What are the attractive forces in a neutral fluid?

[rogerk8]

Hi!

I wonder about how for instance water temperature is changed with regard to applied heat.

You all know that if you take ice and heat it up temperture will climb until it reaches 0C.

When it reaches 0C it however stobs climbing in tempertaure regardless of how much heat you supply.

It is said that heat is needed to overcome the attractive forces of the molecules instead of just giving them higher speed (i.e Ek and thus temperature).

It is said that these attractive forces constitute a potential energy to be overcome before the molecules can move faster thus giving the fluid higher temperature, Ek.

I just wonder what these attractive forces are because as far I understand there is no attractive forces between neutral molecules.

And regardless of state (solid, liquid or vapour) neutral H20 is still the molecule in mind.

So where is the attractive forces?

Roger

 

[jtbell]

as far I understand there is no attractive forces between neutral molecules.

Look up "van der Waals forces".

 

[rogerk8]

Van der Waal considers both the physical size of gas particles and "intermolecular attractions".

I have read this fantastic site: http://www.et.byu.edu/~rowley/ChEn273/Topics/Mass_Balances/Single_Phase_Systems/Van_der_Waals_Equation_of_State.htm

And it states that there are "intermolecular attractions".

But it never explains how or why.

So my question remains, how can there be intermolecular attractions between neutral molecules?

Roger

 

[rogerk8]

Another thing, I am interested in all the states of matter.

Van der Waal only considers the gas state.

Roger

 

[DrewD]

I can't answer in general, but at least water is a polar molecule. Taken as a whole it is neutral, but it isn't made of neutral particles. Since the particles are separated, it has a dipole electric field. I forget a kot of chem, but I bet a lot of intermolecular forces are electric forces due to uneven electon sharing.