Is the dissolution of calcium hydroxide exothermic or endothermic?

Exothermic: Heat is given off as one of the products. The container holding the reactants and the products gets hot during the reaction. Use approximately 5 mL of 6M HCl and add to a testtube containing a small peice of mossy Zn. Immediately place a thermometer in the testtube and you will see a quick rise in temperature. This rise in temperature indicates that heat is given off which is a clear sign of an exothermic reaction. Hope this helps!!