Pe

[QuarkQuarkQuark2001]

When we immerse a heater into a beaker of water, the water molecules move and bump into each other more quickly and vigorously.Their kinetic energy is increased and thus the temperature rises.

What I want to ask is " Does adding heat into a beaker of water, its potential energy rise or remain constant ( not considering the latent heat)??Assume that rise from 25 degree Celsius to 50 degree Celsius.

 

My thought is that it doesn't change. Its because the specific heat capacity for water liquid state is constant from 1-100.

The intermolecular force is so great?

[QuarkQuarkQuark2001]

Anyone help me ?

[Dave]

I don't think the potential energy would change, it's just the average kinetic energy of the water molecules that changes.

[wolfson]

Kinetic energy increase, therefore potential energy decreases.

[Martin]

When we immerse a heater into a beaker of water' date=' the water molecules move and bump into each other more quickly and vigorously.Their kinetic energy is increased and thus the temperature rises.

[i']What I want to ask is " Does adding heat into a beaker of water, its potential energy rise or remain constant ( not considering the latent heat)??Assume that rise from 25 degree Celsius to 50 degree Celsius.[/i]

 

My thought is that it doesn't change. Its because the specific heat capacity for water liquid state is constant from 1-100.

The intermolecular force is so great?

 

when you ask about potential energy you need to specify what kind

(do you mean gravitational potential energy? do you mean chemical potential energy? electrical?)

 

supposing you mean gravitational and the beaker is on earth, in earth's gravity. Maybe it is at your house on a tabletop.

 

then there is a very tiny increase in potential energy (too small to be practical to measure) because for one thing the water expands so it rises slightly in the beaker and its center-of-mass is now higher

 

there is also a very tiny, unmeasurable, relativistic effect, the mass of the beaker of water increases very slightly with temperature according to E = m c²

It sounds ridiculous and too small to even mention but the heat energy you put into the water does increase its mass everso slightly so that increases the gravit. potential of the beaker of water

 

if you lowered it by string and pulley from tabletop down to floor level you could theoretically get a little bit more energy from it if the water had been warmed first.

 

------

there are also intra molecular forces and intermolecular

the molecules of water are not only moving more rapidly (K.E.) they are also farther apart (the water has expanded)

 

You mentioned this---so you doubtless understand that heating the water puts in a small amount of P.E. by way of widening average separations. But again it is, IMHO, better to neglect these amounts because they are so tiny.

-------

 

In my opinion the most sensible answer is to say no, there is no (appreciable) increase in P.E.

Because these effects are all so small.

I could be wrong tho, and maybe someone will improve on this.

[YT2095]

it is Potentialy capable of heating another item of equal volume and mass to 50% of it`s starting temp though, after that no heat or energy will be transfered, so yes, in that respect it DOES have "potential Energy".

[Dave]

To be fair, when the water starts boiling off, there will be a decrease in GPE because the beaker is losing mass; but that's besides the point.

[[Tycho?]]

Umm, potential energy might not be the best term for that, although im not sure what is.

 

Lets put it this way, the total energy of the system would not change (assuming no water leaves the pot of course).

[JaKiri]

'']Lets put it this way, the total energy of the system would not change (assuming no water leaves the pot of course).

 

Yes it would, you're putting energy in.

[QuarkQuarkQuark2001]

when you ask about potential energy you need to specify what kind

(do you mean gravitational potential energy? do you mean chemical potential energy? electrical?)

 

Actually, I want to ask the intermolecular forces (potential energy)

and I have typed it in my post.

Anyway, does it change?>

[Martin]

------

there are also intra molecular forces and intermolecular

the molecules of water are not only moving more rapidly (K.E.) they are also farther apart (the water has expanded)

 

You mentioned this---so you doubtless understand that heating the water puts in a small amount of P.E. by way of widening average separations. But again it is' date=' IMHO, better to neglect these amounts because they are so tiny.

-------

[/quote']

 

to the extent that the water has expanded

(against the pull of intermol. forces)

it has stored some potential energy of that kind

 

glad you mentioned it

 

it is a small amount compared with the (K.E.) heat energy of the molecules moving around faster

[[Tycho?]]

Yes it would, you're putting energy in.

 

 

If the system was just the pot of water. I should clarify, I was talking about the water plus the hot thing, whatever it was.... ummm, I just read over his first post again, and I think I am confused on what it is he is actually asking. I retract my statement then.