the required coefficient for hydrochloric acid

Placing a coefficient of

2

before

\text{HCl}

yields

2

hydrogen atoms and

2

chlorine atoms.

One formula unit of

\text{Zn}

supplies

1

zinc atom, and

2

formula units of

\text{HCl}

supply the required

2

hydrogen and

2

chlorine atoms.

Key Concept

Single displacement reactions and balancing equations using the law of conservation of mass

Estimated Time:1m 0s

Question 113Question →

In the study of classical mechanics, various terms describe the motion of bodies and the forces acting upon them. Match each mechanics concept on the left with its correct physical definition on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Momentum corresponds to the product of mass and velocity; Acceleration corresponds to the rate of change of velocity; Inertia corresponds to the resistance to change in motion; Weight corresponds to the gravitational force acting on an object's mass.

Each mechanics term addresses a specific physical property or relationship: Momentum measures the quantity of motion (

p = mv

), Acceleration measures how fast velocity changes (

a = \frac{\Delta v}{\Delta t}

), Inertia is the inherent resistance to changes in motion, and Weight is the gravitational force acting on mass (

W = mg

).

Step-by-Step Solution

1

Identify the definition of Momentum

Momentum is mathematically defined as mass multiplied by velocity (

p = mv

), which matches the statement regarding the quantity of motion.

Momentum quantifies the kinetic impact and difficulty of stopping a moving object.

2

Identify the definition of Acceleration

Acceleration is the derivative or rate of change of velocity over time (

a = \frac{\Delta v}{\Delta t}

), matching the definition involving changes in speed or direction.

Any vector change in velocity over time constitutes acceleration.

3

Identify the definition of Inertia

Inertia corresponds to Newton's first law concept—the inherent tendency of matter to resist alterations to its motion or rest.

Inertia is a property of mass rather than a force or rate.

4

Identify the definition of Weight

Weight is the gravitational force exerted on a mass (

W = mg

), matching the downward planetary force definition.

Unlike invariant mass, weight is a force that changes based on local gravity.

Key Concept

Distinguishing core classical mechanics concepts: momentum, acceleration, inertia, and weight.

Estimated Time:1m 0s

Question 114Question →

Match each thermal physics concept with its correct scientific definition.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Specific heat capacity pairs with the amount of heat energy required to raise the temperature of a unit mass by one degree Celsius; Thermal equilibrium pairs with the state where two objects reach the same temperature and net heat transfer ceases; Thermal expansion pairs with the increase in volume or length of a substance resulting from an increase in temperature.

Each thermal property accurately aligns with its fundamental physical definition: specific heat capacity quantifies thermal energy required for temperature change per unit mass, thermal equilibrium defines the zero net heat transfer condition at equal temperatures, and thermal expansion describes dimensional growth due to increased kinetic vibration of particles.

Step-by-Step Solution

1

Identify the definition for specific heat capacity

Matches the definition involving the energy required per unit mass to produce a temperature change of one degree Celsius.

Specific heat capacity is quantitatively defined as

c = \frac{Q}{m\Delta T}

.

2

Identify the definition for thermal equilibrium

Matches the condition where temperatures equalize and net heat flow between systems stops.

By the zeroth law of thermodynamics, thermal equilibrium describes balanced temperatures with zero net thermal transfer.

3

Identify the definition for thermal expansion

Matches the physical enlargement (length or volume increase) of matter due to rising temperature.

Higher temperature increases molecular kinetic energy, causing atoms or molecules to separate slightly and expand the material.

Key Concept

Thermodynamic definitions and thermal properties of matter

Estimated Time:45s

Question 115Question →

An automotive technician pours a sample of hydraulic fluid with a density of $0.85\text{ g/cm}^3$ into a graduated container. If the fluid sample occupies a volume of $200\text{ cm}^3$ , what is the mass of the fluid in grams?

Show answer & explanation

Answer: 170

Answer

The mass of the hydraulic fluid sample is

170\text{ g}

.

Density is defined as the amount of mass contained within a given unit volume (

\text{Density} = \frac{\text{Mass}}{\text{Volume}}

). Rearranging this formula to solve for mass gives

\text{Mass} = \text{Density} \times \text{Volume}

. Multiplying the fluid's density of

0.85\text{ g/cm}^3

by its volume of

200\text{ cm}^3

yields a total mass of

170\text{ g}

.

Step-by-Step Solution

1

State the formula relating mass, density, and volume:

\text{Mass} = \text{Density} \times \text{Volume}

.

\text{Mass} = 0.85\text{ g/cm}^3 \times 200\text{ cm}^3

Density represents mass per unit volume (

\text{Density} = \frac{\text{Mass}}{\text{Volume}}

), so rearranging to solve for mass requires multiplying density by volume.

2

Multiply the numerical values to compute the total mass.

\text{Mass} = 170\text{ g}

0.85 \times 200 = 170

.

Key Concept

Calculating mass from density and volume (

m = \rho \times V

)

Estimated Time:45s

Question 116Question →

Electromagnetic radiation spans a continuous spectrum of wavelengths and frequencies, with all waves traveling at the speed of light in a vacuum. What is the correct sequence of the following electromagnetic radiation bands when arranged in order from lowest frequency to highest frequency?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct order from lowest frequency to highest frequency is Microwave radiation, followed by Infrared radiation, then Ultraviolet radiation, and finally Gamma radiation.

Electromagnetic waves propagate at

c \approx 3 \times 10^8\text{ m/s}

in a vacuum according to the relationship

c = f\lambda

. As wavelength decreases, wave frequency and photon energy (

E = hf

) increase. Arranging the given bands from lowest frequency to highest frequency yields Microwave radiation (

10^{9}\text{ to }10^{11}\text{ Hz}

), Infrared radiation (

10^{12}\text{ to }4 \times 10^{14}\text{ Hz}

), Ultraviolet radiation (

8 \times 10^{14}\text{ to }3 \times 10^{16}\text{ Hz}

), and Gamma radiation (

> 10^{19}\text{ Hz}

).

Step-by-Step Solution

1

Recall the inverse relationship between wavelength and frequency in electromagnetic waves.

All electromagnetic waves travel at the speed of light in vacuum (

c = f\lambda

), meaning that frequency (

f

) increases as wavelength (

\lambda

) decreases.

Determining the correct frequency sequence requires ordering the wave bands from longest wavelength to shortest wavelength.

2

Identify the band with the longest wavelength and lowest frequency.

Microwaves exhibit wavelengths between

1\text{ mm}

and

1\text{ m}

(

f \approx 10^{9}\text{ to }10^{11}\text{ Hz}

), making it the first item in the sequence.

Microwaves sit just above radio waves at the low-frequency end of the spectrum.

3

Order the intermediate bands relative to visible light.

Infrared lies below visible red light (

f \approx 10^{12}\text{ to }4 \times 10^{14}\text{ Hz}

), and ultraviolet lies above visible violet light (

f \approx 8 \times 10^{14}\text{ to }3 \times 10^{16}\text{ Hz}

).

Infrared has a lower frequency than ultraviolet because its photon energy is lower.

4

Identify the band with the shortest wavelength and highest frequency.

Gamma rays possess extremely short wavelengths (

< 10\text{ pm}

) and the highest frequencies (

> 10^{19}\text{ Hz}

).

Gamma rays sit at the highest-energy boundary of the electromagnetic spectrum.

Key Concept

Electromagnetic Spectrum Frequency and Wavelength Relationships

Estimated Time:1m 15s

Question 117Question →

A stunt car with a mass of $800\text{ kg}$ accelerates from rest to a speed of $20\text{ m/s}$ along a straight, level track. How much work is done by the net force to accelerate the car?

8{}000\text{ J}

16{}000\text{ J}

160{}000\text{ J}

320{}000\text{ J}

Show answer & explanation

Answer: $160{}000\text{ J}$

Answer

160{}000\text{ J}

According to the work-energy theorem, the net work performed on an object equals its change in kinetic energy (

W = \Delta KE

). Because the car accelerates from rest, its initial kinetic energy is zero. The final kinetic energy is calculated as

\frac{1}{2}mv^2 = \frac{1}{2}(800\text{ kg})(20\text{ m/s})^2 = 400 \times 400 = 160{}000\text{ J}

. Thus, the work done on the car is

160{}000\text{ J}

.

Step-by-Step Solution

1

Apply the work-energy theorem to relate the net work done to the change in kinetic energy.

W = \Delta KE = KE_{\text{final}} - KE_{\text{initial}}

The net work done on an object equals the change in its kinetic energy.

2

Calculate the initial and final kinetic energy values.

KE_{\text{initial}} = 0\text{ J}

and

KE_{\text{final}} = \frac{1}{2}mv^2 = \frac{1}{2}(800\text{ kg})(20\text{ m/s})^2 = 400 \times 400 = 160{}000\text{ J}

The car starts from rest (

v_0 = 0\text{ m/s}

) and reaches a speed of

20\text{ m/s}

.

3

Determine the net work done on the car.

W = 160{}000\text{ J} - 0\text{ J} = 160{}000\text{ J}

Subtracting initial kinetic energy from final kinetic energy yields total work.

