Question

why it is that evaporation causes cooling,but boiling causes heating?

Answer 1

HERE EVAPORATION IS A COOLING PROCESS 
EXAMPLE
SWEAT IN OUR BODY RELEASED IN THE FORM OF WATER DROPLETS THAT CARRY SOME OF OUR AWAY FROM OUR BODY WHICH MAKES US FEEL COOL
CONDENSATION IS A COOLING PROCESS BECAUSE DURING CONDENSATION THE VAPOUR IN THE SURROUNDINGS RELEASES HEAT AND GETS CONVERTED INTO LIQUID WHICH MAKES US FEEL WARM

Answer 2

Evaporation is one of the four principal ways that heat can be transferred (the other three are radiation, convection, and conduction).but For a liquid to turn into gas, either by boiling or evaporation, energy is required.
 In the case of boiling this is provided by external heat sources but in the case of evaporation it has to come from within the liquid itself, thus cooling it
.