2 H2O2(l) → 2 H2O(l) + O2(g) The exothermic process represented above is best classified as a — Bonding Chemistry Question

STEPS:

1. Compare the chemical identities of the reactant and the products:
* Reactant: Hydrogen peroxide ($\text{H}_2\text{O}_2$), a molecular liquid.
* Products: Water ($\text{H}_2\text{O}$), a molecular liquid, and oxygen gas ($\text{O}_2$), a diatomic gas.
* Because the starting material has been converted into entirely new substances with distinct chemical and physical properties, this process is fundamentally a chemical change rather than a physical change.

2. Recall the definition of a chemical change at the atomic/molecular level:
* A chemical change involves the rearrangement of atoms. This requires the breaking of existing intramolecular forces (chemical bonds) within the reactant molecules and the forming of new intramolecular forces (chemical bonds) to produce the products.
* A physical change, by contrast, alters only the physical state or intermolecular spacing of a substance (such as melting ice to liquid water) without altering the covalent bonds holding the individual molecules together.

3. Analyze the bonding changes occurring in the reaction:
* In the reactant ($\text{H}_2\text{O}_2$), oxygen atoms are bonded to each other by a single covalent bond ($\text{H–O–O–H}$).
* In the products, the single covalent bonds between the oxygen atoms in $\text{H}_2\text{O}_2$ are broken.
* New covalent bonds are formed: $\text{O–H}$ single bonds within $\text{H}_2\text{O}$ molecules, and a strong $\text{O=O}$ double bond to create molecular oxygen gas ($\text{O}_2$).
* Because intramolecular covalent bonds are broken and new covalent bonds are formed, this is classified as a chemical change. This aligns perfectly with Option D.

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WHY_OTHERS_WRONG:

• Option A is incorrect: While the formation of a gas (a "new phase") from liquid reactants is a common physical observation of this chemical reaction, the appearance of a new phase does not *define* a physical change. In a true physical phase change (e.g., boiling water), the molecular identity of the substance ($\text{H}_2\text{O}$) remains identical before and after. Here, the molecules themselves have changed.
• Option B is incorrect: This process is not a physical release of dissolved gas. The reactant starts as pure liquid hydrogen peroxide ($\text{H}_2\text{O}_2(l)$). The $\text{O}_2(g)$ is created from a chemical decomposition reaction, not simply escaping from a mixture where it was previously dissolved.
• Option C is incorrect: While it is true that this is a chemical change and that entropy increases during the reaction (converting 2 moles of liquid into 2 moles of liquid and 1 mole of gas), the increase in entropy is not *why* it is classified as a chemical change. Many physical changes—such as the evaporation of liquid water or the melting of ice—also feature a significant increase in entropy.