Aboater sounds five short blasts on a horn. what does this signal mean?

If a boater sounds five short blasts on a horn, it represents danger, or that the boater does not understand the approaching boat's intentions. 
If the boater sees another boat approaching him, and he suspects that something fishy is going on, or he doesn't understand what the other boat is trying to do, he will sound five short blasts on his horn, in order to show that something is wrong. 

They immigrated for religious freedom

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen