Which statement applies to boiling but not to evaporation?

[coconut62]

"Which statement applies to boiling but not to evaporation?"

Homework Statement

Which statement applies to the boiling but not to the evaporation of a liquid?

A The separation of the molecules increases greatly
B At normal atmospheric pressure, the process occurs at one temperature only.
C Energy must be provided for the process to happen.
D All the bonds between molecules in the liquid are broken.

Homework Equations

None.

The Attempt at a Solution

I don't know, but to me B C D are all correct.

A is incorrect because: Boiling-Yes, Evaporation-Yes

B is correct because: Boiling-Yes, Evaporation-No (because occurs at all temperature)

C is correct because Boiling-Yes (supply heat to boil), Evaporation: No (Molecules with higher kinetic energies will just escape, no need to supply any energies to them)

D is correct because: Boiling-Yes (boiling occurs throughout the whole liquid, so all bonds broken), Evaporation-No (because I think that since only the fastest molecules escape, so it should not be "ALL bonds are broken".)

Can someone teach me about this? Thank you.

 

[Simon Bridge]

I don't know, but to me B C D are all correct.

It does not ask you which are correct though does it?
It asks: Which statement applies to the boiling but not to the evaporation of a liquid?
i.e. which ones are boiling-yes and evaporation-no?

 

[D H]

There's only one that has a "yes/no" answer.

With regard to C, why do you sweat? With regard to D, I think it was asking about the water that has boiled or evaporated off. (Besides, boiling is not explosive. It doesn't happen all at once. I ccan turn off the heat to a pot of boiling water and it stops boiling.)

 

[haruspex]

Because evaporation is a relatively slow process, you seem to have interpreted that side as merely some of the liquid evaporating. So you conclude evaporation does not satisfy D, and by imagining that the SVP at the liquid's initial temperature is above the ambient vapour pressure, some evaporation will occur without external input. OTOH, you've interpreted boiling as boiling all the liquid away. If you interpret evaporation as complete, you'll get different answers.

 

[Nickie]

Yes, B, C, and D are all correct statements for boiling but not for evaporation. Let's break down each statement to understand why.

A) The separation of molecules increases greatly.

This statement is incorrect because both boiling and evaporation involve the separation of molecules. In boiling, the entire liquid is heated and the molecules gain enough energy to break free from the liquid and become a gas. In evaporation, only the molecules on the surface of the liquid gain enough energy to break free and become a gas. So, in both cases, the molecules are separating.

B) At normal atmospheric pressure, the process occurs at one temperature only.

This statement is correct for boiling but not for evaporation. Boiling occurs at a specific temperature, known as the boiling point, for a given liquid at a given pressure. This means that no matter how much heat is applied, the liquid will not boil until it reaches the boiling point temperature. However, evaporation can occur at any temperature as long as the molecules on the surface of the liquid have enough energy to escape.

C) Energy must be provided for the process to happen.

This statement is correct for boiling but not for evaporation. In boiling, energy in the form of heat is required to raise the temperature of the liquid to the boiling point and to break the bonds between the molecules. In evaporation, the molecules on the surface of the liquid already have enough energy to escape, so no additional energy is needed.

D) All the bonds between molecules in the liquid are broken.

This statement is correct for boiling but not for evaporation. In boiling, the entire liquid is heated and the bonds between all the molecules are broken, allowing them to escape as a gas. In evaporation, only the molecules on the surface of the liquid have enough energy to escape, so not all the bonds between the molecules are broken. Only the bonds of the molecules on the surface are broken, while the molecules deeper in the liquid remain bonded to each other.

I hope this helps to clarify the differences between boiling and evaporation.