Reactivity 3 — What are the mechanisms of chemical change?
Inquiry 3: Concluding and evaluating — IB Chemistry SL Revision Notes & Topical Questions
10 min read 16 parts Lesson 11 of 12 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Lesson summary
Inquiry 3: Drawing conclusions — IB CHEMISTRY SL notes: Write a concise, evidence-based conclusion that answers the research question, compares with literature values and comments on uncertainty.Definition — a brief, focused summary of the findings.Aim — a clear, concise answer t…
- Broader link
- Nothing new
- Direct answer
- Supporting evidence
- Final result
- Support or refute
Part 1 of 7Purpose of a conclusion
Definition
- Definition a brief, focused summary of the findings.
Aim
- Aim a clear, concise answer to the research question, based only on evidence from the data analysis.
Broader link
- Broader link a strong conclusion relates the findings to scientific principles and accepted values.
Nothing new
- Nothing new no new ideas or explanations are introduced; it only summarises what was analysed.
Part 2 of 7Justifying the conclusion with data
Direct answer
- Direct answer start with a direct answer to the research question using the trend found in the interpretation.
Supporting evidence
- Supporting evidence quote key processed data such as a final concentration, a graph gradient or an experimental enthalpy change.
Fit
- Fit comment on how well the line fits the points, for example using R2.
Final result
- Final result always give the final result with its uncertainty.
Part 3 of 7Relating the result to the hypothesis
Support or refute
- Support or refute state explicitly whether the results support or refute the hypothesis.
Unsupported hypothesis
- Unsupported hypothesis this is a valid scientific finding and not a failed experiment.
Reasons
- Reasons reasons for a discrepancy are suggested in the evaluation.
Theory link
- Theory link connect the finding to the chemical theory, for example collision theory predicts that higher concentration gives more frequent effective collisions.
Limit of claim
- Limit of claim claim only what the data show; if the data are inconclusive, say so.
Part 4 of 7Comparing with accepted values
Literature value
- Literature value compare with values from the IB data booklet, textbooks or other reliable sources.
Cite the source
- Cite the source state the literature value and where it came from.
Quantify
- Quantify calculate the percentage error rather than saying the result was "close".
Accuracy
- Accuracy the comparison allows a comment on the accuracy of the outcome.
- Percentage error = (accepted value − experimental value) / accepted value × 100.
Part 5 of 7Impact of uncertainty on the conclusion
1Confidence
- Confidence the propagated uncertainty determines the confidence in the final result.
2Percentage error larger than percentage uncertainty
- Percentage error larger than percentage uncertainty the deviation is not just due to limits of the instruments.
- The main cause is likely a systematic error in the methodology.
3Literature value inside the uncertainty range
- Literature value inside the uncertainty range the result is consistent with the accepted value despite errors.
4Wording
- Wording say "consistent with" when only a limited range of values was tested, rather than "proves".
Part 6 of 7Structure of a strong conclusion
1
State what the data show, with a value and uncertainty.
2
Justify it with the trend, gradient or calculated value that supports it.
3
Link it to chemical theory.
4
Compare with the literature value using percentage error and uncertainty.
5
Keep it short and direct.
Part 7 of 7More from the specification
More from the specification
Evaluating experimental conclusions
- At the conclusion of a chemical investigation, students evaluate whether experimental results support the initial hypothesis regarding enthalpy of reaction or oxidation of alcohols.
Systematic errors vs random uncertainties
- Random uncertainties cause fluctuations around the mean,
- while systematic errors shift results consistently in one direction, significantly impacting accuracy.
- (such as heat loss or uncalibrated balances)
Identifying procedural weaknesses
- A thorough evaluation identifies specific procedural weaknesses in apparatus design,
- such as evaporative fuel loss or incomplete combustion when burning liquid alcohols in a spirit burner.
Realistic proposals for improvement
- Suggested modifications must be realistic and scientifically targeted,
- such as employing a copper draught shield, bomb calorimeter,
- or digital temperature logging to minimize heat dissipation.
Random error
- Unpredictable variation causing scatter, reduced by repeats.
Primary alcohol
- An alcohol in which the C–OH carbon is attached to one other carbon.
Improvement
- A specific change that addresses an identified weakness.
Weakness
- A feature of the method that leads to significant error.
Alcohol
- A compound containing –OH with a name ending in -ol.
Combustion
- Burning in oxygen
Limitation
- A factor that restricts the scope within which a conclusion is valid.
Calorimeter
- An insulated container used to measure temperature changes in reactions.
Key terms
| Term | Meaning |
|---|---|
| Conclusion | A summary answer to the research question based on the evidence. |
| Hypothesis | A testable prediction with a scientific explanation. |
| Percentage error | Difference between experimental and accepted value as a percentage of the accepted value. |
| Percentage uncertainty | Absolute uncertainty as a percentage of the measured value. |
| Coefficient of determination | R2, a measure of how well a line fits the data. |
| Literature value | An accepted value from a reliable source. |
Avoid these mistakes
1
Concluding more than the data show, such as claiming a rule for conditions that were not tested.
2
Failing to cite the source of a literature value.
3
Saying a result is "close" to the literature value instead of quantifying the percentage error.
4
Writing a conclusion that never answers the research question.
Last updated:
\n