Claim-Evidence Writing | Open Textbooks

Learn

Apply the CER (Claim-Evidence-Reasoning) framework to wave concepts. This lesson focuses on constructing scientific arguments about energy transfer, wave behavior, and the electromagnetic spectrum.

Writing About Waves Using CER

Claim: State a conclusion about wave behavior or properties
Evidence: Provide specific data, measurements, or observations
Reasoning: Explain using wave physics principles (v=fλ, energy relationships, etc.)

Examples

Work through these examples to see the concepts in action.

Example 1: Comparing Wave Types

Claim: Sound waves require a medium to travel, but light waves do not.

Evidence: In a vacuum chamber, a ringing bell becomes inaudible while a light remains visible. Sound cannot travel through space, but sunlight reaches Earth.

Reasoning: Sound is a mechanical wave that needs particles to transfer energy through compression and rarefaction. Light is an electromagnetic wave that can propagate through the oscillation of electric and magnetic fields without matter.

Example 2: Energy and Frequency

Claim: Ultraviolet radiation is more harmful to skin than visible light.

Evidence: UV radiation causes sunburn and can damage DNA, while visible light does not cause these effects.

Reasoning: UV light has higher frequency than visible light, and wave energy is proportional to frequency (E=hf). Higher energy photons can break chemical bonds in DNA molecules.

✏️ Practice

Test your understanding with these practice questions.

Practice Questions

0/3 correct

Question 1

What is the scientific method's first step?

A Conduct experiment

B Make a hypothesis

C Ask a question

D Draw conclusions

Explanation: The scientific method begins with asking a question about something you observe.

Question 2

A hypothesis is:

A A proven fact

B A testable prediction

C The final answer

D An observation

Explanation: A hypothesis is an educated guess or testable prediction that can be investigated.

Question 3

Which is a property of matter?

A Color

B Speed

C Direction

D Time

Explanation: Properties of matter include color, mass, volume, density, and texture.

Check Your Understanding

Test yourself with these 10 quiz questions.

Question 1: What makes a strong scientific claim about waves?

Answer: A strong claim is specific, testable, and directly answers a question about wave behavior using precise scientific language.

Question 2: What type of evidence best supports claims about wave energy?

Answer: Quantitative data such as frequency measurements, wavelength values, and energy calculations provide the strongest evidence.

Question 3: How would you connect evidence about frequency to a claim about energy?

Answer: Use the relationship E=hf to explain that higher frequency means higher energy, connecting measured frequency data to energy conclusions.

Question 4: What scientific principle explains why sound travels faster in solids than gases?

Answer: Particles in solids are closer together and more rigidly bonded, allowing vibrations to transfer more quickly between particles.

Question 5: Write a claim about the Doppler effect.

Answer: Example claim: "The frequency of a wave appears to change when the source or observer is moving relative to each other."

Question 6: What evidence would support the claim that microwaves heat food?

Answer: Water temperature increases when exposed to microwave radiation; microwaves match the resonant frequency of water molecules causing them to vibrate and generate heat.

Question 7: How do you address contradictory evidence in scientific writing?

Answer: Acknowledge the contradictory data, explain possible sources of error, or revise the claim to account for all evidence.

Question 8: What reasoning connects evidence about wavelength to claims about wave behavior?

Answer: Wavelength determines how waves interact with objects (diffraction, interference) and their ability to penetrate materials based on size relationships.

Question 9: Why is it important to use the wave equation in reasoning?

Answer: The wave equation (v=fλ) mathematically connects measurable quantities and provides a scientific basis for explaining relationships between wave properties.

Question 10: Construct a CER about why different EM waves have different uses.

Answer: Claim: Different EM waves are used for different purposes based on their properties. Evidence: X-rays penetrate soft tissue (medical imaging), radio waves travel long distances (communication), visible light allows us to see. Reasoning: Wavelength and frequency determine how waves interact with matter, their penetrating power, and energy levels.

Next Steps

Review any concepts that felt challenging
Move on to the Unit Checkpoint
Return to practice problems periodically for review