Exothermic and endothermic: heat pump

[Rosalindbungs]

For ppl with br gen chem, it is book 2 pg 159 bullet point 1. As a gas is compressed to liquid, I get that intermolecular forces are strengthened and increased, but why is heat released? Does that make an increase in imf's an exothermic reaction?

---

Members don't see this ad.

 

[BerkReviewTeach]

For ppl with br gen chem, it is book 2 pg 159 bullet point 1. As a gas is compressed to liquid, I get that intermolecular forces are strengthened and increased, but why is heat released? Does that make an increase in imf's an exothermic reaction?

When a gas converts to a liquid, it forms new intermolecular interactions (weak bonds for lack of a more accurate description). Bond formation is an exothermic process, so heat is released from the molecules to the environment. This is why steam burns are so much worse than hot water burns even though the steam and hot water are at the same temparature.

It might be easier to see in the opposite direction. Conversion of a liquid into a gas requires that you add energy into the system to break the intermolecular bonds, so it is endothermic. This is how perspiration works to cool you off.

 

[RocketSurgeon]

When a gas converts to a liquid, it forms new intermolecular interactions (weak bonds for lack of a more accurate description). Bond formation is an exothermic process, so heat is released from the molecules to the environment. This is why steam burns are so much worse than hot water burns even though the steam and hot water are at the same temparature.

It might be easier to see in the opposite direction. Conversion of a liquid into a gas requires that you add energy into the system to break the intermolecular bonds, so it is endothermic. This is how perspiration works to cool you off.

I dont know if I would phrase it like that...close but not quite...

water at 100C is still taking in heat and the temprature does not rise until all of the water in turned into vapor so of the total heat in the system (water at 100C) the thermal energy is going into converting the water into vapor but with the vapor all of the heat is "free" so all of it goes into burning you..!