🔬 Intervention Lesson B

ESCAPE ROOM

Chemical Analysis: Can You Escape?

📋 BRIEFING: You're locked in the lab. A mystery compound has been found at a crime scene. To escape, you must identify unknown gases, crack the flame code, solve precipitate puzzles, and identify the mystery compound. Every test you've learned is a key. Use them all.

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🚨 Misconception Busters

Common Mistakes – Let's Fix Them!

These are the mistakes Y10 make most. Fix them before the puzzles!

❌ Burning vs Glowing splint

Students mix these up constantly! BURNING = flame visible. GLOWING = blown out, ember only.

✅ Burning → H₂ (pop). Glowing → O₂ (relights)

If it has a flame: burning splint for H₂. If just an ember: glowing splint for O₂.

❌ Li⁺ (red) vs Ca²⁺ (orange-red)

These look similar! Students confuse them in exams.

✅ Li = pure crimson RED. Ca = distinctly ORANGE-red

Think: Lipstick = pure red. Campfire = orange-red.

❌ Halide precipitate colours all look the same

Cl⁻, Br⁻, I⁻ all give precipitates with AgNO₃ but different colours!

✅ Gets darker going down the group

Cl⁻ = white | Br⁻ = cream | I⁻ = yellow. Remember: they get darker!

❌ Using HCl to acidify halide tests

HCl contains Cl⁻ ions → false positive!

✅ Use HNO₃ (nitric acid)

Nitric acid has no interfering ions. Always HNO₃ for halide tests!

🔓 Puzzle 1

Gas Test Lab

3 unknown gases. Run the correct test, see the result, identify each gas to unlock Puzzle 2!

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Gas A (colourless)

🔥 Burning splint

✨ Glowing splint

🧴 Limewater

📄 Damp litmus

This gas is:

H₂O₂CO₂

Gas B (colourless)

🔥 Burning splint

✨ Glowing splint

🧴 Limewater

📄 Damp litmus

This gas is:

H₂O₂CO₂

Gas C (pungent)

🔥 Burning splint

✨ Glowing splint

🧴 Limewater

📄 Damp litmus

This gas is:

NH₃Cl₂CO₂

👥 PEER TEACH: "Explain to your partner the difference between a burning splint and a glowing splint."

🔓 Puzzle 2

Crack the Flame Code

Match each flame to its metal ion. All 5 correct → Puzzle 3 unlocks!

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RED

YELLOW

LILAC

ORANGE-RED

BLUE-GREEN

👆 Click flame, then click matching ion:

🔓 Puzzle 3

Precipitate Challenge

4 unknowns. Run the correct test, observe, identify the ion.

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Solution 1

🧴 AgNO₃+HNO₃

🧫 BaCl₂+HCl

⚗️ Add HCl

Cl⁻Br⁻SO₄²⁻

Solution 2

🧴 AgNO₃+HNO₃

🧫 BaCl₂+HCl

⚗️ Add HCl

I⁻Cl⁻CO₃²⁻

Solution 3

🧴 AgNO₃+HNO₃

🧫 BaCl₂+HCl

⚗️ Add HCl

SO₄²⁻Br⁻I⁻

Powder 4

🧴 AgNO₃+HNO₃

🧫 BaCl₂+HCl

⚗️ Add HCl

CO₃²⁻Cl⁻SO₄²⁻

🔓 Final Puzzle

Mystery Compound X

Use ALL tests to identify both the cation AND anion!

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🧪 Unknown X: white solid, dissolves in water

🔥 Flame test

🧴 Acidified AgNO₃

🧫 Acidified BaCl₂

⚗️ Add HCl

💧 Anhydrous CuSO₄

[ Awaiting test results... ]

Cation (flame):

Li⁺Na⁺K⁺Ca²⁺Cu²⁺

Anion (reagent):

Cl⁻Br⁻I⁻SO₄²⁻CO₃²⁻

✍️ Worked Example

Watch Me Solve It – Unknown Compound

Before your independent work, see how to answer a compound-identification question.

