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Washington Comprehensive Assessment of Science (WCAS) Grade 8 study materials
Washington Comprehensive Assessment of Science (WCAS) Grade 8 study resources

Washington Comprehensive Assessment of Science (WCAS) Grade 8 practice questions

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Question 1Physical Science

A student pushes a box across a floor at a steady speed. Which statement best describes the forces acting on the box?

  1. The pushing force is greater than the friction force.
  2. Friction acts in the same direction as the push.
  3. The pushing force equals the friction force in size and is opposite in direction. Correct answer.
  4. No forces act on the box because it is moving steadily.

Explanation

When an object moves at constant velocity, the net force on it is zero, so opposing forces must balance. The push and friction are equal in magnitude and opposite in direction. Balanced forces do not mean no forces are present.

Question 2Physical Science

A skateboarder at rest pushes off and accelerates. Which statement explains the acceleration?

  1. The ground pushes back on the skateboarder with an unbalanced force. Correct answer.
  2. Gravity stops acting once the skateboarder moves.
  3. The skateboarder's inertia increases with speed.
  4. The skateboarder's mass decreases as they move.

Explanation

According to Newton's second law, an unbalanced net force causes acceleration. When the skater pushes the ground, the ground pushes back, producing a net force that changes the skater's motion.

Question 3Physical Science

Which quantity is a measure of how much matter an object contains, independent of where the object is located?

  1. Volume
  2. Weight
  3. Density
  4. Mass Correct answer.

Explanation

Mass measures the amount of matter and stays the same regardless of location. Weight is the gravitational force on an object and changes with gravitational field strength.

Question 4Physical Science

A moving train car collides with an identical stationary car and they lock together. If friction is negligible, what happens to the total momentum of the two-car system?

  1. It doubles because the moving car transfers all its momentum.
  2. It is conserved because no external net force acts on the system. Correct answer.
  3. It is lost as sound and heat during the collision.
  4. It becomes zero because the cars stop moving.

Explanation

In a closed system with no net external force, total momentum is conserved through a collision. Momentum may be redistributed between the cars but the total stays the same. Energy may be lost to sound and heat, but momentum is not.

Question 5Physical Science

A 4 kg cart accelerates at 3 m/s². What net force acts on the cart?

  1. 12 N Correct answer.
  2. 7 N
  3. 0.75 N
  4. 1.3 N

Explanation

Newton's second law states that net force equals mass times acceleration (F = ma). Multiplying 4 kg by 3 m/s² gives 12 N.

Question 6Physical Science

Two students push a heavy crate in the same direction with forces of 30 N and 20 N while friction resists with 40 N. What is the net force on the crate?

  1. 50 N in the direction of the pushes
  2. 90 N in the direction of the pushes
  3. 10 N opposite the pushes
  4. 10 N in the direction of the pushes Correct answer.

Explanation

Forces in the same direction add (30 N + 20 N = 50 N), and friction opposes with 40 N. Subtracting gives a net force of 10 N in the direction of the pushes.

Question 7Physical Science

A ball rolls down a smooth ramp. Which statement best describes the energy changes?

  1. Kinetic energy decreases as potential energy increases.
  2. Total mechanical energy increases because the ball speeds up.
  3. Potential energy is converted to kinetic energy as the ball descends. Correct answer.
  4. Kinetic energy stays constant while potential energy decreases.

Explanation

As the ball descends, its height decreases so gravitational potential energy decreases. That energy converts to kinetic energy, so the ball speeds up.

Question 8Physical Science

A pendulum swings from its highest point to its lowest point. At the lowest point, which statement about its energy is true?

  1. Kinetic energy equals potential energy exactly.
  2. Both kinetic and potential energy are zero.
  3. Potential energy is greatest and kinetic energy is least.
  4. Kinetic energy is greatest and potential energy is least. Correct answer.

Explanation

At the lowest point the pendulum has fallen the farthest, so gravitational potential energy is at its minimum. Its speed is greatest there, so kinetic energy is at its maximum.

Question 9Physical Science

A pot of water is heated on a stove until it boils. Which statement describes what happens to the water molecules as the water boils?

  1. The molecules lose energy and move closer together.
  2. The molecules gain enough energy to escape as a gas. Correct answer.
  3. The molecules stop moving because the water is hot.
  4. The molecules break apart into atoms of hydrogen and oxygen.

Explanation

Boiling is a phase change in which liquid molecules gain enough energy to overcome attractions and become a gas. The molecules themselves stay intact as water molecules.

Question 10Physical Science

Which statement best explains why a metal spoon in a cup of hot soup becomes warm?

