Flame Tests

OCR

GCSE

Flame tests function as a fundamental qualitative analytical method for identifying specific metal cations through characteristic photon emission. The procedure necessitates the use of an inert nichrome or platinum wire and a non-luminous Bunsen flame to ensure accurate colour observation without carbon masking. Thermal energy excites electrons to higher energy levels; upon relaxation to the ground state, energy is released as visible light with specific wavelengths corresponding to the metal's unique electronic structure. Candidates must demonstrate mastery of the practical methodology and the theoretical basis of atomic emission.

Objectives

Exam Tips

Pitfalls

Key Terms

Mark Points

What You Need to Demonstrate

Key skills and knowledge for this topic

Award 1 mark for stating the nichrome or platinum wire must be cleaned with concentrated acid before use
Award 1 mark for identifying Lithium ions (Li+) produce a crimson flame
Award 1 mark for identifying Calcium ions (Ca2+) produce an orange-red flame
Award 1 mark for specifying the use of a non-luminous (roaring/blue) Bunsen flame to ensure color visibility
Award 1 mark for identifying Copper(II) ions (Cu2+) produce a green or blue-green flame

Example Examiner Feedback

Real feedback patterns examiners use when marking

"You correctly identified the ion, but check your color description against the OCR specification—is it 'red' or 'crimson'?"
"Good description of the method, but you forgot to mention cleaning the wire. Why is this step crucial for valid results?"
"You've listed the colors well. Now, can you explain why a machine (flame photometry) might be better at this task than a human eye?"
"Remember to specify a 'blue' or 'roaring' flame; a yellow safety flame would mask the result and lose you the method mark."

Marking Points

Key points examiners look for in your answers

Award 1 mark for stating the nichrome or platinum wire must be cleaned with concentrated acid before use
Award 1 mark for identifying Lithium ions (Li+) produce a crimson flame
Award 1 mark for identifying Calcium ions (Ca2+) produce an orange-red flame
Award 1 mark for specifying the use of a non-luminous (roaring/blue) Bunsen flame to ensure color visibility
Award 1 mark for identifying Copper(II) ions (Cu2+) produce a green or blue-green flame

Examiner Tips

Expert advice for maximising your marks

💡Memorize the exact OCR color descriptors: Lithium is 'Crimson', Calcium is 'Orange-red'. 'Red' is often rejected as too vague.
💡When describing the method, explicitly state 'dip the wire in acid' and 'place in a blue flame'. The type of flame is a critical marking point.
💡For Higher Tier, be prepared to compare flame tests with flame photometry, focusing on the machine's sensitivity, speed, and accuracy.

Common Mistakes

Pitfalls to avoid in your exam answers

Describing the flame color for Sodium as 'orange' (examiners strictly require 'yellow')
Confusing Lithium (crimson) with Calcium (orange-red) or Strontium (red) due to imprecise color terminology
Omitting the cleaning step between tests, which leads to contamination and mixed flame colors
Describing the method as 'burning the solid' rather than introducing a sample on a wire into the flame

Key Terminology

Essential terms to know

Qualitative identification of metal cations

Electron excitation and photon emission mechanisms

Experimental protocols and contamination control

Differentiation between manual tests and instrumental spectroscopy

Likely Command Words

How questions on this topic are typically asked

Describe

Identify

Compare

Explain

Suggest

Practical Links

Related required practicals

•{"code":"PAG C7","title":"Qualitative Analysis","relevance":"Practical investigation into identifying cations using flame tests"}

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