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### Heat versus work

Posted: Sun Jan 21, 2018 5:05 pm
I'm confused on what I need to know, relevently, about the difference between work and heat. I know that heat is the energy associated with the random motion of particles, and work is energy of ordered motion in one direction, but I'm still confused as to what that really means. Thanks in advance!

### Re: Heat versus work

Posted: Sun Jan 21, 2018 5:16 pm
Heat and work are similar in that they both describe energy transfer.
I think of work as referring to something more mechanical, like pushing a piston.
I think of heat as referring to the thermal process thats responsible for temperature differences.

### Re: Heat versus work

Posted: Sun Jan 21, 2018 5:19 pm
Heat is a form of energy that is transferred due to a temperature difference. Heat flows from a high temperature region to a lower temperature region. Temperature measures the flow of heat energy, or the speed of the random moving particles. Work is "the process of achieving motion against an opposing force" (section 8.2). If a system can do a lot of work, then it possesses a lot of energy. This energy of ordered motion is channeled in one direction in order to do work on of by the system.

### Re: Heat versus work

Posted: Sun Jan 21, 2018 6:49 pm
I found it interesting that although work and heat are interchangeable forms of energy, while work can be fully transferred into heat, the vice versa is not true. This is because if heat is fully transformed into work, it would violate the laws of entropy, i.e, a closed system's entropy cannot decrease.

### Re: Heat versus work

Posted: Sun Jan 21, 2018 8:31 pm
From the textbook: "The fundamental molecular difference between work and heat is related to the orderliness with which atoms in the surroundings move. When energy is transferred as work, the system moves molecules in the surroundings in a definite direction... During the transfer of energy as heat, the molecules in the surroundings are moved in random directions" p. 272

### Re: Heat versus work

Posted: Sun Jan 21, 2018 8:35 pm
Work is very similar to heat except that work has a direction (i.e energy is used to push a piston up) whereas heat is the random collision of fast and slow molecules, causing energy to be transferred from the faster moving molecules to the slower ones.

### Re: Heat versus work

Posted: Mon Jan 22, 2018 3:58 pm
Heat and work are both forms of energy. Heat is the energy associated with the random motion of particles, while work is the energy of ordered motion in a specific direction.

First Law: Heat and work contribute to the total energy of the system. ΔU = q + w
Second Law: Work can be transformed into heat, but heat cannot be transformed into work.