Question

question 8 of 10
which of the following is the best definition of a chemical change?

a. a change in a substance where a phase change occurs

b. a change in a substance where energy is conserved

c. a change in a substance where no new substance forms

d. a change in a substance where one or more new substances form

Explanation:

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

• Option A: Phase changes (like melting, freezing) are physical changes, not chemical changes. So A is incorrect.
• Option B: Energy conservation occurs in both physical and chemical changes, so this is not unique to chemical changes. B is incorrect.
• Option C: A change with no new substance forming is a physical change (e.g., cutting a paper, phase changes). Chemical changes require new substances, so C is incorrect.
• Option D: By definition, a chemical change involves the formation of one or more new substances (e.g., burning wood, rusting iron). This matches the core concept of a chemical change.

Answer:

D. A change in a substance where one or more new substances form