5.1b Endothermic and exothermic reactions

Key things to memorize (more info below)

1. Exothermic = energy go out = negative (-) sign
   Endothermic = energy go in = positive (+) sign
   
   Make your own memoric device to remember this. Eg. Korean pop group "exo" has a lot of antifans so exo is (-)
    
2. Breaking apart = endothermic (because you have to put in energy)
   Forming bond/ coming together = exothermic
   
   Examples. H₂O (g) --> H₂O (l)  exothermic because molecules are clumping together
   
   
   Na (g) --> Na⁺ (g) + e-    endothermic because electron comes apart