Which of the following is NOT an example of a solution?

• A. Brass (an alloy of copper and zinc)
• B. Air (a mixture of gases)
• C. Salt water
• D. Sand and water

Answer: (D)

Verified step by step guidance

1. Understand the definition of a solution: A solution is a homogeneous mixture where the composition is uniform throughout, and the solute particles are dissolved at the molecular or ionic level in the solvent.
2. Analyze each option to determine if it fits the definition of a solution:
3. Brass is an alloy, which is a solid solution of copper and zinc metals, so it is a solution.
4. Air is a homogeneous mixture of gases, primarily nitrogen and oxygen, uniformly mixed, so it is a solution.
5. Salt water is a liquid solution where salt (solute) is dissolved uniformly in water (solvent), so it is a solution.
6. Sand and water is a heterogeneous mixture where sand particles do not dissolve but remain suspended or settle, so it is NOT a solution.