When a substance undergoes a phase change, the mass

increases

decreases

stays the same

increases or decreases depending on the phase change

The answer is "stays the same".

Whether what kind of process the substance undergoes, the mass will stay the same. When a substance undergoes a phase change, the weight of the substance would either increases or decreases but the mass will definitely stay the same.

Well,what i learned was that unlike many other  endothermic  reactions,  photosynthesis  does not absorb energy as heat. instead, during plants absorb energy from sunlight to turn carbon dioxide and water into oxygen and glucose, which is a type of sugar molecule. the energy is stored in the glucose molecules, ready to be used when needed.