When sugar is dissolve in tea, the reaction is accomplished by?

Analysis

The question asks about the thermodynamic change that occurs when a solid solute (sugar) dissolves in a solvent (tea/water). Specifically, it focuses on the concept of entropy.

Concept Explanation

Entropy ($S$) is a measure of the degree of disorder or randomness in a system.

• Solid state: Particles are tightly packed in an orderly arrangement, so entropy is low.
• Liquid/Solution state: Particles are free to move and are more randomly distributed, so entropy is higher.

When you dissolve sugar (a solid) into tea (a liquid), the sugar molecules break away from their rigid crystal lattice and disperse throughout the liquid. This transition from a highly ordered solid state to a more disordered, dispersed state in the solution represents an increase in entropy.

In thermodynamics, an increase in entropy is represented as a positive change ($\Delta S > 0$).

Step-by-Step Solution

1. Identify the system: We are moving from a solid (sugar) to a solution (sugar dissolved in tea).
2. Analyze the disorder: The sugar molecules move from a fixed, ordered position in the crystal to a random, disordered state in the liquid.
3. Relate to Entropy: Since the disorder of the system has increased, the change in entropy ($\Delta S$) is positive.
4. Evaluate the options: • A (positive change): This matches our finding that entropy increases. • B (negative entropy change): This would imply the system became more ordered, which is incorrect for dissolving a solid. • C (no entropy change): This is incorrect because the state of the sugar has clearly changed. • D (a minimum entropy change): This is not the standard thermodynamic description for the dissolution process.

Conclusion

The dissolution of sugar in tea leads to an increase in the randomness of the sugar molecules, which is defined as a positive change in entropy.

Exam Tip: Always remember the "Disorder Rule":

• Melting (solid to liquid) = Positive entropy change.
• Boiling (liquid to gas) = Positive entropy change.
• Dissolving a solid in a liquid = Positive entropy change.