[cyberphlak]

I think you would both benefit from and enjoy learning about enthalpy and entropy. In all cases, energy is either 1. remaining at rest, 2. being transferred into or away from something. No work can be done without energy. Since energy is never created or destroyed, it is only transferred. This simple explanation is a good place to start when considering the activity of energy force - to include heat.

[Geezer]

I think you would both benefit from and enjoy learning about enthalpy and entropy. In all cases, energy is either 1. remaining at rest, 2. being transferred into or away from something. No work can be done without energy. Since energy is never created or destroyed, it is only transferred. This simple explanation is a good place to start when considering the activity of energy force - to include heat.

Rats! I knew it. Sooner or later somebody was bound to bring up the "E" words (enthalpy and entropy). Apparently, due to some cruel genetic trick, or more likely sheer laziness, I have never been able to get my head around either term. Entropy, kind of, but Enthalpy?? I always assumed they were entirely artificial constructs designed to trap poor undergraduate students.

Is there an "Idiots Guide to Entropy and Enthalpy" somewhere? If there isn't, somebody could make a fortune selling them.

[cyberphlak]

It appears daunting at first glance. If you want to email me, I will send you some simple ways of looking at it. In short, lets use heat, a cold body will take heat from the environment around it just as a warm body will "give" heat to its environment. Nature seeks balance in all things and energy, in all its forms, is no exception.

Another example - electrolysis of water. Faraday correctly states that it takes a minimum of 1.23 volts to split the water molecule. This doesn't happen in your living room because there are no perfect electrolytes. On the other hand, if you put the solution in a hot environment, some of the energy for dissociation comes from the heat energy and now you see current flow at a lower voltages. How this occurs is explained by the "E" words.

[Titanscape]

It is a matter of the atomic strikes on atoms, how fast and how frequent.

If a hard ball is moving in a wide space, and "expanse" it seldom strikes things like another one, supposing there are lots there like gas molecules. But bring it closer and there are more hits. If in a metre it moves 5 times per second through it and it is then "confined" between a ten cm space, it strikes each block 50 times per second, I think. In atoms this gives greater heat. By compression.

Like with the Blackbird SR 71 which gets hot and expands traveling through cold air.

And look at spacecraft re-entry. Cold molecules hit hard and fast the surface of the craft, it gets hot.

Gas molecules have no wall sometimes, so they push out and expand and so cool, like breath, blown to cool food.

[Elton Hesbon]

the real question is why wouldn't gas cool when it expands? maybe its because of of the recitical matter in the particles naked to the eye but ever so evolving contrary to cinematic elusive propoganda yet profound enough to diliberate a stretch in an inutive colas.  molecules are  niether questioned  nor classified sorry if some of you might not understand yet I have done my best to be understood yet not enough to be reasoned with thank you for reading and hope you find knowledge in  incomp  air   

[lyner]

It is a matter of the atomic strikes on atoms, how fast and how frequent.

If a hard ball is moving in a wide space, and "expanse" it seldom strikes things like another one, supposing there are lots there like gas molecules. But bring it closer and there are more hits. If in a metre it moves 5 times per second through it and it is then "confined" between a ten cm space, it strikes each block 50 times per second, I think. In atoms this gives greater heat. By compression.

Like with the Blackbird SR 71 which gets hot and expands traveling through cold air.

And look at spacecraft re-entry. Cold molecules hit hard and fast the surface of the craft, it gets hot.

Gas molecules have no wall sometimes, so they push out and expand and so cool, like breath, blown to cool food.

But temperature is the average kinetic energy. Merely having more collisions doesn't affect the kinetic energy - if they are perfectly elastic. The energy is there when work is done against the gas. This work will normally result in faster molecules but, as was established earlier on in the thread, with non-ideal molecules, some energy will be transferred to electrical potential energy due to distortion of the molecules during the collisions and this may affect how much the average KE (temperature) actually increases.
Do you have a problem with that?

[Titanscape]

Yes, I find chemistry hard to understand, been a long time, and I did not grasp it well then either. Just my liking for a conversation.

[CZARCAR]

consider a balloon inside an insulated sphere with a thermometer. The pressure between the baloon & the sphere is lowered so the baloon expands....does the temp change?

[Phractality]

When you push down on the handle of a bicycle pump, the vertical motion of the piston causes the air molecules to bounce down faster, thus making them hotter. So heat is part of the potential energy of compressed air. After the air cools and you raise the handle, (assuming no gas was released) you don't get back as much energy as you put in because the cooler molecules are not hitting the piston as hard. They bounce off of the rising piston more slowly, so the air then becomes cold.

[Geezer]

When you push down on the handle of a bicycle pump, the vertical motion of the piston causes the air molecules to bounce down faster, thus making them hotter. So heat is part of the potential energy of compressed air. After the air cools and you raise the handle, (assuming no gas was released) you don't get back as much energy as you put in because the cooler molecules are not hitting the piston as hard. They bounce off of the rising piston more slowly, so the air then becomes cold.

If it was an actual bicycle pump, some of the air would be released into the tire and take heat with it.

If none of the air was released, as long as there in no heat loss from the pump, when the air expands, you will get all the energy back that went into compressing it.

[CZARCAR]

extramolecular friction?

[Bored chemist]

the real question is why wouldn't gas cool when it expands? maybe its because of of the recitical matter in the particles naked to the eye but ever so evolving contrary to cinematic elusive propoganda yet profound enough to diliberate a stretch in an inutive colas.  molecules are  niether questioned  nor classified sorry if some of you might not understand yet I have done my best to be understood yet not enough to be reasoned with thank you for reading and hope you find knowledge in  incomp  air   

Did anyone order salad?

[CZARCAR]

the real question is why wouldn't gas cool when it expands? maybe its because of of the recitical matter in the particles naked to the eye but ever so evolving contrary to cinematic elusive propoganda yet profound enough to diliberate a stretch in an inutive colas.  molecules are  niether questioned  nor classified sorry if some of you might not understand yet I have done my best to be understood yet not enough to be reasoned with thank you for reading and hope you find knowledge in  incomp  air   

Did anyone order salad?

yes, we ordered the brains alad with may or not nays