Dec 14, 2009
423
1
0
Status
Pre-Dental
Supercooled water aat -10 C degree can spontaneously walm to 0 C degree in a perfectly insulated container. This is possible because ->

answer is
some of the water freezes and this provides energy.

Someone can explain the detailed reasoning for the answer? Thank you
 

evanyou

7+ Year Member
Jan 26, 2010
161
2
141
Dallas, TX
Status
Dentist
Supercooled water aat -10 C degree can spontaneously walm to 0 C degree in a perfectly insulated container. This is possible because ->

answer is
some of the water freezes and this provides energy.

Someone can explain the detailed reasoning for the answer? Thank you
it's not hard to explain after I see what this answer's like :laugh:

so here it goes! First of all, freezing is exothermic rxn. how would i know? because we need to add heat to melt ice down, right (endothermic)? since delta H is state function, the reversible rxn has exactly
-deltaH value. let's think about boiling. we know when we want boil water to cook Ramen, we have to heat it up. so it's endorthermic. thus, condensing water vapor to water liquid actually releases heat.
FYI, heat of deposition(liquid->solid) realeaes heat.
Interestingly, since delta H is a state function, heat of fusion + heat of vaporization + heat of deposition = 0 because they come around to their original state.

here's one practical question. why do we sweat, when we want to coooooool down?