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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

Identify metal ions with flame tests and precipitates

Chemical reactions, acids and bases

CCSS NGSS.HS-PS1-2CCSS NGSS.SEP 3England: GCSE Chemistry: Chemical analysis (identification of ions)

Objective and success criteria

Students will: Identify metal ions with flame tests and precipitates.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Identify gases with laboratory tests

Leads to: the next skill in this area.

Materials: Teacher demo or video, Indicator color chart, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Identify gases with laboratory tests). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which gas gives this result: a lighted splint gives a squeaky pop? (hydrogen / oxygen / carbon dioxide / chlorine) → hydrogenPrompt: Each common gas has its own test.
  2. Why must the chlorine test be done in a fume cupboard? (Chlorine is invisible / Chlorine explodes / Chlorine is radioactive / Chlorine is toxic) → Chlorine is toxicPrompt: Think about safety.
  3. Tests for gases: which statement is NOT true? (Hydrogen gives a squeaky pop with a lighted splint. / Limewater is a solution of calcium hydroxide. / Chlorine turns limewater milky. / Chlorine may turn damp blue litmus red before bleaching it.) → Chlorine turns limewater milky.Prompt: Which gas pops and which relights a splint?

Hook · 3 min

  • Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
  • Share the objective: Identify metal ions with flame tests and precipitates. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: A flame test gives a lilac flame. Which metal ion is present?
  • Step 1: Potassium compounds give a lilac flame.
  • Step 2: So the answer is: potassium, K⁺
  • Answer: potassium, K⁺
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. A flame test gives a crimson flame. Which metal ion is present? (sodium, Na⁺ / lithium, Li⁺ / calcium, Ca²⁺ / copper, Cu²⁺) → lithium, Li⁺Prompt: Fireworks use these colours.
  2. Sodium hydroxide solution is added to a solution and a blue precipitate forms. Which metal ion is present? (copper(II), Cu²⁺ / iron(II), Fe²⁺ / iron(III), Fe³⁺ / calcium, magnesium or aluminium ions) → copper(II), Cu²⁺Prompt: Each transition metal ion gives its own coloured hydroxide.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Why should the wire loop be cleaned in acid before each flame test? (to remove traces of the last compound that could change the colour / to stop the wire melting / to make the flame hotter / to add sodium) → to remove traces of the last compound that could change the colourPrompt: Contamination gives false results.
  2. A flame test gives a yellow flame. Which metal ion is present? (lithium, Li⁺ / sodium, Na⁺ / copper, Cu²⁺ / calcium, Ca²⁺) → sodium, Na⁺Prompt: Fireworks use these colours.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Identify gases with laboratory tests.
  • Use concrete materials: teacher demo or video.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.

Free lesson plan from eurekami.com/lesson-plan-builder

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Identify metal ions with flame tests and precipitates

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Score/ 6

  1. Question 1

    A flame test gives a green flame. Which metal ion is present?

    • A. copper, Cu²⁺
    • B. potassium, K⁺
    • C. lithium, Li⁺
    • D. sodium, Na⁺

  2. Question 2

    Why can a flame test be hard to use for a mixture of sodium and potassium compounds?

    • A. Mixtures cannot be heated
    • B. Potassium does not give a flame colour
    • C. The colours combine into green
    • D. The bright yellow sodium flame can hide the lilac potassium colour

  3. Question 3

    Sodium hydroxide solution is added to a solution and a white precipitate forms. Which metal ion is present?

    • A. copper(II), Cu²⁺
    • B. iron(II), Fe²⁺
    • C. iron(III), Fe³⁺
    • D. calcium, magnesium or aluminium ions

  4. Question 4

    What advantage does flame emission spectroscopy have over a flame test by eye?

    • A. It works only on gases
    • B. It is less accurate
    • C. It is more sensitive and can measure the concentration of ions
    • D. It needs no flame

  5. Question 5

    Why should the wire loop be cleaned in acid before each flame test?

    • A. to make the flame hotter
    • B. to add sodium
    • C. to stop the wire melting
    • D. to remove traces of the last compound that could change the colour

  6. Question 6

    Sodium hydroxide solution is added to a solution and a brown precipitate forms. Which metal ion is present?

    • A. copper(II), Cu²⁺
    • B. iron(II), Fe²⁺
    • C. iron(III), Fe³⁺
    • D. calcium, magnesium or aluminium ions

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Answer key: Identify metal ions with flame tests and precipitates

  1. 1. A. copper, Cu²⁺

  2. 2. D. The bright yellow sodium flame can hide the lilac potassium colour

  3. 3. D. calcium, magnesium or aluminium ions

  4. 4. C. It is more sensitive and can measure the concentration of ions

  5. 5. D. to remove traces of the last compound that could change the colour

  6. 6. C. iron(III), Fe³⁺