Energy Changes

[anthropos]

I have just learnt about endothermic and exothermic reactions. Um...since endothermic reactions absorb heat from the surroundings, why do the temperature of the solution drop after the reaction?

 

Is evaporation endothermic or exothermic? Sorry, I really don't know...Itry to Google for it but I have people saying it is exothermic while the others say it's endothermic. SIGH

[Yggdrasil]

In an endothermic reaction, thermal energy (heat) is converted into potential energy. An endothermic reaction will not increase the temperature of the system because the heat transfered from the surroundings does not heat the system; rather that heat is converted to potential energy, and does not contribute to the temperature of the system.

 

Evaporation is an endothermic process (it has a positive change in enthalpy). Thermal energy is needed to break the intermolecular bonds that exist between the molecules in the liquid in order to form a gas (which, in turn, has more potential energy).

[anthropos]

Thanks, yggdrasil. Now I have a better understanding of energy changes.