Which of the following is a definite indicator of a chemical change?
A.
The shape of a substance is changed.
B.
A new substance is formed.
C.
A substance is converted from a liquid to a gas.
D.
The change in a substance is reversible.

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.

Velocity is the speed of an object in a certain direction so you'd need to know speed and direction