CER Writing: Writing Like a Scientist
Learn
Scientists don't just do experiments - they also write about what they learn! In this lesson, you will learn how to explain your thinking like a real scientist using CER.
What Is CER?
CER stands for three important parts:
- C = Claim - What do you think is true? (Your answer)
- E = Evidence - What did you see or measure that proves it? (Your proof)
- R = Reasoning - Why does your evidence support your claim? (Your explanation)
C is for Claim
A claim is a sentence that answers a question. It tells what you think is true.
Question: Do plants need water to grow?
Claim: Plants need water to grow.
A good claim:
- Answers the question directly
- Is one clear sentence
- Does NOT use "I think" or "I believe"
E is for Evidence
Evidence is the proof from your investigation. It is what you SAW or MEASURED.
Evidence: The plant with water grew 6 inches tall and had green leaves. The plant without water did not grow at all.
Good evidence:
- Comes from your observations or data
- Uses numbers when possible (like 6 inches)
- Describes what actually happened
R is for Reasoning
Reasoning explains WHY your evidence proves your claim. It connects your proof to your answer.
Reasoning: This shows that plants need water because only the plant that got water was able to grow. Water helps plants stay healthy and make food.
Good reasoning:
- Uses the word "because" or "this shows that"
- Explains the connection between your evidence and claim
- Uses what you know about science
Putting CER Together
Here is a complete CER about plants and water:
Question: Do plants need water to grow?
Claim: Plants need water to grow.
Evidence: In our investigation, the plant with water grew 6 inches tall and had 8 green leaves. The plant without water stayed as a seed and did not grow at all.
Reasoning: This shows that plants need water because only the plant that got water was able to grow. Plants use water to make food and stay alive. Without water, the seed could not sprout.
Examples
Example 1: CER About Sunlight
Question: Do plants need sunlight?
Claim: Plants need sunlight to be healthy.
Evidence: Our plant in the sunny window was 5 inches tall with dark green leaves. Our plant in the closet grew 7 inches tall but had pale yellow leaves and fell over.
Reasoning: This shows that sunlight is important because even though the dark plant grew tall, it was weak and not green. Plants need sunlight to make their green color and grow strong. The plant in the dark stretched tall trying to find light but was not healthy.
Example 2: CER About Animal Needs
Question: Do fish need water?
Claim: Fish need water to survive.
Evidence: Fish live in water in fish tanks, ponds, and oceans. Fish have gills that only work in water. When fish are out of water, they cannot breathe.
Reasoning: This shows that fish must have water because their gills are made to get air from water. Fish breathe through their gills, just like we breathe through our nose and mouth. Without water, fish cannot get the air they need to live.
Example 3: Identifying Parts of CER
Read this CER. Can you find the claim, evidence, and reasoning?
"Dogs need food to have energy. My dog Max runs fast when he eats breakfast. When he skips a meal, he just wants to sleep. This proves that food gives dogs the energy they need to play and move around."
Answers:
- Claim: Dogs need food to have energy.
- Evidence: My dog Max runs fast when he eats breakfast. When he skips a meal, he just wants to sleep.
- Reasoning: This proves that food gives dogs the energy they need to play and move around.
Practice
Answer these questions about CER writing.
1. What does CER stand for?
A) Cats, Elephants, Rabbits
B) Claim, Evidence, Reasoning
C) Careful, Easy, Right
D) Count, Estimate, Record
2. What is a CLAIM?
A) A question you ask
B) Your answer that tells what you think is true
C) A drawing of your experiment
D) A list of materials you used
3. What is EVIDENCE?
A) A guess about what might happen
B) What you saw or measured that proves your claim
C) Your opinion about the experiment
D) The title of your project
4. What is REASONING?
A) The first step of an experiment
B) Drawing a picture
C) Explaining WHY your evidence supports your claim
D) Asking a question
5. Which is the BEST claim for the question "Do birds need food?"
A) I think birds are cool
B) Birds need food to survive
C) Maybe birds eat sometimes
D) I saw a bird yesterday
6. Which is an example of EVIDENCE about plants needing light?
A) I think plants like the sun
B) The plant in the sunny spot grew 4 inches, the plant in the dark grew 1 inch
C) Plants are green
D) Sunlight is warm
7. Read this sentence: "This shows that water is important because the plant with water grew bigger." This sentence is an example of:
A) A claim
B) Evidence
C) Reasoning
D) A question
8. What word often starts the REASONING part?
A) First
B) I think
C) Because or This shows that
D) Maybe
Read this CER for questions 9-10:
"Rabbits need water to stay healthy. Our classroom rabbit drinks from its water bottle many times each day. We measured that it drinks about 1 cup of water daily. This proves that rabbits need water regularly because their bodies use water to stay cool, digest food, and stay alive."
9. What is the CLAIM in this CER?
A) Our classroom rabbit drinks from its water bottle many times each day
B) Rabbits need water to stay healthy
C) We measured that it drinks about 1 cup of water daily
D) This proves that rabbits need water regularly
10. What is the EVIDENCE in this CER?
A) Rabbits need water to stay healthy
B) Our classroom rabbit drinks from its water bottle many times each day. We measured that it drinks about 1 cup of water daily.
C) This proves that rabbits need water regularly because their bodies use water
D) Rabbits are cute animals
11. Sara writes: "The plant grew 3 inches." This is an example of:
A) A claim
B) Evidence
C) Reasoning
D) A prediction
12. Why is it important to include REASONING in your CER?
A) To make your writing longer
B) To explain the connection between your evidence and your claim
C) To ask another question
D) To make a prediction
Check Your Understanding
Try writing your own CER! Use this question:
Question: Do plants need air?
Write a CER to answer this question. Remember to include:
- Claim: Your answer in one sentence
- Evidence: What you know or observed that proves it
- Reasoning: Why your evidence supports your claim
Challenge: Write a CER about what animals need to survive. Pick one animal and one need (food, water, air, or shelter).
Next Steps
- Practice finding claims, evidence, and reasoning in books you read
- Try writing a CER about something you notice at home
- Complete the Unit Checkpoint to show what you have learned about plants and animals