Question

which statement describes all chemical changes, but not all physical changes?
bubbles are produced.
a new substance forms.
phase changes occur.
a color change occurs.

Explanation:

• Bubbles produced: Can occur in physical changes (e.g., boiling water - gas bubbles from liquid to gas phase change).
• A new substance forms: Defines a chemical change (chemical reaction leads to new chemical identity), not a physical change (physical changes involve state, shape etc. but same substance).
• Phase changes occur: Defines physical changes (solid - liquid - gas transitions of same substance).
• Color change occurs: Can be physical (e.g., mixing colored solutions - no new substance) or chemical.

Answer:

A new substance forms.