Which of the following best describes when a physical change occurs?

• A. When atoms are rearranged to create new molecules.
• B. When energy is always absorbed and new chemical bonds are formed.
• C. When the form or appearance of a substance changes, but its chemical composition remains the same.
• D. When a substance is converted into a completely new substance with different chemical properties.

Answer: (C)

Verified step by step guidance

1. Understand the definition of a physical change: it is a change that affects the form or appearance of a substance without altering its chemical composition.
2. Recognize that in a physical change, the molecules or atoms themselves do not rearrange to form new substances; instead, only physical properties like shape, phase, or size may change.
3. Contrast this with a chemical change, where atoms are rearranged to create new molecules, resulting in substances with different chemical properties.
4. Note that energy changes can occur in both physical and chemical changes, but the key difference is whether new chemical bonds are formed or broken.
5. Therefore, the best description of a physical change is when the form or appearance of a substance changes, but its chemical composition remains the same.