phase changes [ENDORSED]

[Amanda Salgado 3D]

Just to clarify, when going from up from a solid, to liquid, to gas...the result is a positive number, and when going down from a gas, to a liquid, to a solid, the result is a negative number?

[Caitlin Dillon 3G]

Correct. In order for a solid to go to a liquid, it must absorb heat, so it is endothermic and positive delta H. When a liquid goes to a solid, it must release heat, so it is exothermic and negative delta H.

[yoonjong_han_3F]

So, as Dr. Lavelle mentioned in lecture,

when you touch the object at 100 celsius, there will be transfer of heat to your hand! So, it is exothermic

[Yasmine Choroomi 2C]

Going from a solid to a liquid is endothermic and heat is absorbed! because we look at everything in terms of the system, delta H is positive because heat must go in!