A 1.00 g charcoal sample from an ancient fire has a 14C activity of 11.2 disintegrations/min. A living tree has a 14C activity of 15.3 disintegrations/min per gram. The half-life of 14C is 5730 y. How old is the charcoal sample?

The rocks expand when there hot/warm  and contract when they are cold.

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.