Investigation planning and methods
- Syllabus
- 2024
- Topic
- —
- Level
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Learning objectives
—Devise and plan investigationsDevise and plan investigations, using scientific knowledge and understanding when selecting appropriate techniques.—Safe and appropriate experimental methodsDemonstrate or describe appropriate experimental and investigative methods, including safe and skilful practical techniques.
Devise a testable investigation plan
An investigation plan turns a scientific question into a method that can produce relevant evidence. Every choice of technique should follow from what must be changed, observed or measured.
| Planning decision | What to state | Why it matters |
|---|---|---|
| question and prediction | the relationship being tested and the expected outcome | keeps the evidence tied to a chemical idea |
| change and measurement | what will be changed and what result will be observed or measured | makes the investigation testable |
| conditions | which other relevant conditions will be kept consistent | prevents a second cause changing the result |
| technique and apparatus | a method with suitable range, precision and chemical compatibility | produces measurements or observations fit for the question |
| range and repetition | enough values to reveal a pattern and repeated measurements where appropriate | makes the proposed conclusion better supported |
| evidence decision | the comparison, graph or calculation that will answer the question | shows how results will test the prediction |
To test whether a deduction applies beyond one substance, repeat the same investigation with additional suitable substances while keeping the comparison method consistent. A wider evidence set can test the proposed general pattern.
Do not write a list of apparatus before defining the evidence needed. A valid plan is specific enough to follow, but detailed variable classification, recording conventions and evaluation belong to their own later skills and should not be substituted for the plan itself.
Choose and justify a safe experimental method
An appropriate experimental method uses apparatus and techniques that achieve the chemical purpose while controlling the specific hazards and avoidable losses in that experiment.
| Purpose | Appropriate choice or technique | Reason |
|---|---|---|
| measure a chosen liquid volume | measuring cylinder; use a pipette or burette when their precision or delivery function is required | match capacity and precision to the task |
| collect and measure a gas | gas syringe connected without leaks | records gas volume directly |
| evaporate solvent to form crystals | evaporating basin with controlled heating | provides a wide heated surface |
| show heating or reaction is complete | cool and weigh, then repeat heating, cooling and weighing until constant mass | unchanged mass shows no further measurable change |
| prevent droplets or solid leaving while gas escapes | a loose cotton-wool plug or suitable cover | reduces material loss without sealing a gas-producing vessel |
| Hazard | Control | Why the control fits |
|---|---|---|
| flammable liquid | remove naked flames; use indirect heating such as a water bath | reduces ignition risk |
| toxic gas | use a fume cupboard | contains and extracts the gas from the breathing zone |
| corrosive or irritating liquid | wear eye protection and avoid skin contact | reduces exposure to splashes |
Write safety as a linked pair: name the specific hazard, then the control that reduces exposure or ignition. Write apparatus choices as purpose → apparatus → reason, not as an unlabelled equipment list.
Never tightly seal an apparatus that produces or heats a gas. Do not claim that goggles control toxic inhalation or that a fume cupboard replaces careful handling; each control must match the actual route of harm.