Question

after the plastic divider is removed, the hot and cold water meet at a boundary, labeled above. how does this boundary change during the demonstration? a it freezes into a solid b it forms a sharp, vertical line c it disappears as water evaporates d it moves as water changes place

Explanation:

When the divider is removed, hot and cold water mix due to diffusion (random molecular motion) and convection (movement from density differences: hot water is less dense, cold is denser). This mixing causes the initial boundary to shift as water layers change position. Freezing (A) is incorrect (no low temp), a sharp line (B) fades not forms, and disappearance from evaporation (C) is false (mixing, not evaporation, removes the boundary).

Answer:

D. It moves as water changes place