Question
Sat April 02, 2011 By:

define endothermic and exothermic

Expert Reply
Sun April 03, 2011
Dear Student
 
Chemical reactions which release energy in the form of heat or light  are exothermic reactions. Exothermic reactions may occur spontaneously and result in higher entropy (ΔS > 0) of the system. They are denoted by a negative heat flow (heat is lost to the surroundings) and decrease in enthalpy (ΔH < 0). In the lab, exothermic reactions produce heat or may even be explosive.

There are other chemical reactions that must absorb energy in order to proceed. These are endothermic reactions. Endothermic reactions cannot occur spontaneously. Work must be done in order to get these reactions to occur. When endothermic reactions absorb energy, a temperature drop is measured during the reaction. Endothermic reactions are characterized by positive heat flow (into the reaction) and an increase in enthalpy (+ΔH).

 
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