Explain why chemists use instrumental methods of analysis rather than traditional chemical tests when identifying substances in forensic investigations.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Forensic scientists are often asked to identify unknown substances found at crime scenes. They must work quickly, accurately, and with very small amounts of sample.
Model answer (5 marks)
Instrumental methods are faster than traditional chemical tests, allowing rapid decision‑making at a crime scene.
Instrumental methods are more accurate and sensitive, giving reliable results even when the sample is contaminated or degraded.
They can analyse very small amounts of material, which is essential when only trace evidence is available.
Instrumental techniques can detect and quantify multiple substances simultaneously, identifying complex mixtures.
The data produced can be stored, processed and compared electronically, facilitating record‑keeping and cross‑checking with databases.
Instrumental methods are more accurate and sensitive, giving reliable results even when the sample is contaminated or degraded.
They can analyse very small amounts of material, which is essential when only trace evidence is available.
Instrumental techniques can detect and quantify multiple substances simultaneously, identifying complex mixtures.
The data produced can be stored, processed and compared electronically, facilitating record‑keeping and cross‑checking with databases.
Examiner tips
- Use the word ‘instrumental methods’ first, then list each point in order; keep each point concise and use exam‑specific terminology.
- Show the five points clearly, matching the mark scheme structure.
Common mistakes
- Confusing ‘traditional tests’ with ‘instrumental methods’ in the same sentence; avoid repetition of the same idea.
- Failing to mention the ability to analyse tiny samples or mixtures, which are key points in the scheme.
Mark scheme (5 marks)
- Instrumental methods are faster than traditional chemical tests
- Instrumental methods are more accurate / sensitive than traditional chemical tests
- Instrumental methods can identify substances using very small amounts / tiny samples
- Instrumental methods can identify mixtures / more than one substance at the same time
- Results from instrumental methods can be stored / processed / compared using a computer or database
Key terms in this question
instrumental methods · forensic
Related
- All WJEC A-Level Chemistry (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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