Question

question 6 of 10
which of the following is the most likely sign that a chemical change has
happened?

a. a solid is crushed into very small pieces.

b. two liquids are mixed at room temperature and a gas forms.

c. salt is mixed into water, forming a solution.

d. liquid rests on a table overnight, and some evaporates.

Explanation:

To determine the sign of a chemical change, we analyze each option:

• Option A: Crushing a solid is a physical change (only size changes, no new substance).
• Option B: When two liquids mix and a gas forms, this indicates a new substance (gas) is produced, which is a key sign of a chemical change (e.g., a reaction like acid + carbonate → gas).
• Option C: Dissolving salt in water is a physical change (salt can be recovered by evaporation, no new substance).
• Option D: Evaporation of a liquid is a physical change (state change, no new substance).

Answer:

B. Two liquids are mixed at room temperature and a gas forms.