📋 Question [4 marks]

"A compound gives a yellow flame and a white precipitate with acidified AgNO₃. (a) Name the cation [1]. (b) Name the anion [1]. (c) Name the compound [1]. (d) Why use HNO₃ not HCl? [1]"

✅ Model Answer

💡 Exam Pattern: Flame → cation. AgNO₃ → halide. BaCl₂ → sulfate. HCl fizz → carbonate.

📋 Detective Report

Independent Work

Complete independently.

Questions completed: 0/0

📗 Grades U–1 • Grade 2 challenge marked with ⭐

MCQ

1. Glowing splint relights. Gas is:

GLOWING = ember only (no flame). This gas makes it burst back alight

H₂O₂CO₂

MCQ

2. Na⁺ flame colour:

Na = Nacho yellow. The colour of crisps

RedYellowLilac

Short

3. Cl⁻ precipitate colour with AgNO₃?

Lightest to darkest: white → cream → yellow. Cl⁻ is the lightest

White.

Short

4. What happens to anhydrous CuSO₄ with water?

Anhydrous = without water. Adding water = colour comes back (white → blue)

White → blue.

Long

5. Gas makes squeaky pop. Name gas, test, write equation.

H₂ combustion: 2H₂ + O₂ → 2H₂O. The pop = tiny explosion

Hydrogen. Burning splint → squeaky pop. 2H₂ + O₂ → 2H₂O.

⭐ Exam [3 marks]

6. Yellow flame, white ppt with AgNO₃. (a) Cation [1]. (b) Anion [1]. (c) Compound name [1].

Yellow = Na⁺. White ppt = Cl⁻. Together = NaCl (table salt)

(a) Na⁺. (b) Cl⁻. (c) Sodium chloride (NaCl).

📙 Grades 1–2 • Grade 3 challenge marked with ⭐

MCQ

1. Br⁻ + AgNO₃ gives:

Not white (Cl⁻), not yellow (I⁻). The middle colour is...

WhiteCreamYellow

Short

2. Why HNO₃ not HCl for halide tests?

HCl would add Cl⁻ ions → AgNO₃ reacts with those → false positive!

HCl has Cl⁻ → false positive white precipitate.

Short

3. Difference between NH₃ and Cl₂ litmus tests.

NH₃ is alkaline (blue). Cl₂ is a bleach (white). Completely different results

NH₃: damp red litmus → blue. Cl₂: damp litmus → bleached white.

Long

4. Student tests NaCl then KCl – gets yellow both times. Problem and fix?

Wire still has Na⁺ on it. Na yellow is so strong it hides the lilac. Clean it!

Na⁺ contamination. Clean wire in conc. HCl until no colour, re-test.

⭐ Exam [4 marks]

5. Powder fizzes with HCl, limewater milky, orange-red flame. (a) Anion [1]. (b) Cation [1]. (c) Compound [1]. (d) Gas [1].

Fizz = CO₃²⁻. CO₂ confirmed by milky limewater. Orange-red = Ca²⁺

(a) CO₃²⁻. (b) Ca²⁺. (c) CaCO₃. (d) CO₂.

📘 Grades 3–4 • Grade 5 challenge marked with ⭐

MCQ

1. Ionic equation for I⁻ test:

Ag⁺(aq) + I⁻(aq) → AgI(s). Aqueous ions form a solid precipitate

Ag⁺+I⁻→AgIBa²⁺+I⁻→BaI₂

Short

2. Ionic equation for sulfate test + name precipitate.

Ba²⁺ + SO₄²⁻ → BaSO₄. Barium sulfate = white solid

Ba²⁺(aq)+SO₄²⁻(aq)→BaSO₄(s). Barium sulfate.

Short

3. Why do different metals give different flame colours?

Each element has UNIQUE electron energy levels → unique light wavelengths

Electrons excited → emit light of specific wavelength when falling back. Each element has unique energy levels.

