Question

A student sets up an experiment by placing a jar of cold water colored yellow over a jar of hot water colored blue. After a few minutes, the water turns green as the water in the two jars mixes.



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Which is the BEST explanation for this observation?



A.
The yellow water has less energy and is more dense so it moves downward. The blue water has more energy and is less dense so it moves upward. The water mixes due to conduction.

B.
The yellow water has less energy and is more dense so it moves downward. The blue water has more energy and is less dense so it moves upward. The water mixes due to convection.

C.
The yellow water has more energy and is less dense so it moves downward. The blue water has less energy and is more dense so it moves upward. The water mixes due to conduction.

D.
The yellow water has less energy and is less dense so it moves downward. The blue water has more energy and is more dense so it moves upward. The water mixes due to convection.

Answer 1

B.

The cold (yellow) water has lower thermal energy and is denser, so it sinks. The hot (blue) water has higher thermal energy and is less dense, so it rises. Those density-driven motions set up convection currents that mix the two layers, producing green water.