Which type of reaction occurs when atoms or molecules rearrange to form new substances?

• A. Chemical reaction
• B. Physical change
• C. Phase transition
• D. Nuclear reaction

Answer: (A)

Verified step by step guidance

1. Understand the definitions of each option: A chemical reaction involves the rearrangement of atoms or molecules to form new substances with different properties.
2. Recognize that a physical change involves changes in the state or appearance of a substance without altering its chemical identity.
3. Know that a phase transition refers specifically to changes between solid, liquid, and gas states, such as melting or boiling, without changing the substance's chemical composition.
4. Identify that a nuclear reaction involves changes in the nucleus of an atom, leading to different elements or isotopes, which is different from rearranging atoms in molecules.
5. Conclude that the process where atoms or molecules rearrange to form new substances is best described as a chemical reaction.