Key Concept

Work-Energy Theorem and Kinetic Energy Calculation

Estimated Time:1m 0s

Question 118Question →

A neutral atom of fluorine has an atomic number of $9$ and a mass number of $19$ . How many neutrons are contained in the nucleus of this atom?

9

10

19

28

Show answer & explanation

Answer: $10$

Answer

The nucleus contains

10

neutrons.

The mass number (

A = 19

) is the total number of protons and neutrons in the nucleus. The atomic number (

Z = 9

) represents the number of protons. The number of neutrons is determined by subtracting the atomic number from the mass number:

19 - 9 = 10

.

Step-by-Step Solution

1

Identify the given atomic number and mass number.

Atomic number (

Z

) =

9

, Mass number (

A

) =

19

.

The atomic number indicates the number of protons, while the mass number represents the sum of protons and neutrons.

2

Apply the subatomic particle calculation formula:

\text{Number of Neutrons} = \text{Mass Number} (A) - \text{Atomic Number} (Z)

.

19 - 9 = 10

Subtracting the number of protons from the total nucleon count yields the number of neutrons.

Key Concept

Subatomic particle calculation using atomic number and mass number

Estimated Time:45s

Question 119Question →

Chemical reactions can be grouped into distinct categories based on how atoms and ions are rearranged. Match each chemical reaction equation on the left with its correct classification type on the right. Which reaction type correctly pairs with each equation?

Click a left item, then click its matching right item

Show answer & explanation

Answer

The magnesium burning equation pairs with synthesis, hydrogen peroxide breakdown pairs with decomposition, copper reacting with silver nitrate pairs with single displacement, and silver nitrate reacting with sodium chloride pairs with double displacement.

Each chemical reaction matches its structural pattern: synthesis creates one product from multiple reactants, decomposition breaks one reactant into multiple products, single displacement involves a free element displacing an ion from a compound, and double displacement involves two ionic compounds exchanging ion partners.

Step-by-Step Solution

1

Analyze the number and structure of reactants and products for the first equation (

2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}

).

Two elemental reactants combine into one compound (

A + B \rightarrow AB

).

This matches the definition of a synthesis (or combination) reaction.

2

Analyze the second equation (

2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2

).

A single compound reactant yields two distinct product molecules (

AB \rightarrow A + B

).

This matches the definition of a decomposition reaction.

3

Analyze the third equation (

\text{Cu} + 2\text{AgNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{Ag}

).

An uncombined element replaces an ion in a compound (

A + BC \rightarrow AC + B

).

This is characteristic of a single replacement/displacement reaction.

4

Analyze the fourth equation (

\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl} + \text{NaNO}_3

).

Two ionic compounds swap binding partners (

AB + CD \rightarrow AD + CB

).

This is the hallmark of a double replacement/displacement reaction.

Key Concept

Classification of Major Chemical Reaction Types

Estimated Time:1m 0s

Question 120Question →

Arrange the following examples of electromagnetic radiation in order of DECREASING wavelength, from the longest wavelength (first) to the shortest wavelength (last).

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct order from longest to shortest wavelength is: AM radio broadcasts (Radio), air traffic control radar (Microwave), thermal imaging (Infrared), sunburn-causing radiation (Ultraviolet), and PET scan emissions (Gamma rays).

The correct sequence maps each application to its electromagnetic band and orders them strictly by decreasing wavelength. Radio waves (AM radio) have the longest wavelengths, followed by microwaves (radar), infrared (thermal imaging), ultraviolet (sunburns), and finally gamma rays (PET scans) with the shortest wavelengths.

Step-by-Step Solution

1

Identify the electromagnetic spectrum band corresponding to each real-world application.

AM radio = Radio waves; Radar = Microwaves; Thermal imaging = Infrared; Sunburn = Ultraviolet; PET scan = Gamma rays.

Mapping the practical examples to their scientific classification is necessary to compare their physical properties.

2

Recall the standard order of the electromagnetic spectrum bands.

The bands in sequence are: Radio, Microwave, Infrared, Visible light, Ultraviolet, X-ray, Gamma ray.

The spectrum is a continuous sequence organized by the fundamental properties of the waves.

3

Determine the direction of decreasing wavelength across the spectrum.

Wavelength is longest for Radio waves and continuously decreases towards Gamma rays, which have the shortest wavelength.

Wavelength and frequency are inversely proportional. Since energy and frequency increase from Radio to Gamma, wavelength must decrease in that same direction.

4

Arrange the identified applications from longest wavelength to shortest wavelength.

Radio (longest), then Microwave, Infrared, Ultraviolet, and Gamma rays (shortest).

This sequence perfectly matches the decreasing wavelength criteria requested in the stem.

Key Concept

Electromagnetic Spectrum and Wavelength Properties

Physical Science

Answer

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