Investigating Catalysts Using Manganese Dioxide and Hydrogen Peroxide
A classic chemistry experiment that actually works – every time.
Catalysts can feel like one of those abstract chemistry ideas that students memorise but don’t really see. This experiment changes that instantly.
By adding manganese dioxide (MnO₂) to hydrogen peroxide (H₂O₂), students observe a rapid, dramatic reaction that clearly demonstrates what a catalyst does: speeding up a reaction without being used up.
It’s reliable, visual, safe when done properly, and perfect for GCSE and A-level chemistry.
The Chemistry Behind It
Hydrogen peroxide naturally decomposes very slowly:
2H₂O₂ (aq) → 2H₂O (l) + O₂ (g)
Manganese dioxide acts as a heterogeneous catalyst, providing a surface that lowers the activation energy of the reaction. The result is an immediate release of oxygen gas, visible as vigorous bubbling and foam.
Crucially:
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The MnO₂ is unchanged at the end
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The reaction is faster, not different
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Energy is released as heat (the tube warms noticeably - often enough to produce steam)
Method (Student-Friendly)
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Add hydrogen peroxide to a test tube or conical flask
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Carefully add a small spatula of manganese dioxide
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Observe the rapid effervescence
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Test the gas produced with a glowing splint (it relights → oxygen)
This works beautifully for live demonstrations, filmed lessons, or practical assessments.
What Students Can Investigate
This simple setup supports deeper scientific thinking:
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Comparing catalysed vs uncatalysed reactions
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Measuring rate of reaction (volume of gas or foam height vs time)
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Discussing activation energy using energy profile diagrams
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Reinforcing the definition of a catalyst for exam answers
It’s also a great opportunity to talk about industrial catalysts, linking the experiment to the Haber process, catalytic converters, and real-world chemistry.
Why I Use This Experiment
In my lab and online TV-studio lessons at Hemel Private Tuition, this experiment consistently:
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Engages even reluctant students
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Produces clear, repeatable results
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Makes “catalyst” more than just a definition
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Translates directly into stronger exam responses
It’s one of those experiments where students say:
“Oh… now I get it.”
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