When Pipes Leak and Chemistry Speaks
Recently, I had a plumbing problem. A leaky pipe appeared in the loft. At first, I assumed it was the joint — an easy fix. But no, it turned out to be the pipe itself. A tiny pinprick hole had eaten its way through the copper, leaving a little fountain in the loft tricking its way through the ceiling.
When we looked inside the pipe, we found a blue deposit clinging to the metal. And that’s where the chemist in me took over. Forget the plumber — this was a job for science!
Why Did the Copper Pipe Corrode?
Copper is normally quite resistant to corrosion, which is why we use it for pipes. But over time, water, dissolved oxygen, and other ions (like chlorides from salts or impurities) can attack it. The result is corrosion, producing copper compounds — often blue or green in colour.
So what was this mysterious blue substance? At GCSE and A-Level Chemistry, that’s exactly the kind of problem you learn how to solve.
Step 1: Make Observations
The colour gives our first clue. Blue suggests a copper(II) compound. Copper(I) salts tend to be white, while copper(II) salts are usually vivid blue or green.
Step 2: Dissolve and Test
Take a small sample (if this were in the lab, not your plumbing!) and dissolve it in water. If it dissolves to give a blue solution, you’re likely dealing with a copper(II) salt.
Step 3: Flame Test
A classic GCSE experiment: put a little on a flame test wire. Copper compounds burn with a beautiful blue-green flame — a strong confirmation.
Step 4: Precipitation Reactions
Add sodium hydroxide solution to your blue solution. A blue precipitate of copper(II) hydroxide should form. This is a classic test for copper(II) ions, taught in GCSE Chemistry.
Step 5: More Advanced A-Level Analysis
At A-Level, students would go further. They might use:
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Ligand tests – adding ammonia gives the deep blue tetraamminecopper(II) complex, a gorgeous colour change that students never forget.
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Spectroscopy – flame emission spectroscopy or even UV-Vis spectroscopy to identify the metal ions precisely.
1. Test for Carbonates (CO₃²⁻)
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Method: Add dilute hydrochloric acid (HCl).
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Observation: If carbonate ions are present, you’ll see bubbling/fizzing as carbon dioxide gas is released.
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Confirm: Bubble the gas through limewater — it will turn cloudy.
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Equation:
2. Test for Sulfates (SO₄²⁻)
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Method: Add dilute hydrochloric acid (to remove interfering carbonates), then add barium chloride solution (BaCl₂).
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Observation: A white precipitate of barium sulfate forms if sulfate ions are present.
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Equation:
3. Test for Chlorides (Cl⁻)
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Method: Add dilute nitric acid (to remove carbonates), then add silver nitrate solution (AgNO₃).
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Observation: A white precipitate of silver chloride forms.
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Confirm: The precipitate dissolves in dilute ammonia solution.
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Equation:
Summary Table
| Ion to Test | Reagent | Positive Result |
|---|---|---|
| Carbonate (CO₃²⁻) | Dilute HCl | Effervescence, CO₂ turns limewater cloudy |
| Sulfate (SO₄²⁻) | BaCl₂ + HCl | White precipitate of BaSO₄ |
| Chloride (Cl⁻) | AgNO₃ + HNO₃ | White precipitate of AgCl (soluble in ammonia) |
So, in your plumbing pipe story:
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If adding acid caused fizzing → carbonate.
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If barium chloride gave a white precipitate → sulfate.
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If silver nitrate gave a white precipitate → chloride.
The Verdict
Most likely, the blue substance in the pipe was basic copper carbonate, the familiar green-blue corrosion product also known as patina. But with a few tests, a student could identify whether it was carbonate, hydroxide, or another copper(II) salt.
So my plumbing problem became an impromptu chemistry case study. It just goes to show: the science in your textbooks isn’t locked in the lab — it’s happening in your pipes, your kitchen, and all around you.
At Hemel Private Tuition, we like to bring chemistry alive with real-life examples like this — whether it’s a corroded pipe or a colourful test tube. After all, the best way to learn is when the science drips (sometimes literally) into everyday life.
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