Why is a fish considered an organism but a rock is not?

A fish is a living thing and a rock is not 

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.