Relationship between internal energy and PE and KE

[influx]

Hi,

Firstly, I'd like to thank PhysicsForums and its members for helping me during my last couple of visits (around 7 months ago). With your help I managed to achieve an A at AS Physics (a UK exam)!

I am doing some basic concepts on internal energy etc and I came across the following:

''Heating is when energy is transferred between two objects due to a temperature difference. For example, if you put your cold hand on a warm radiator, energy is transferred from the radiator to your hand. This increases the internal kinetic energy of the molecules of your hand and so your hand warms up.''

So when you heat something up, the internal kinetic energy increases (and therefore the temperature does) but what happens to the internal potential energy? Could someone explain in basic terms?

Also:

''As 2 molecules in an ideal gas approach each other, the repulsive forces between the molecules slow them down until momentarily both are stationery. ''

So do the molecules actually collide with each other or not? Also, since the above describes what happens in an ideal gas, could someone explain what happens in a non-ideal gas (if there is such a thing?)

Thanks :)

 

[rude man]

Hi,

Firstly, I'd like to thank PhysicsForums and its members for helping me during my last couple of visits (around 7 months ago). With your help I managed to achieve an A at AS Physics (a UK exam)!

I am doing some basic concepts on internal energy etc and I came across the following:

''Heating is when energy is transferred between two objects due to a temperature difference. For example, if you put your cold hand on a warm radiator, energy is transferred from the radiator to your hand. This increases the internal kinetic energy of the molecules of your hand and so your hand warms up.''

So when you heat something up, the internal kinetic energy increases (and therefore the temperature does) but what happens to the internal potential energy? Could someone explain in basic terms?

I have never heard of "internal potential energy" of atoms/molecules.

Also:

''As 2 molecules in an ideal gas approach each other, the repulsive forces between the molecules slow them down until momentarily both are stationery. ''

So do the molecules actually collide with each other or not? Also, since the above describes what happens in an ideal gas, could someone explain what happens in a non-ideal gas (if there is such a thing?)

Thanks :)

Not sure about the molecules colliding or not (looks like no), but yes there are non-ideal gases. Like, all of them! An ideal gas does not exist but gases at low pressure approximate the equation of state of an ideal gas very nearly, greatly simplifying computations.

 

[Chestermiller]

Hi,

Firstly, I'd like to thank PhysicsForums and its members for helping me during my last couple of visits (around 7 months ago). With your help I managed to achieve an A at AS Physics (a UK exam)!

I am doing some basic concepts on internal energy etc and I came across the following:

''Heating is when energy is transferred between two objects due to a temperature difference. For example, if you put your cold hand on a warm radiator, energy is transferred from the radiator to your hand. This increases the internal kinetic energy of the molecules of your hand and so your hand warms up.''

So when you heat something up, the internal kinetic energy increases (and therefore the temperature does) but what happens to the internal potential energy? Could someone explain in basic terms?

Also:

''As 2 molecules in an ideal gas approach each other, the repulsive forces between the molecules slow them down until momentarily both are stationery. ''

So do the molecules actually collide with each other or not? Also, since the above describes what happens in an ideal gas, could someone explain what happens in a non-ideal gas (if there is such a thing?)

Thanks :)

In the case of an ideal gas, the molecules are far enough apart that the potential energy due to binary interactions (i.e, repulsive forces) between molecules is negligible, and the internal energy is dominated by kinetic energy. For non-ideal gases, the molecules are close enough together that the potential energy of the molecular interactions makes a significant contribution to the internal energy.

The repulsive force when two molecules get very close to each other is sufficiently high that they don't actually touch, even if they approach each other at high speed. Still, this is referred to as a "collision."

 

[MrWarlock616]

From this video, molecules don't actually touch but get repelled with a large force and so it's a collision.

 

[Nickie]

I can explain the relationship between internal energy, potential energy, and kinetic energy in simple terms. Internal energy is the total energy of a system, which includes both kinetic energy (energy of motion) and potential energy (energy due to position or configuration). In the example of heating, the internal energy of your hand increases as energy is transferred from the warm radiator. This increase in internal energy can be seen as an increase in both kinetic energy (the molecules in your hand move faster) and potential energy (the molecules are now in a higher energy state).

In an ideal gas, the molecules do not collide with each other, but rather they move freely and do not interact with each other. However, in a non-ideal gas, there are attractive and repulsive forces between the molecules, which can cause them to collide and interact with each other. This can affect the internal energy of the system and lead to deviations from ideal gas behavior.

I hope this helps to clarify the relationship between internal energy, potential energy, and kinetic energy. Keep up the good work in your studies!