Which of the following best explains why melting an ice cube is considered a reversible physical change?

• A. Melting an ice cube produces new substances that can be converted back to ice.
• B. Melting is irreversible because energy is lost to the surroundings.
• C. The change involves breaking chemical bonds in H2O molecules.
• D. The process does not alter the chemical composition of H2O, allowing the water to refreeze into ice.

Answer: (D)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: Physical changes affect the form of a substance but not its chemical composition, while chemical changes result in new substances with different compositions.
2. Recognize that melting ice involves changing from solid (ice) to liquid (water), which is a change in physical state, not in chemical identity.
3. Note that during melting, the H2O molecules remain intact; no chemical bonds within the molecules are broken or formed, only intermolecular forces are overcome.
4. Since the chemical composition of H2O remains the same, the process can be reversed by removing heat, allowing water to refreeze back into ice.
5. Therefore, melting an ice cube is a reversible physical change because the substance's chemical identity is preserved and the process can be undone by changing temperature.