Epinephrine's Noob Questions

[epinephrine]

Hello,

I had so many noob-tastic questions that I decided to make up a thread 

Anyways for my first question I read that the definition of latent heat of vaporization is the amount of energy needed to change a fixed amount of liquid to a gas at its boiling temperature, and was wondering why would extra energy be required to "boil" something ? Wouldn't the heat energy produce sufficient kinetic energy for the molecules to vibrate and break free?

[123456k]

what do you mean by break free?

[epinephrine]

Oh sorry bad wording on my behalf 

What I mean was break the intermolecular forces of attraction.

[REBORN]

I don't get your Q? Latent heat of vaporization is the amount of energy required to change a fixed amount of water from a liquid to a gas at 100 degrees C.

Anyways can you explain why water is such a good solvent for polar and ionic substances?

[schnappy]

I understand the question but admittedly am puzzled myself. Year 11 chem is so :whogivesashit:

Water is a good solvent for polar substances because it is very polar. It's a 'V' shaped molecule - has a partial negative charge on one side and a negative charge on the other. Cations (positive ions) like to make out with the partially negative oxygen side of a water molecule, anions (negative ions) like to rub up with the partially positive hydrogen atoms in a water molecule. Eg. NaCl (s) ---H_2O---> Na+(aq) + Cl-(aq)

See the diagram I linked in your NaCl thread.

[Mao]

Anyways for my first question I read that the definition of latent heat of vaporization is the amount of energy needed to change a fixed amount of liquid to a gas at its boiling temperature, and was wondering why would extra energy be required to "boil" something ? Wouldn't the heat energy produce sufficient kinetic energy for the molecules to vibrate and break free?

You can think of the boiling point as the temperature which molecules are moving at a critical speed. Any faster and the liquid will break apart, but at the critical speed it is sitting on the verge of becoming a gas, but doesn't actually have to become a gas. So the kinetic energy is not sufficient to boil something. Energy must be continuously added until ALL the molecules are promoted to beyond this critical kinetic threshold.

[epinephrine]

OMG Thank you soo much Mao it finally makes sense 

Oh and I was wondering how is energy released when ions are hydrated?

[Graphite]

Dissociation - Endothermic => energy absorbed
Solvation - Exothermic => energy released

Overall? Depends on magnitude of both variables

[epinephrine]

Thank you but I asked HOW is energy released ? happen to know? I gave it a quick google search and came up with
Enthalpy of hydration   

[Graphite]

Formation of bonds as I said it depends though, if energy the break bonds is greater then there is no energy released.
But yeah, formation of bonds is the process that releases heat, however it would be captured by the endothermic process happening simultaneously

[epinephrine]

OMG thank you sooo much