Science Argument Reference Sheet
CER Reference Sheet
Claim, Evidence & Reasoning Guide to Writing
Name:
Period:
The CER Formula:
Claim + Evidence + Reasoning = Scientific Argument
1. Claim (C) What is your main point or answer?
Answers the guiding question
A clear, 1-sentence answer to the research question. Stated as a fact without "I think" or explanations.
Quality Checklist Directly answers the lab prompt Written as a bold fact (no "I think") Does not include data numbers or "because"
Sentence Starters
- ▸ The experimental data reveals that [independent variable] causes [dependent variable] to...
- ▸ When [condition is changed], the direct result is that...
- ▸ [Condition A] has a [greater / lesser / no] effect on [variable] compared to [Condition B].
2. Evidence (E) What facts or data support your claim?
Measurements, data & observations
Observable proof gathered during testing. Uses specific numbers, units, and clear comparisons.
Quality Checklist Includes specific numbers and units (g, s, °C) Compares control vs. experimental trials Pure factual data only (no explanations yet)
Sentence Starters
- ▸ According to the lab data in Trial [X], the [measurement] measured [number + unit]...
- ▸ When tested at [condition A], the average was [value], compared to [value] at [condition B].
- ▸ The data graph illustrates that as [variable] increased from [A] to [B], [result] changed by...
3. Reasoning (R) How does your evidence support your claim and why does it matter?
Connects data to science principles
The scientific bridge. Connects your evidence to your claim by explaining the scientific concepts, laws, and mechanisms.
Quality Checklist Names the scientific law, concept, or rule Explains the scientific mechanism behind numbers Directly links all evidence back to prove claim
Sentence Starters
- ▸ According to the scientific principle of [concept], when [condition happens]...
- ▸ This evidence supports the claim because particles / forces behave by...
- ▸ Because science establishes that [scientific rule], the recorded data proves that...
Remember: A complete argument always requires all 3 parts. Evidence without reasoning is just numbers!
Page 1 • See Page 2 for Exemplar
CER Example
Annotated Lab Exemplar & Strong vs. Weak Analysis
Middle School Lab Model
CER Example
Question: Does adding salt to water change its boiling temperature?
Combined Response: Adding table salt to water increases the temperature required for water to boil. In our investigation, pure tap water boiled at an average of 100.0°C across three trials, whereas water containing 15 grams of dissolved salt boiled at an average of 102.6°C. According to the principle of boiling point elevation, solute particles in a solution disrupt water molecules from reaching vapor pressure, requiring greater thermal energy to boil.
CLAIM BREAKDOWN
"Adding table salt raises boiling temperature."
Why it works: Directly answers the question in a single bold statement without "I think."
EVIDENCE BREAKDOWN
"Pure boiled at 100.0°C; 15g salt water boiled at 102.6°C."
Why it works: Compares control to experimental data with specific numbers and units (°C, g).
REASONING BREAKDOWN
"Solutes disrupt vapor pressure, requiring more thermal energy."
Why it works: Explicitly names the science principle and explains particle-level behavior.
Strong vs. Weak Comparison Guide
Claim
"I think salt makes water boil differently." (Vague opinion, no direction)
"Adding salt increases water's boiling point." (Direct, specific statement)
Evidence
"The salted water got way hotter than plain water." (No measurements or units)
"Salt water boiled at 102.6°C vs. plain at 100.0°C." (Exact metrics & units)
Reasoning
"This proves my claim because we saw bubbles at 102°C." (Repeats data, no science)
"Due to boiling point elevation, solute ions block vapor." (Explains mechanism)
Quick 5-Point Peer Review Rubric
Use before turning in your lab write-up
Claim (1 Point)
Answers question clearly without "I think" or reasoning words.
Evidence (2 Points)
Cites exact numbers, units, and compares test conditions.
Reasoning (2 Points)
Names science law/concept and explains the physical mechanism.
CER Binder Checklist
CER Checklist
Student Writing & Self-Assessment Guide
Name:
Period:
Claim (C) What is your main point or answer?
Answers the guiding question
Direct Answer: Directly and clearly answers the guiding research or lab question.
Statement of Fact: Written as a confident, complete sentence (not a question or fragment).
No Opinion Words: Does NOT use personal phrases like "I think", "I believe", or "maybe".
Stand-Alone Claim: Does NOT include data numbers, experimental trials, or "because" yet.
Evidence (E) What facts or data support your claim?
Measurements & data
Specific Measurements: Includes exact numbers and metric units (e.g., grams, seconds, °C, mL).
Clear Comparison: Directly compares experimental results against the control group or baseline.
Multiple Trials & Trends: References averages, repeated trials, or patterns from graphs/tables.
Pure Facts Only: Focuses strictly on observed data without explaining scientific reasons yet.
Reasoning (R) How does your evidence support your claim and why does it matter?
Science principles
Science Principle Named: Explicitly names the core science law, rule, concept, or theory.
Mechanism Explained: Explains the "why" and "how" (particle movement, energy, forces, reactions).
The Scientific Bridge: Explicitly connects the numerical evidence directly back to the claim.
No Simple Restatement: Does NOT just repeat the data numbers; explains the science behind them.
Goal: Every checkbox on this list should be checked off before turning in your scientific argument!
CER Lab Mastery