Long

4. Design a systematic test for an unknown white compound.

Flame identifies CATION. Reagent tests identify ANION. Do flame first, then reagents

1. Dissolve. 2. Flame test → cation. 3. HCl → if fizzes + limewater milky → CO₃²⁻. 4. If no fizz: AgNO₃+HNO₃ → halide. 5. If no ppt: BaCl₂+HCl → SO₄²⁻.

⭐ Exam [6 marks]

5. Compound Y: lilac flame, no fizz, cream ppt with AgNO₃. (a) Cation+justify [2]. (b) Anion+justify [2]. (c) Name [1]. (d) Ionic equation [1].

K⁺ = lilac. Br⁻ = cream (AgBr). KBr. Equation: Ag⁺(aq) + Br⁻(aq) → AgBr(s)

(a) K⁺ — lilac flame. (b) Br⁻ — cream ppt = AgBr. (c) KBr. (d) Ag⁺+Br⁻→AgBr(s).

Intervention B – Knowledge Organiser

Gas Tests

Gas	Test	Result
H₂	Burning splint	Squeaky pop
O₂	Glowing splint	Relights
CO₂	Limewater	Turns milky
NH₃	Damp red litmus	Turns blue
Cl₂	Damp litmus	Bleached white

Flame Tests

Ion	Colour
Li⁺	Red
Na⁺	Yellow
K⁺	Lilac
Ca²⁺	Orange-red
Cu²⁺	Blue-green

Anion & Water Tests

Ion	Reagent	Result
Cl⁻	AgNO₃+HNO₃	White ppt
Br⁻	AgNO₃+HNO₃	Cream ppt
I⁻	AgNO₃+HNO₃	Yellow ppt
SO₄²⁻	BaCl₂+HCl	White ppt
CO₃²⁻	Dilute HCl	Fizzes; limewater milky
Water	Anhydrous CuSO₄	White→Blue

Warm-Up / Misconception Check

1. How do you test for hydrogen?

2. K⁺ flame colour?

3. Br⁻ precipitate colour with AgNO₃?

4. What happens to anhydrous CuSO₄ with water?

Puzzle Notes

Misconceptions corrected:

Puzzle 1 – Gas Tests:

Puzzle 2 – Flame Tests:

Puzzle 3 – Precipitates:

Puzzle 4 – Mystery Compound:

We Do: Evidence Collection

Gas	Test Used	Result
A
B
C

Flame	Ion
Red
Yellow
Lilac
Orange-red
Blue-green

📝 Word Bank (Foundation)

Use these words: hydrogen, oxygen, carbon dioxide, ammonia, chlorine, burning splint, glowing splint, squeaky pop, relights, limewater, milky, damp litmus, blue, bleached white, lithium, sodium, potassium, calcium, copper, red, yellow, lilac, orange-red, blue-green, chloride, bromide, iodide, sulfate, carbonate, white precipitate, cream precipitate, yellow precipitate, silver nitrate, barium chloride, fizzes, anhydrous

✍️ Sentence Starters

• To test for ___ gas, you use a...

• The positive result is...

• The ion ___ gives a ___ coloured flame

• A ___ precipitate with AgNO₃ means ___ is present

Scaffolding Sheet

Gas Tests

BURNING splint (flame) = H₂ (pop). GLOWING splint (ember) = O₂ (relights).

Damp litmus: NH₃ → blue | Cl₂ → bleached white.

Flame Memory Aids

Li = Lipstick red | Na = Nacho yellow | K = King's lilac | Ca = Campfire | Cu = Statue of Liberty blue-green

Halides

Cl⁻=White | Br⁻=Cream | I⁻=Yellow (darker going down!). Use HNO₃ NOT HCl!