  1. Cold moves from the spoon into the soup.
  2. Heat is transferred through the spoon by conduction from particle to particle. Correct answer.
  3. The spoon radiates heat back into the soup.
  4. Heat moves through the spoon by convection currents inside the metal.

Explanation

Conduction transfers thermal energy through a solid as fast-moving particles collide with slower neighbors. Metals conduct well because their particles transfer energy efficiently.

Question 11Physical Science

Two identical cups of water are placed in a room. Cup A is at 80 °C and Cup B is at 20 °C. Which statement predicts the direction of heat flow?

  1. Heat flows from Cup A to Cup B only, not to the room.
  2. Heat flows from Cup B to Cup A until both reach 50 °C.
  3. No heat flows because the cups are identical.
  4. Heat flows from Cup A to the room and Cup B until temperatures equalize. Correct answer.

Explanation

Heat flows from higher temperature to lower temperature. Cup A is hotter than the room and Cup B, so it loses energy until all reach the same temperature.

Question 12Physical Science

Which of these is an example of a wave transferring energy without transferring matter?

  1. A ball rolling across a floor
  2. A sound wave traveling through air Correct answer.
  3. A magnet pulling a paper clip
  4. A river carrying leaves downstream

Explanation

A sound wave carries energy through air as particles vibrate and pass the disturbance along, but the air itself does not travel with the wave. Mechanical motion of objects or fluids does move matter.

Question 13Physical Science

A wave has a frequency of 5 Hz and a wavelength of 2 m. What is its speed?

  1. 10 m/s Correct answer.
  2. 7 m/s
  3. 2.5 m/s
  4. 0.4 m/s

Explanation

Wave speed equals frequency multiplied by wavelength (v = f × λ). Multiplying 5 Hz by 2 m gives 10 m/s.

Question 14Physical Science

A light wave passes from air into water. Which statement describes what happens to the light?

  1. It speeds up and bends away from the normal.
  2. It slows down and bends toward the normal. Correct answer.
  3. It stops moving because water is denser.
  4. It changes into a sound wave.

Explanation

Light travels more slowly in water than in air. When a wave slows as it enters a new medium at an angle, it bends toward the normal line.

Question 15Physical Science

A student shines white light through a prism and sees a rainbow. Which statement explains this?

  1. Different colors of light bend by different amounts, separating them. Correct answer.
  2. The prism slows all colors equally so they separate.
  3. White light contains only one color that the prism splits in half.
  4. The prism adds color to the light as it passes through.

Explanation

White light is a mixture of colors, and each color refracts by a slightly different amount. This difference in bending spreads the colors into a spectrum.

Question 16Physical Science

Which statement best describes the difference between a conductor and an insulator?

  1. Both conduct charge equally well but differ in color.
  2. Conductors allow electric charge to flow easily; insulators resist charge flow. Correct answer.
  3. Insulators allow charge to flow easily; conductors block it.
  4. Conductors have no electrons; insulators have many electrons.

Explanation

Conductors contain charges that move freely, so current passes through easily. Insulators hold charges in place, resisting the flow of current.

Question 17Physical Science

A simple series circuit has a 9 V battery and a resistor of 3 Ω. What current flows through the circuit?

  1. 0.33 A
  2. 3 A Correct answer.
  3. 6 A
  4. 27 A

Explanation

Ohm's law states that current equals voltage divided by resistance (I = V/R). Dividing 9 V by 3 Ω gives 3 A.

Question 18Physical Science

In a series circuit, one light bulb burns out and all the bulbs go dark. Which statement explains this?

  1. The battery reverses its voltage when a bulb fails.
  2. The single path for current is broken, so no current flows. Correct answer.
  3. The other bulbs use up their electricity too quickly.
  4. The burned-out bulb stores all the charge in the circuit.

Explanation

A series circuit provides only one path for current. If that path is broken at any point, current cannot flow anywhere in the circuit.

Question 19Physical Science

Which arrangement of two light bulbs will keep both bulbs lit if one bulb burns out?

  1. A series circuit
  2. A parallel circuit Correct answer.
  3. A single wire connected to one bulb
  4. A circuit with no battery

Explanation

In a parallel circuit each branch has its own path to the source, so a broken branch does not stop current in the others. A series circuit shares one path, so a failure stops all current.

Question 20Physical Science

A bar magnet is brought near a pile of paper clips. Which statement best explains why the clips are attracted?

  1. The magnet creates a magnetic field that induces attraction in the clips. Correct answer.
  2. Gravity pulls the clips toward the magnet.
  3. The clips become electrically charged and attract the magnet.
  4. The magnet removes electrons from the clips.

