Decide exactly what you are trying to prove or explain. Highlight the key words in the question or conclusion.
Check: Can you summarise the claim in one short sentence?
Flowchart
Every scientific statement must be backed by evidence. Follow this route.
1) Identify the claim
2) Find the relevant data
Look through your results table, graph, or secondary sources for facts that relate to the claim (numbers, names, quotes).
Check: Have you selected information that directly supports or challenges the claim?
3) Explain how the evidence links to the claim
Use connective phrases such as “because”, “this shows that”, or “this means”. Mention repeats, averages, or references.
Check: Would someone else understand why the data proves your point?
4) Judge strength and reliability
Comment on how trustworthy the evidence is. Consider sample size, range, source credibility, and agreement with other evidence.
Check: Could stronger evidence exist? What would improve it?
Explanation
Evidence vs opinion
Evidence is measurable information collected through observation, experiments, or reliable sources. Opinion is what someone thinks or feels. Scientific writing relies on evidence, not opinions.
Types of evidence
- Primary data: Measurements you collected yourself (e.g., “Average reaction time was 0.23 s”).
- Secondary sources: Trusted information from books, websites, or scientific reports (e.g., “WHO (2021) states…”).
- Observations: Qualitative descriptions (“The leaves wilted after 12 hours”).
Quoting evidence effectively
Use sentence stems such as “The evidence for this is…”, “This is supported by…”, or “The graph shows…”. Always include numbers, dates, or named sources so the reader can trace your evidence.
Key Vocabulary
- Evidence: Information that supports or refutes a claim.
- Source: Where the information came from.
- Reliability: How trustworthy a piece of evidence is.
- Citation: A reference to the author, website, or organisation that provided the evidence.
- Corroborate: To confirm a piece of evidence using another source.
Why using evidence matters
Anyone can make a claim, but scientists convince others by backing statements with solid evidence. Using evidence shows critical thinking, honesty, and a respect for facts—skills that are essential for secondary school science and beyond.
Examples
Example 1: Referencing repeats
“The insulated cup cooled by only 5 A°C while the control cooled by 16 A°C (averages of three repeats), so insulation slowed heat loss.”
Example 2: Using range to judge strength
“Reaction times ranged from 0.22–0.27 s, which is a small spread, so the evidence is reliable.”
Example 3: Quoting secondary sources
“According to the Met Office (2023), coastal areas are windier due to reduced friction. This supports our observation that the beach anemometer recorded higher speeds.”
Example 4: Distinguishing opinion
“Although one pupil said the fizzy drink tasted ‘stronger’, this is an opinion. The evidence is that the gas produced measured 45 cm³ compared with 20 cm³ for water.”
Practice
Answer all questions, then check your answers. Your quiz result is saved on this device.
Common Mistakes
Mistake 1: Saying “I just know”
× Wrong: “The light was brighter because it looked brighter.”
? Right: “The light sensor reading increased from 260 to 410 lux.”
Mistake 2: Ignoring source quality
× Wrong: Citing an anonymous blog for medical facts.
? Right: Use organisations such as NHS, NASA, or peer-reviewed textbooks.
Mistake 3: Mixing evidence and opinion
× Wrong: “The solution turned blue, which was lovely.”
? Right: Keep observations factual and separate from personal reactions.
Mistake 4: Forgetting to mention repeats
× Wrong: Reporting only one measurement.
? Right: “This conclusion is based on the mean of three repeats, reducing the effect of errors.”
Summary
- State the claim, then present relevant data.
- Quote numbers, units, or named sources.
- Explain how the evidence supports (or challenges) the claim.
- Judge how strong the evidence is by considering repeats, range, or reliability of the source.
- Keep opinions separate from scientific statements.
Skills Checklist
- I can identify which data supports a claim.
- I can cite measurements, averages, or secondary sources correctly.
- I can explain why a piece of evidence is strong or weak.
- I can distinguish between fact and opinion in scientific writing.