Ionic Equations

Ag⁺+Cl⁻→AgCl | Ag⁺+Br⁻→AgBr | Ag⁺+I⁻→AgI | Ba²⁺+SO₄²⁻→BaSO₄

Detective Report – Foundation (Grades U–1)

Multiple Choice & Short Answer

1. Glowing splint relights: [ ] H₂ [ ] O₂ [ ] CO₂

2. Na⁺ flame: [ ] Red [ ] Yellow [ ] Lilac

3. Cl⁻ ppt colour?

4. Anhydrous CuSO₄ + water?

Long Answer

5. Gas → squeaky pop. Name gas, test, equation.

Exam-Style Questions

6. [3 marks] Yellow flame, white ppt AgNO₃. (a) Cation [1]. (b) Anion [1]. (c) Name [1].

Detective Report – Middle (Grades 1–2)

Multiple Choice & Short Answer

1. Br⁻+AgNO₃: [ ] White [ ] Cream [ ] Yellow

2. Why HNO₃ not HCl for halides?

3. NH₃ vs Cl₂ litmus tests?

Long Answer

4. NaCl then KCl – yellow both times. Problem + fix?

Exam-Style Questions

5. [4 marks] Fizzes HCl, limewater milky, orange-red flame. (a) Anion [1]. (b) Cation [1]. (c) Name [1]. (d) Gas [1].

Detective Report – Higher (Grades 3–4)

Multiple Choice & Short Answer

1. I⁻ ionic equation: [ ] Ag⁺+I⁻→AgI [ ] Ba²⁺+I⁻→BaI₂

2. Sulfate ionic equation + precipitate name.

3. Why different metals → different flame colours?

Long Answer

4. Design systematic test for unknown white compound.

Exam-Style Questions

5. [6 marks] Compound Y: lilac flame, no fizz, cream ppt AgNO₃. (a) Cation+justify [2]. (b) Anion+justify [2]. (c) Name [1]. (d) Ionic equation [1].

Exit – Foundation (U–1)

1. Burning splint tests for?

2. Cu²⁺ flame colour?

3. I⁻ ppt colour?

Exit – Middle (1–2)

1. Carbonate test (two steps).

2. Why clean wire between tests?

3. All three halide ppt colours.

Exit – Higher (3–4)

1. Ionic equation for Br⁻ test.

2. Why HNO₃ not HCl?

3. Lilac flame + white ppt BaCl₂. Identify fully.

ESCAPE ROOM

Common Mistakes – Let's Fix Them!

❌ Burning vs Glowing splint

✅ Burning → H₂ (pop). Glowing → O₂ (relights)

❌ Li⁺ (red) vs Ca²⁺ (orange-red)

✅ Li = pure crimson RED. Ca = distinctly ORANGE-red

❌ Halide precipitate colours all look the same

✅ Gets darker going down the group

❌ Using HCl to acidify halide tests

✅ Use HNO₃ (nitric acid)

Gas Test Lab

Gas A (colourless)

Gas B (colourless)

Gas C (pungent)

Crack the Flame Code

Precipitate Challenge

Solution 1

Solution 2

Solution 3

Powder 4

Mystery Compound X

🧪 Unknown X: white solid, dissolves in water

Watch Me Solve It – Unknown Compound

📋 Question [4 marks]

✅ Model Answer

Independent Work

🏆 Finished? Add your name:

RAG Rate Yourself

🏆 YOU ESCAPED! 🏆

🎯 Today I Mastered:

Intervention B – Knowledge Organiser

Gas Tests

Flame Tests

Anion & Water Tests

Warm-Up / Misconception Check

Puzzle Notes

We Do: Evidence Collection

📝 Word Bank (Foundation)

✍️ Sentence Starters

Scaffolding Sheet

Gas Tests

Flame Memory Aids

Halides

Ionic Equations

Detective Report – Foundation (Grades U–1)

Multiple Choice & Short Answer

Long Answer

Exam-Style Questions

Detective Report – Middle (Grades 1–2)

Multiple Choice & Short Answer

Long Answer

Exam-Style Questions

Detective Report – Higher (Grades 3–4)

Multiple Choice & Short Answer

Long Answer

Exam-Style Questions

Exit – Foundation (U–1)

Exit – Middle (1–2)

Exit – Higher (3–4)