Question

physical vs. chemical change quick check
which observation most likely indicates that only a chemical change has taken place? (1 point)
the shape changes.
the change cannot be reversed.
a reaction occurs.
states of matter changes.

Explanation:

• Shape change: Physical change. For example, molding clay changes its shape but no new substance is formed.
• Change cannot be reversed: Some physical changes (e.g., tearing paper) are not easily reversed, and some chemical changes (e.g., baking a cake) are also not easily reversed. So this is not a definitive indicator.
• A reaction occurs: Chemical change involves a chemical reaction where new substances are formed.
• States of matter change: Physical change. For example, water boiling (liquid to gas) is a physical change.

Answer:

A reaction occurs.