When a solution of hydrogen peroxide (H₂O₂) is heated, it undergoes decomposition. This means the H₂O₂ molecules break down into simpler substances. Here's what happens:

* Decomposition: H₂O₂ decomposes into water (H₂O) and oxygen gas (O₂).

* Reaction: 2 H₂O₂ → 2 H₂O + O₂

* Catalysis: This decomposition is accelerated by heat, and even more so in the presence of a catalyst like manganese dioxide (MnO₂).

* Observables: You'll notice bubbles forming in the solution as oxygen gas is released. The solution might also become cloudy or change color, depending on the concentration of the peroxide.

Important Note: Heating concentrated hydrogen peroxide solutions can be dangerous, as the decomposition reaction can be very exothermic and lead to a rapid release of oxygen, potentially causing a violent explosion. Always handle hydrogen peroxide with caution, following safety protocols.