Unit Checkpoint
Unit Review
Congratulations on reaching the final lesson of the Waves, Light and Sound unit! This checkpoint will test your understanding of all the concepts covered in this unit. Review the key topics below before attempting the assessment.
Key Concepts from This Unit
Wave Basics (Lesson 1)
- Waves transfer energy without transferring matter
- Amplitude: height of wave from rest to peak
- Wavelength: distance from one point to the same point on the next wave
- Frequency: number of waves passing a point per second
Light and Sound (Lesson 2)
- Light is an electromagnetic wave; sound is a mechanical wave
- Light can travel through a vacuum; sound cannot
- Light travels much faster than sound (about 880,000 times faster in air)
- Amplitude affects loudness (sound) and brightness (light)
- Frequency affects pitch (sound) and color (light)
Guided Practice (Lesson 3)
- Applied wave concepts through practice problems
- Connected wave properties to real-world observations
Primary Source Analysis (Lesson 4)
- Interpreting scientific data tables
- Finding patterns in experimental results
- Sound speed varies by material: solids fastest, gases slowest
Claim-Evidence-Reasoning (Lesson 5)
- Claim: answers a question with a specific statement
- Evidence: data and observations that support the claim
- Reasoning: explains WHY the evidence supports the claim using science
Assessment Instructions
This checkpoint contains 10 questions covering all lessons in the unit. These questions require you to apply your knowledge, not just recall facts. Take your time and think carefully about each question.
Tips for Success
- Read each question completely before answering
- Look for key terms that connect to concepts you learned
- When asked to explain, use the CER framework
- Check that your answer makes sense scientifically
- If stuck, think about what you know and work from there
Unit Checkpoint Assessment
Answer all 10 questions. Click each question to reveal the answer after you have attempted it.
Question 1: A guitar string vibrates 440 times per second. What is the frequency of this wave, and what property of sound does frequency determine?
Answer: The frequency is 440 Hz (hertz). Frequency determines the pitch of a sound. A frequency of 440 Hz is the musical note A above middle C. Higher frequencies produce higher-pitched sounds; lower frequencies produce lower-pitched sounds.
Question 2: Explain why we see lightning before we hear thunder, even when they happen at the same time. Use specific numbers if possible.
Answer: Light travels at about 300,000 kilometers per second, while sound travels at only about 343 meters per second in air. Light is nearly 880,000 times faster than sound. When lightning strikes, both the flash (light) and thunder (sound) are produced simultaneously, but the light reaches our eyes almost instantly while the sound takes time to travel. For every 5 seconds between seeing lightning and hearing thunder, the storm is about 1 mile away.
Question 3: A student claims that sound travels faster through air than through water because air is easier to move through. Use the CER framework to respond to this claim.
Answer:
Claim: The student's claim is incorrect. Sound actually travels faster through water than through air.
Evidence: Experimental data shows sound travels at 343 m/s in air but 1,480 m/s in water - more than 4 times faster.
Reasoning: Sound is a vibration that passes from particle to particle. In water, molecules are closer together than in air, so vibrations transfer more quickly between them. The "ease of movement" the student mentions actually slows sound down because particles must travel farther to bump into the next particle.
Question 4: What is the difference between amplitude and wavelength? Draw or describe what each measures on a wave.
Answer: Amplitude measures the height of a wave - specifically, the distance from the resting position (middle line) to the highest point (crest) or lowest point (trough). It represents the energy in the wave. Wavelength measures the length of one complete wave cycle - the horizontal distance from one crest to the next crest, or from any point to the same point on the next wave. Amplitude is a vertical measurement; wavelength is a horizontal measurement.
Question 5: Use the following data to answer: Sound travels at 343 m/s in air, 1,480 m/s in water, and 5,960 m/s in steel. If you were 1 kilometer away from a sound source, how much sooner would the sound reach you through a steel rail compared to through air? (Round to the nearest second)
Answer:
Time through air: 1000m / 343 m/s = 2.92 seconds
Time through steel: 1000m / 5960 m/s = 0.17 seconds
Difference: 2.92 - 0.17 = 2.75 seconds, which rounds to about 3 seconds sooner through the steel rail.
This is why people put their ear to railroad tracks to hear if a train is coming - the sound through the steel arrives much sooner than through the air.
Question 6: Why can astronauts see each other in space but cannot hear each other without radios?
Answer: Light and sound are different types of waves. Light is an electromagnetic wave that does not need a medium to travel - it can pass through the vacuum of space. Sound is a mechanical wave that requires a medium (solid, liquid, or gas) to travel through because it works by vibrating particles. Space is a vacuum with no particles, so sound waves cannot travel through it. Radios work by converting sound to radio waves (a type of light/electromagnetic wave), transmitting them through space, and converting them back to sound inside the astronaut's helmet where there is air.
Question 7: A classmate writes this evidence for the claim "Light travels in straight lines": "I think light goes straight because it makes sense." Explain what is wrong with this evidence and provide better evidence.
Answer: This is poor evidence because it is an opinion ("I think") and does not include any observations, measurements, or data. "Because it makes sense" is not evidence - it's a feeling.
Better evidence: "When sunlight shines through a small hole into a dusty room, you can see the light beam travels in a straight path. Shadows have sharp edges because light does not bend around objects. If you line up three cards with holes, light only passes through when all three holes are perfectly aligned in a straight line."
Question 8: What happens to a sound wave if you increase its amplitude? What happens if you increase its frequency? Describe both changes.
Answer: Increasing amplitude: The sound becomes louder. Amplitude represents the energy in the wave - more energy means more powerful vibrations, which we perceive as greater volume. The pitch stays the same.
Increasing frequency: The sound becomes higher-pitched. Frequency is how many vibrations occur per second - more vibrations mean a higher pitch (like a whistle vs. a drum). The loudness stays the same unless amplitude also changes.
Question 9: A scientist measures that sound takes 0.5 seconds to travel through 750 meters of a mystery material. Calculate the speed of sound in this material and predict whether it is likely a gas, liquid, or solid.
Answer:
Calculation: Speed = Distance / Time = 750m / 0.5s = 1,500 m/s
Prediction: This material is most likely a liquid. The speed (1,500 m/s) is much faster than air (343 m/s) but slower than most solids like wood (3,850 m/s) or steel (5,960 m/s). It is very close to the speed of sound in water (1,480 m/s). The material could be water or a similar liquid.
Question 10: Write a complete CER response to explain why sound cannot travel through outer space.
Answer:
Claim: Sound cannot travel through outer space.
Evidence: In laboratory experiments, when air is pumped out of a sealed jar containing a ringing bell, the sound completely disappears even though the bell is still visibly vibrating. In space, astronauts must use radio communication because spoken words do not travel between them, even when standing close together during spacewalks.
Reasoning: Sound is a mechanical wave that works by making particles vibrate and bump into neighboring particles, passing the vibration along. Outer space is a vacuum containing essentially no particles. Without particles to vibrate and collide, there is nothing to carry the sound wave from its source to a listener. This is fundamentally different from light, which is an electromagnetic wave that does not require particles to travel.
Self-Assessment
After completing the checkpoint, rate your understanding:
- 8-10 correct: Excellent! You have mastered the unit concepts.
- 6-7 correct: Good work! Review the topics where you struggled.
- 4-5 correct: Review the unit lessons before moving on.
- 0-3 correct: Go back through each lesson and retake the checkpoint.
Next Steps
- Review any concepts that felt challenging
- Revisit previous lessons in this unit if needed
- Move on to the next Science unit when ready
- Return to this checkpoint periodically for review