An exothermic reaction is a type of reaction that dissipates heat as the reaction proceeds. This would mean that in a closed system, when a reaction proceeds and is endothermic, the temperature of the solution or the system would increase so as to maintain the equilibrium with the whole system.
Answer:The oxygen during photosynthesis comes from split water molecules. During photosynthesis, the plant absorbs water and carbon dioxide. After the absorption, the water molecules are disassembled and converted into sugar and oxygen.