Question

1. what distinguishes a pure substance from a mixture?

a. substances are compounds, and mixtures are not
b. mixtures are groupings of elements, and compounds are not
c. samples of the same substance can have different intensive properties
d. mixtures can be separated physically, while compounds cannot.

Explanation:

• Option A: Pure substances include elements and compounds, so saying substances are only compounds is wrong.
• Option B: Mixtures can be of elements and/or compounds, and compounds are made of elements, so this is incorrect.
• Option C: Pure substances have uniform intensive properties (like density, boiling point) regardless of sample, so this is wrong.
• Option D: Mixtures have components physically combined, so they can be separated by physical methods (e.g., filtration, distillation). Compounds (a type of pure substance) require chemical methods to separate components, so this correctly distinguishes them.

Answer:

D. Mixtures can be separated physically, while compounds cannot.