Defining Concentration: Amount of Solute in Solvent

The question asks for the term that defines the amount of solute dissolved in a particular solvent. This is the fundamental definition of concentration.

• Concentration: This term quantifies the amount of a substance (solute) present within a given amount of another substance (solvent or solution). It directly matches the definition provided in the question.

Why Other Options Are Incorrect

The other options describe different physical properties of liquids and do not relate to the amount of solute dissolved:

• Surface Tension: This refers to the cohesive force at the surface of a liquid, causing it to behave like an elastic membrane. It does not measure dissolved solute.
• Fluidity: This is the ability of a substance to flow easily. It is related to intermolecular forces but not directly to the amount of solute.
• Viscosity: This measures a fluid's resistance to flow. Like fluidity, it is an intrinsic property of the liquid itself or its solution but doesn't quantify the dissolved amount.

Therefore, concentration is the correct term.