revere reactions

[AMahadi]

Would the opposite phases changes (vapor to liquid, and liquid to solid) always be exothermic?

[madawy]

yes! Do go down a phase means to lose energy (ie how gas particles have much more energy than a solid). that energy is thus released in the form of heat.

[Diana Chavez-Carrillo 2L]

Would this be the same for going up a phase? Would it be endothermic in this case since now there is more heat required to break down the phase like a solid to liquid?

[Kayla Maldonado 1C]

Would this be the same for going up a phase? Would it be endothermic in this case since now there is more heat required to break down the phase like a solid to liquid?

Yes going up a phase requires energy to be absorbed otherwise defined as an endothermic reaction in order to go from a solid (low energy) to a liquid (higher energy).

[Shrayes Raman]

Going up a phase is akin to going up in energy levels so the correlation works both ways.

[Ashley Fang 2G]

To add to that, yes going down a phase is exothermic because from gas to liquid, water would release a great deal of energy.
This is the reason for severe steam burns that Dr. Lavelle was talking about last week in class.
It's also why sweating (evaporation of liquid water to gas) cools you down because it's endothermic.

[Hannah Romeo 1J]

In biology, photosynthesis and cellular respiration are reverse reactions. Cellular respiration is exothermic in that it produces ATP while photosynthesis is endothermic as it requires sunlight to proceed. Similarly, the reverse of all chemical reactions has the opposite form of heat (either released or absorbed) when compared to the forward reaction.

[pmokh14B]

Yes, they would just be the opposite sign of the phase changes that require energy (i.e (delta)Hfreezing, is -(delta)H melting)