Question

which phrase describes a sample of nacl(s)?

1. a mixture that has constant composition and properties throughout
2. a mixture that varies in both composition and properties
3. a substance that has constant composition and properties throughout
4. a substance that varies in both composition and properties

Explanation:

First, NaCl(s) (solid sodium chloride) is a pure substance (a compound), not a mixture. A pure substance has a constant composition (fixed ratio of Na⁺ and Cl⁻ ions) and uniform properties throughout. Mixtures have variable composition, so options 1 and 2 (which refer to mixtures) are incorrect. Option 4 is wrong because a substance (pure) does not vary in composition/properties. Option 3 correctly describes NaCl as a substance with constant composition and properties.

Answer:

1. a substance that has constant composition and properties throughout