| Show rr Much 1 uch Heat Required to Raise Rase Water Vater Temperature Water is is the great heat reservoir of the earth It takes more heat tc to raise the temperature of water ater b bj by bya r ra a given amount than is required for foi almost any other substance In ad ad- addition addition addition it take takes about 80 calories tc to melt a gram grain of ice and about tc to evaporate e an equal amount of ol water The same quantities quantifies ies of heal heat are released when the reverse changes chances the freezing of water anc and the condensation of water vapor take place according to Dr Thom Thomas as M. M Beck in the Chicago Tribune Water Vater spontaneously evaporates absorbing absorb ng the necessary heat from its surroundings until its vapor has reached a certain certain- pressure pre sure above which it cannot go When t the h e water vapor has reached this pressure pressure pressure pres pres- sure in air evaporation stops and the air is said to be saturated The vapor pressure of water is proportional proportional proportional to the amount of water ater held by saturated air and increases strongly with rising temperature Thus the pressure of water vapor m in in saturated air is about 2 inch at 32 degrees and increases to 12 inches at 85 degrees Our atmosphere is very rarely saturated however hoever Normally it il holds about 70 per cent of the amount theoretically possible This fraction of saturation is known as the degree of humidity When it is high very little evaporation takes place and when it is low the reverse reverse re- re I verse erse is true |