Explanation

A magnet produces a magnetic field that can magnetize nearby magnetic materials, causing attraction. The clips are pulled by magnetic forces, not by gravity or electric charge.

Question 21Physical Science

Two bar magnets are placed with their north poles facing each other. What happens?

  1. They attract each other.
  2. They lose their magnetism permanently.
  3. They do nothing because they are identical.
  4. They repel each other. Correct answer.

Explanation

Like magnetic poles repel and opposite poles attract. Two north poles facing each other are like poles, so they push apart.

Question 22Physical Science

A student builds an electromagnet by wrapping wire around an iron nail and connecting it to a battery. Which change would strengthen the electromagnet?

  1. Disconnecting one end of the wire
  2. Replacing the battery with a piece of string
  3. Using a plastic nail instead of iron
  4. Increasing the number of wire coils around the nail Correct answer.

Explanation

The strength of an electromagnet increases with more coils of wire and greater current. More coils produce a stronger magnetic field around the core.

Question 23Physical Science

A student drops a ball from a height of 5 m. Ignoring air resistance, what happens to the ball's speed as it falls?

  1. It increases at a steady rate because gravity provides a constant acceleration. Correct answer.
  2. It increases then instantly becomes zero at the ground.
  3. It decreases because the ball loses energy.
  4. It stays constant because gravity is constant.

Explanation

Near Earth's surface gravity provides a nearly constant downward acceleration. A constant acceleration means the speed increases by the same amount each second.

Question 24Physical Science

A 2 kg block sliding at 4 m/s is brought to rest by friction. How much kinetic energy did the block have before stopping?

  1. 8 J
  2. 32 J
  3. 16 J Correct answer.
  4. 4 J

Explanation

Kinetic energy is one-half mass times speed squared (KE = ½mv²). One-half of 2 kg times (4 m/s)² equals 16 J.

Question 25Physical Science

A crate is pushed up a ramp instead of lifted straight up to the same height. Which statement best explains why the ramp makes the job easier?

  1. The ramp eliminates friction entirely.
  2. The ramp spreads the work over a longer distance, so less force is needed. Correct answer.
  3. The ramp decreases the crate's mass.
  4. The ramp reduces the total work needed to raise the crate.

Explanation

A simple machine does not reduce the total work done (ignoring friction); it trades force for distance. Pushing over a longer ramp distance requires less force to reach the same height.

Question 26Physical Science

A student measures the mass of a metal cube as 54 g and its volume as 20 cm³. What is the density of the metal?

  1. 2.7 g/cm³ Correct answer.
  2. 0.37 g/cm³
  3. 74 g/cm³
  4. 1080 g/cm³

Explanation

Density equals mass divided by volume, so divide 54 g by 20 cm³. This gives 2.7 g/cm³, a value consistent with aluminum.

Question 27Physical Science

Which statement describes a chemical change rather than a physical change?

  1. Sugar dissolving in warm water
  2. Iron forming rust when exposed to moist air Correct answer.
  3. Glass shattering into small pieces
  4. Ice melting into liquid water

Explanation

A chemical change produces a new substance with different properties. Rust is a new compound formed from iron, oxygen, and water, unlike melting, dissolving, or breaking, which leave the substance chemically the same.

Question 28Physical Science

An atom of an element has 11 protons, 12 neutrons, and 11 electrons. What is the mass number of this atom?

  1. 23 Correct answer.
  2. 12
  3. 34
  4. 11

Explanation

Mass number is the sum of protons and neutrons in the nucleus. Adding 11 protons and 12 neutrons gives 23.

Question 29Physical Science

Which statement best describes the particles in a solid?

  1. They are close together but slide past one another.
  2. They are spread out and do not interact with each other.
  3. They are closely packed and vibrate in fixed positions. Correct answer.
  4. They are far apart and move freely in all directions.

Explanation

In a solid, particles are held closely together by strong forces and can only vibrate around fixed positions. This fixed arrangement gives solids a definite shape and volume.

Question 30Physical Science

A student records the mass of a sealed container holding a small piece of burning candle before and after the candle burns completely. The container stays sealed. What should the student observe?

  1. The total mass decreases because the candle is destroyed.
  2. The total mass stays the same because matter is conserved. Correct answer.
  3. The total mass decreases because gases escape the container.
  4. The total mass increases because heat is added.

Explanation

In a closed system, atoms are rearranged during burning but none are created or lost, so total mass is conserved. Because the container is sealed, the product gases remain inside and the mass does not change.

