Which of the following samples of matter is classified as a solution?

• A. Salt water (NaCl dissolved in H2O)
• B. Sand and water mixture
• C. Oxygen gas (O2)
• D. Pure ice (solid H2O)

Answer: (A)

Verified step by step guidance

1. Understand the definition of a solution: A solution is a homogeneous mixture where one substance (the solute) is uniformly dissolved in another (the solvent).
2. Analyze each option to determine if it fits the definition of a solution:
3. For salt water (NaCl dissolved in H2O), recognize that salt (NaCl) dissolves completely in water, forming a uniform mixture at the molecular level, which is a classic example of a solution.
4. For sand and water mixture, note that sand does not dissolve in water and the mixture is heterogeneous, meaning the components are not uniformly distributed.
5. For oxygen gas (O2) and pure ice (solid H2O), identify that these are pure substances, not mixtures, so they do not qualify as solutions.