Differentiate endothermic from exothermic reaction?and why;?

Question

is it that the solution becomes hot when;
1. pelletes of sodium hydroxide was dissolved in water?
2. dilute hydrochloric acid was mixed with dilute sodium hydroxide?
also why is it that the solution becomes cold when ammonium chloride crystals were dissolved in water?

Plsss Help!!!

Answer 1

See the following site for help.

http://www.newton.dep.anl.gov/askasci/chem00/chem00971.htm

Answer 2

Exothermic is when he is released whereas Endothermic is where heat is absorbed. Ex. Freezing. You go from a liquid state to a solid state. Thus releasing heat. Ex. Vaporization. You go from a liquid state to a gas state. Thus heat is absorbed Ex. An endothermic equation looks like this (excuse the quantities or the unbalanced equation, its just an example) NH3 + CO2 + 343 J ---> CH3 + NO2 Ex. An exothermic equation looks like this ( " ") C + O2 ---> CO2 Heat: -56 kcal