Question 31Physical Science

Which statement best explains why a mixture of iron filings and sulfur powder can be separated with a magnet, while the compound iron sulfide cannot?

  1. In the mixture the iron has melted, but in the compound it remains solid.
  2. In the compound the iron is still magnetic, but the sulfur blocks the magnet.
  3. In the mixture the iron keeps its magnetic properties, but in the compound the elements are chemically bonded. Correct answer.
  4. In the mixture the sulfur becomes magnetic, but in the compound the sulfur loses its magnetism.

Explanation

A mixture keeps each substance's original properties, so iron filings still respond to a magnet. In a compound, elements are chemically bonded into a new substance with different properties.

Question 32Physical Science

A 5 kg object is pushed across a floor with a constant applied force of 20 N while a friction force of 8 N acts in the opposite direction. What is the acceleration of the object?

  1. 2.4 m/s² Correct answer.
  2. 5.6 m/s²
  3. 4 m/s²
  4. 1.6 m/s²

Explanation

The net force is the applied force minus friction, or 20 N − 8 N = 12 N. Using a = F/m gives 12 N ÷ 5 kg = 2.4 m/s².

Question 33Physical Science

A book rests on a table without moving. Which statement correctly describes the forces on the book?

  1. The upward normal force balances the downward gravitational force. Correct answer.
  2. The normal force is greater than the gravitational force.
  3. The gravitational force is greater than the normal force.
  4. There are no forces acting on the book because it is at rest.

Explanation

Because the book is not accelerating, the net force is zero, so the upward normal force equals the downward weight. Balanced forces produce no change in motion.

Question 34Physical Science

A skateboarder moving at 3 m/s speeds up to 9 m/s in 3 seconds. What is the skateboarder's average acceleration?

  1. 4 m/s²
  2. 2 m/s² Correct answer.
  3. 6 m/s²
  4. 3 m/s²

Explanation

Acceleration is the change in velocity divided by the time. The change is 9 m/s − 3 m/s = 6 m/s, and 6 m/s ÷ 3 s = 2 m/s².

Question 35Physical Science

A student rides a bicycle around a circular track at a constant speed of 5 m/s. Which statement about the bicycle's motion is true?

  1. Its acceleration points in the direction of motion.
  2. Its velocity is changing because its direction is changing. Correct answer.
  3. Its acceleration is zero because its speed is constant.
  4. Its velocity is constant because its speed is constant.

Explanation

Velocity is a vector that includes both speed and direction. On a circular path the direction changes continuously, so velocity changes and the bicycle accelerates toward the center.

Question 36Physical Science

A 4 kg cart moving at 3 m/s collides with and sticks to a stationary 2 kg cart. What is the speed of the combined carts after the collision?

  1. 1.5 m/s
  2. 2 m/s Correct answer.
  3. 6 m/s
  4. 3 m/s

Explanation

Momentum is conserved, so the total momentum before equals the total after. Before: 4 kg × 3 m/s = 12 kg·m/s; after: 12 kg·m/s ÷ 6 kg = 2 m/s.

Question 37Physical Science

A force of 30 N is applied to a lever at a distance of 2 m from the pivot. What torque does this force produce about the pivot?

  1. 15 N·m
  2. 32 N·m
  3. 0.067 N·m
  4. 60 N·m Correct answer.

Explanation

Torque equals force multiplied by the perpendicular distance from the pivot. Multiplying 30 N by 2 m gives 60 N·m.

Question 38Physical Science

A student lifts a 10 N box 1.5 m straight up at a constant speed. How much work does the student do on the box?

  1. 15 J Correct answer.
  2. 6.7 J
  3. 11.5 J
  4. 0 J

Explanation

Work equals force times distance when the force is in the direction of motion. Here 10 N × 1.5 m = 15 J.

Question 39Physical Science

A machine lifts a 200 N load using an input force of 50 N and has an efficiency of 80%. Which statement correctly describes the machine?

  1. The machine produces more work output than work input.
  2. The machine multiplies force with no energy loss.
  3. The machine does useful work equal to 80% of the work put into it. Correct answer.
  4. The machine has a mechanical advantage of 80.

Explanation

Efficiency compares useful work output to total work input. An 80% efficiency means 80% of the input work becomes useful output, with the rest lost mostly to friction.

Question 40Physical Science

Which statement best describes what happens to the particles of a gas when the gas is cooled in a sealed rigid container?

  1. The particles stop moving completely.
  2. The particles increase in size and take up more space.
  3. The number of particles in the container increases.
  4. The average kinetic energy of the particles decreases. Correct answer.

