CER Writing: Explaining Our Discoveries
Learn
Scientists do not just discover new things - they also explain what they learned to others! In this lesson, you will learn to write like a scientist using CER: Claim, Evidence, and Reasoning.
What is CER?
CER is a way to explain your scientific thinking. It has three parts:
C - Claim: What do you think is true? This is your answer to a question.
"I think that..." or "The answer is..."
E - Evidence: What did you observe or measure that supports your claim?
"I observed..." or "My data shows..."
R - Reasoning: Why does your evidence support your claim? Connect to what you learned.
"This makes sense because..." or "This proves my claim because..."
Why Use CER?
CER helps you:
- Organize your thinking clearly
- Use evidence (proof) to support your ideas
- Explain WHY something happens, not just WHAT happens
- Think and write like a real scientist!
Examples
Example 1: Shadows and the Sun
Question: When are shadows the longest during the day?
Claim: Shadows are longest in the morning and afternoon.
Evidence: I measured my shadow at 9 AM, 12 PM, and 3 PM. At 9 AM it was 8 hands long. At noon it was only 3 hands. At 3 PM it was 7 hands long.
Reasoning: This makes sense because when the sun is low in the sky (morning and afternoon), it makes long shadows. When the sun is high at noon, shadows are short.
Example 2: Day and Night
Question: Why do we have day and night?
Claim: We have day and night because the Earth spins.
Evidence: When I spin a ball in front of a flashlight, one side is lit up (day) and one side is dark (night). As the ball spins, different parts get light.
Reasoning: The Earth works like my ball. As it spins, our side of Earth faces the sun (day) and then turns away from the sun (night). This happens every 24 hours.
Example 3: Seasons
Question: Why is summer warmer than winter?
Claim: Summer is warmer because we get more hours of sunlight.
Evidence: In summer, the sun rises early and sets late. I can play outside until 8 PM! In winter, it gets dark at 5 PM.
Reasoning: More hours of sunlight means more time for the sun to warm the Earth. That is why summer days are warm and winter days are cold.
Practice
Complete these practice questions to build your CER writing skills.
1. What does the "C" in CER stand for?
2. What does the "E" in CER stand for?
3. What does the "R" in CER stand for?
4. Which part of CER tells what you observed or measured?
5. Read this statement: "I think we see the moon at night because it reflects the sun's light." Is this a Claim, Evidence, or Reasoning?
6. Read this statement: "The thermometer showed 85 degrees in summer and 35 degrees in winter." Is this a Claim, Evidence, or Reasoning?
7. Write a CLAIM to answer this question: "Does the sun move across the sky during the day?"
8. Write EVIDENCE you could collect to support your claim from question 7.
Think about what you could observe or measure.
9. A student writes: "Shadows are short at noon." What is missing from this CER?
Is there Evidence? Is there Reasoning?
10. Write a complete CER (all three parts) to answer: "Can you see the sun at night?"
11. Why is the Reasoning part of CER important?
Think about what Reasoning adds that Claim and Evidence do not.
12. Look at your shadow investigation from the last lesson. Write a CER about what you discovered.
Check Your Understanding
Answer these questions to make sure you understand CER writing.
Key Idea 1: CER stands for ___________, ___________, and ___________.
Key Idea 2: A Claim is your ___________ to a question.
Key Idea 3: Evidence is information from ___________ or ___________.
Key Idea 4: Reasoning explains ___________ your evidence supports your claim.
Next Steps
- Practice writing CER responses about the sun, moon, and Earth
- Use sentence starters: "I claim... My evidence is... This shows that..."
- Share your CER writing with a partner and give each other feedback
- Get ready for the Unit Checkpoint to show what you have learned!