liquid vs solid in kinetic energy of same temp...

[albertlee]

We know that temperature indicates the overall kinetic energy of an object, like air, water, metal, etc...

 

 

however, if air and water exist in room temperature, how come air remains gas while water remain liquid?

 

doesn't that contradict the kinetic theory of atoms which the particles in liquid have less kinetic energy than particles in gas??

[5614]

It's because different elements and different molecules have different boiling temperatures and this is due to the differing intermolecular forces.

 

In air there is a small intermolecular forces so little energy is required to seperate the molecules (ie. turn it into a gas) and so at a very low temperature air exists as a gas.

 

Compare this to the strong bonds in a metal... a lot of energy is needed to break these bonds, and consequently metal has a very boiling point.

[albertlee]

but if there exists stronger intermolecular forces between water than air, shouldn't the kinetic energy of water molecule slow down, so lower temperature, as it fits into the kineitc theory of atoms?

 

more over, what causes particles to move around? well, I know it's the heat energy, but how? electrons only move their orbits though..

[5614]

Why would a stronger intermolecular force slow things down? It just means as one molecule accelerates another molecule accelerates with it, ok, so it might slow the first molecule down... but there's 2 molecules (leading to a chain effect) moving instead of 1 molecule.

 

In a solid atoms can vibrate.

[swansont]

We know that temperature indicates the overall kinetic energy of an object' date=' like air, water, metal, etc...

[/quote']

 

Temperature indicates the average KE - there is a distribution. You will reach an equilibrium if you have say, a liquid and a gas of the same material - some molecules will evaporate, and some will condense.

 

But as 5614 said, the boiling points are different, and thermal equilibrium means the temperatures will be the same.

[BhavinB]

The kinetic theory of gases (atoms) assumes an ensemble of N non-interacting particles in a box of volume V.

 

The key is the word "non interacting". This assumption is not true for say water because there is heavy interaction through hydrogen bonds. A more accurate model will show that the kinetic energy of of water (in thermal equilibrium at room temperature) is not enough to break all the interactions that keep the water as a liquid.

[albertlee]

oh..thanks...

 

but, what is a "thermal equilibrium"?

[Klaynos]

oh..thanks...

 

but' date=' what is a "thermal equilibrium"?[/quote']

 

Very very very simply it is when all the systems are the same temperature...

[albertlee]

Alright...

 

thx for all the helps!