Clarification of Enthalpy and Constant Temperature

[Allison Budwig-2B]

Hi y'all,
I wasn't able to wrap my head around the concept of no temperature change during phase changes. Even though heat is being supplied, how is there no temperature change? I remember him giving an example of a heat bath and a test tube but that really just flew over my head.
Is anyone able to share their thought process about this concept?
I appreciate any answers greatly!

[Sara Shimabukuro 1A]

Hi!

I think Professor Lavelle meant that if a reaction is happening in which a system is losing heat, then the object will not become colder if surrounded by a hot water bath which will help maintain the temperature, meaning that there is no temperature change even though an exothermic reaction took place.

[Austin_Schwartz_1L]

Hello,
This is because the heat energy being supplied to the system is being used only for the phase change, which means it is being used to break the bonds between the molecules of the substance. When a substance sees a change in temperature, it is because the energy being supplied to it is being used to increase the kinetic energy of the particles of the substance, and this is not happening during phase change.
I hope this helps!

[Gabrielle Malte 2G]

Temperature is a measure of kinetic energy, that is the movement of molecules. During a phase change such as vaporization or melting, the heat that is being supplied is being used to break the bonds between the water molecules rather than impact their kinetic energy. As such, the temperature doesn't change, but the phase of the water does.

[Noa Popko 3I]

During a phase transition, the heat that is supplied is going toward breaking down the bonds between molecules rather than heating up the system, so there isn't any change in the temperature.

[Rena Wu 3E]

Hi Allison, during a phase change, the energy being provided in an endothermic reaction is being used to break the bonds of the compound to transition it from one phase to another. Therefore, the temperature won't change because there is no energy going towards the temperature. However, when the heat energy does cause an increase in temperature, we know that the kinetic energy of the molecules in the system are also increasing because of the direct relationship between temperature and kinetic energy Dr. Lavelle previously mentioned in lecture. Hope this helps!