Some important points to remember as you complete this task: 1. speed is a scalar quantity and has only magnitude. velocity is a vector quantity and has both magnitude and direction. 2. average speed is defined as the distance traveled over the total time of travel. 3. average velocity is defined as the change in position (displacement) over the total time of travel.

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.