Claim-Evidence Writing
Learn
Scientists communicate their findings by making claims and supporting them with evidence. In this lesson, you will learn to write like a scientist using the CER framework: Claim, Evidence, and Reasoning.
The CER Framework
- Claim: A statement that answers a question or makes a conclusion
- Evidence: Data, observations, or facts that support your claim
- Reasoning: An explanation of how the evidence supports the claim using scientific principles
Writing Strong Claims
A good claim is:
- Specific and clear
- Answers the question directly
- Can be supported with evidence
Choosing Good Evidence
Strong evidence is:
- Relevant to your claim
- Based on observations or data
- Specific with details or numbers
Examples
Work through these examples to see the concepts in action.
Example CER Response
Question: What type of weathering caused the cracks in this desert rock?
Claim: The cracks in the desert rock were caused by physical weathering from temperature changes.
Evidence: The cracks follow a pattern radiating from the center. Deserts have extreme temperature differences between day and night, sometimes more than 40 degrees Fahrenheit.
Reasoning: Rocks expand when heated during the day and contract when cooled at night. This repeated expansion and contraction causes stress in the rock, which eventually leads to cracking. The radial pattern suggests the rock heated unevenly from the center.
✏️ Practice
Test your understanding with these practice questions.
Practice Questions
0/3 correctWhat is the scientific method's first step?
A hypothesis is:
Which is a property of matter?
Check Your Understanding
Test yourself with these review questions. Click on each question to reveal the answer.
1. What does CER stand for in scientific writing?
Answer: CER stands for Claim, Evidence, and Reasoning. It is a framework for organizing scientific explanations.
2. What is the difference between a claim and evidence?
Answer: A claim is a conclusion or answer to a question, while evidence is the data, observations, or facts that support that claim.
3. Which is a better claim: "Erosion is bad" or "Water erosion removes approximately 2 tons of soil per acre from this hillside each year"?
Answer: The second claim is better because it is specific, measurable, and can be supported with evidence. "Erosion is bad" is vague and opinion-based.
4. Why is reasoning important in scientific writing?
Answer: Reasoning connects the evidence to the claim by explaining HOW and WHY the evidence supports the claim using scientific principles. Without reasoning, readers do not understand the connection.
5. A student writes: "The Grand Canyon is deep." Is this a strong claim? Why or why not?
Answer: This is not a strong claim because it is vague and does not answer a scientific question. A stronger claim would be: "The Grand Canyon was primarily carved by water erosion from the Colorado River over millions of years."
6. What makes evidence "relevant" to a claim?
Answer: Relevant evidence directly relates to and supports the specific claim being made. It should address the same topic and help prove the claim is true.
7. Write a claim about why beaches often have smooth, rounded pebbles.
Answer: Example claim: Beach pebbles become smooth and rounded due to wave action that tumbles them against each other and the shoreline, wearing away rough edges over time through abrasion.
8. What is wrong with using the reasoning "because I think so" in scientific writing?
Answer: "Because I think so" is not scientific reasoning. Good reasoning must explain the connection using scientific principles, not personal opinions. It should explain HOW the evidence supports the claim based on what we know about how nature works.
9. How many pieces of evidence should you typically include to support a claim?
Answer: You should include at least 2-3 pieces of relevant evidence to make a strong argument. Multiple pieces of evidence from different sources make your claim more convincing and reliable.
10. Rewrite this weak statement as a strong CER response: "Glaciers make valleys."
Answer: Claim: Glaciers carve U-shaped valleys through erosion. Evidence: Valleys in glaciated areas have steep sides and flat bottoms, unlike the V-shape of river valleys. Scratches called striations are found on valley walls where glaciers passed. Reasoning: Glaciers are massive bodies of ice that slowly move downhill. As they move, they scrape and pluck rock from the sides and bottom, widening and deepening the valley into a characteristic U-shape.
Next Steps
- Review any concepts that felt challenging
- Move on to the next lesson when ready
- Return to practice problems periodically for review