What is a solution?

• A. A pure substance with fixed composition.
• B. A mixture where a solute is dissolved in a solvent.
• C. A method for distillation.
• D. A suspension of undissolved particles.

Answer: (B)

A solution is a homogeneous mixture formed when a solute is dissolved in a solvent, resulting in a uniform composition throughout. The key idea is that dissolved particles are distributed at the molecular level so you can’t see different components and the sample behaves as a single phase. This can involve solid solutes like salt in water, gases like oxygen in nitrogen, or liquids like ethanol in water.

Why this fits best: a solution is defined by the dissolution of a solute in a solvent, creating one phase with uniform composition. The other options describe different concepts: a pure substance has fixed composition and is not a mixture; distillation is a separation method, not a definition of a solution; a suspension contains undissolved particles that may settle out, so it isn’t a true solution.