Explanation

Temperature is a measure of the average kinetic energy of particles. Cooling a gas lowers its average kinetic energy, so the particles move more slowly.

Question 41Physical Science

Two blocks of the same material have different masses and are heated with the same amount of energy. Which block will show the greater temperature increase?

  1. The block with the smaller mass Correct answer.
  2. The block with the larger mass
  3. Neither block will change temperature
  4. Both blocks will show the same temperature increase

Explanation

Temperature change depends on how much energy is added and how much material must be warmed. The same energy spread over less mass produces a larger temperature rise.

Question 42Physical Science

Which statement correctly describes what happens to the wavelength of a sound wave when its frequency increases, assuming the wave speed stays the same?

  1. The wavelength increases.
  2. The wavelength stays the same.
  3. The wavelength decreases. Correct answer.
  4. The wavelength becomes zero.

Explanation

Wave speed equals frequency times wavelength. If speed is constant and frequency rises, the wavelength must fall to keep the product the same.

Question 43Physical Science

A student plucks a guitar string and then plucks a thicker string of the same length and tension, which vibrates more slowly. What happens to the pitch of the sound produced?

  1. The pitch stays the same because the length is the same.
  2. The pitch is lower because the frequency is lower. Correct answer.
  3. The pitch is louder because the string is thicker.
  4. The pitch is higher because the frequency is higher.

Explanation

Pitch is determined by frequency: lower frequency produces lower pitch. A slower-vibrating string has a lower frequency, so it sounds lower.

Question 44Physical Science

A beam of light strikes a flat mirror at an angle of 30° from the normal. At what angle from the normal does the reflected beam leave the mirror?

  1. 30° Correct answer.
  2. 90°
  3. 0°
  4. 60°

Explanation

The law of reflection states that the angle of incidence equals the angle of reflection, both measured from the normal. A 30° incident angle gives a 30° reflected angle.

Question 45Physical Science

A transparent object is placed in water, and light passing into it bends away from the normal as it enters. What does this indicate about the object compared with water?

  1. The object reflects all the light that hits it.
  2. The object has the same optical density as water.
  3. Light travels slower in the object than in water.
  4. Light travels faster in the object than in water. Correct answer.

Explanation

Light bends away from the normal when it moves into a medium where it travels faster. Bending toward the normal would indicate a slower speed and higher optical density.

Question 46Physical Science

Which statement best explains why a straw appears bent where it enters a glass of water?

  1. Light from the straw changes direction as it passes from water into air. Correct answer.
  2. Light from the straw reflects off the glass and creates a shadow.
  3. Water absorbs some of the light and makes the straw look shorter.
  4. The straw actually bends when it touches the water.

Explanation

Light leaving the straw bends as it crosses the boundary between water and air because the speed of light differs in the two materials. This refraction makes the straw appear displaced at the surface.

Question 47Physical Science

A 12 V battery is connected to a circuit with two 6 Ω resistors in parallel. What is the total current drawn from the battery?

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

Explanation

For two equal resistors in parallel, the equivalent resistance is half of one resistor, or 3 Ω. Using I = V/R gives 12 V ÷ 3 Ω = 4 A.

Question 48Physical Science

A student wants to increase the strength of an electromagnet made from a coil of wire and an iron core. Which change would increase its magnetic strength?

  1. Reducing the current flowing through the coil
  2. Increasing the number of turns of wire in the coil Correct answer.
  3. Replacing the iron core with a plastic rod
  4. Spreading the coil out over a longer distance

Explanation

The magnetic field of an electromagnet grows with more turns of wire and more current. Adding turns strengthens the field produced around the iron core.

Question 49Physical Science

A charged balloon is brought near a small stream of water and the stream bends toward the balloon. Which statement best explains this?

  1. Gravity between the balloon and the water pulls the stream sideways.
  2. The balloon transfers its charge to the water, which then repels it.
  3. The water stream carries an opposite charge that attracts the balloon.
  4. The charged balloon attracts neutral water molecules by inducing a charge separation. Correct answer.

Explanation

A charged object can attract neutral matter by causing charge separation within it. The balloon pulls the opposite charges in the water closer, creating a net attraction.

Question 50Physical Science

A student measures the mass of a small rock as 24.0 grams. Which statement best describes the mass of the rock?

  1. It is a measure of the force of gravity on the rock.
  2. It is a measure of how tightly packed the rock's particles are.
  3. It is a measure of the amount of matter in the rock. Correct answer.
  4. It is a measure of the space the rock occupies.

Explanation

Mass is a fundamental property that quantifies the amount of matter in an object. Weight, volume, and density are different properties that depend on gravity, space, or particle arrangement.