The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must happen at the molecular level?

Temperature is related to the average kinetic energy of the water molecules. Since the temperature drops from 50°C to 30°C, their average kinetic energy decreases, so the molecules move more slowly on average. Therefore, the best choice is “The molecules move more slowly and their average kinetic energy decreases.”

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