Final answer:
The correct answer is (d) surface tension decreases, viscosity decreases. As temperature increases, molecular interactions are disrupted, leading to reduced surface tension and viscosity for liquids, while gas viscosity increases due to more energetic collisions.
Step-by-step explanation:
When the temperature of a liquid is increased, its surface tension generally decreases. This occurs because surface tension is a measure of the energy required to increase the surface area of a liquid. An increase in temperature adds energy to the system, disrupting the molecular interactions that hold the liquid together at the surface. As these molecules gain kinetic energy, they move more freely and are less able to maintain the tight packing required for high surface tension.
Similarly, as temperature increases, the viscosity of a liquid decreases. Viscosity can be thought of as a liquid's resistance to flow, which is overseen by cohesive forces among molecules. High temperatures cause molecules to move faster, reducing their ability to stick together, thus lowering the liquid's viscosity.
In contrast, the viscosity of a gas increases with temperature because the increased kinetic energy results in more frequent and energetic collisions between atoms and molecules, leading to greater resistance to flow.