In an exothermic reaction, energy is released from the system and into the surroundings, the system loses energy so the surroundings gain energy. The surroundings gain energy as heat and therefore there is a temperature increase. Exo- exitsystem releases energy, surroundings gain it as heat. In an endothermic reaction, energy is taken from the surroundings and into the system, the system gains energy while the surroundings lose energy. Energy is lost as heat therefore the temperature of the surroundings will decrease. Endo= insurroundings lose energy as heat, system gains energy.