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Year 11
AQA
Foundation

Instrumental analysis and flame tests: crimson for lithium

I can identify metal ions based on the colour of their flame tests and understand how instrumental analysis methods are used for detecting and identifying elements.

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Year 11
AQA
Foundation

Instrumental analysis and flame tests: crimson for lithium

I can identify metal ions based on the colour of their flame tests and understand how instrumental analysis methods are used for detecting and identifying elements.

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Share activities with pupils

Lesson details

Key learning points

  1. Positive ions burn with distinct colours that are visible when heated above a blue Bunsen flame.
  2. Unique flame emission spectra are produced for each positive metal ion.
  3. Instrumental methods are accurate, sensitive, and rapid for detecting and identifying elements and compounds.
  4. A spectrometer can split light from coloured flames into flame emission spectra.
  5. A spectrometer can measure more than one metal ion in a single solution and the concentration of each.

Common misconception

Flame colours are unique, even in mixtures.

Explain that strong colours, like sodium's yellow, can mask others. Use spectrometry to identify masked elements.

Keywords

  • Flame test - A test where a chemical put into a flame produces a characteristic colour (tests for metal ions).

  • Spectroscope - An instrument that separates light into its component wavelengths.

  • Ion - An ion is an atom or group of atoms with a positive or negative charge due to the loss or gain of electrons.

  • Concentration - The amount of a solute dissolved in a certain volume of solvent.

  • Calibration curve - A graph used to determine the concentration of a substance in a sample.

Ensure safety precautions are followed; use clean equipment to avoid contamination during flame tests.
Teacher tip

Equipment

Bunsen burner setup, 'unknown' metal salt samples to do flame tests, nichrome wire loops, dilute hydrochloric acid, beakers, matches.

Content guidance

  • Risk assessment required - chemicals
  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
Which of the following particles are not found in the nucleus of an atom?
protons and neutrons
electrons and protons
neutrons and electrons
Correct answer: electrons only
protons only
Q2.
What charge does an ion have if it has gained electrons?
positive
neutral
Correct answer: negative
Q3.
Which part of the atom is involved in chemical bonding?
Correct answer: electrons
neutrons
protons
the nucleus
Q4.
Which of the following is a general property of metals?
poor conductors of heat
brittle
Correct answer: good conductors of electricity
dull appearance
insulators
Q5.
Where are metals generally located on the periodic table?
top right
top left
bottom right
bottom right
Correct answer: left and centre
Q6.
What is an ion?
an atom that has lost or gained protons
a neutral atom
Correct answer: an atom that has lost or gained electrons
an atom with more protons than neutrons

Exit quiz

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6 Questions

Q1.
What is the purpose of a flame test?
To test for non-metal elements.
Correct answer: To identify metal ions by the colour of the flame.
To determine the conductivity of a metal.
To measure the temperature of a flame.
Q2.
What flame colour does potassium produce?
yellow
green
Correct answer: lilac
blue
Q3.
Why is it important to clean the wire loop before conducting a flame test?
To prevent the flame from extinguishing.
Correct answer: To avoid contamination from previous tests.
To increase the temperature of the flame.
To remove excess metal ions.
To test multiple ions at once.
Q4.
What happens to electrons in metal ions when they absorb energy from the flame?
They lose energy and stay at the same level.
Correct answer: They move to a higher energy level.
They leave the atom permanently.
They remain in the same orbit.
Q5.
Why do different metal ions produce different flame colours?
Correct answer: Due to different electron arrangements in each metal ion.
The flame temperature changes for each metal.
The test uses different flames for each metal.
Different ions release more light.
Q6.
What is emitted when electrons in metal ions return to their ground state after excitation?
heat
Correct answer: light
sound