Endothermic
An endothermic reaction cannot occur spontaneously, an input of energy is required in order for it to proceed. When endothermic reactions absorb energy, a temperature drop is measured during the reaction.
Photosynthesis is an example of an endothermic chemical reaction. In this process, plants use the energy from the sun to convert carbon dioxide and water into glucose and oxygen. This reaction requires 15MJ of energy (sunlight) for every kilogram of glucose that is produced:
6CO2(g) + H2O(l)
C6H12O6(aq) + 6O2(g)
See Also
Exothermic.