Question

students were asked to use a beaker and water to model how thermal convection cycles material below earths crust. which situation best models thermal convection? a when water is left in an open beaker for days, it will completely evaporate. b when water in a beaker is warmed in sunlight on a windowsill, water evaporates slowly on one side and quickly on the other side. c when water in a beaker is warmed in a microwave oven for too long, it will boil and eventually vaporize completely. d when water in a beaker is warmed over a small flame, uneven heating causes warmer water near the bottom to rise and replace cooler water near the surface, which then sinks.

Explanation:

Thermal convection is the transfer of heat by the movement of a fluid (in this case water). It occurs due to density differences caused by uneven heating. Warmer, less - dense fluid rises and cooler, denser fluid sinks. Option D describes this process as the uneven heating of water in a beaker over a small flame causes warmer water near the bottom to rise and cooler water near the surface to sink. Options A, B, and C mainly describe evaporation and boiling, which are different from the convection process.

Answer:

D. When water in a beaker is warmed over a small flame, uneven heating causes warmer water near the bottom to rise and replace cooler water near the surface, which then sinks.