work definition


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Jack Papciak 2F
Posts: 31
Joined: Fri Sep 29, 2017 7:06 am

work definition

Postby Jack Papciak 2F » Sun Jan 21, 2018 9:09 pm

What is a simple definition for work? I keep getting it confused with heat

Emily Duggan 1F
Posts: 42
Joined: Fri Sep 29, 2017 7:07 am

Re: work definition

Postby Emily Duggan 1F » Sun Jan 21, 2018 9:13 pm

work is the energy transferred by compression or expansion while heat is the energy transferred by heating or cooling. hope this helps!

Jacob Cho 2L
Posts: 12
Joined: Fri Sep 29, 2017 7:05 am

Re: work definition

Postby Jacob Cho 2L » Sun Jan 21, 2018 10:13 pm

Work is the measurement of energy required for any action, measured in Joules. Its definition is often represented by w = F * d which means work equals Force times distance; this reflects that work is also defined as force over any distance. Force, however, can come in many different forms. For example, and very important to us chemists, force equals pressure over an area (F = P * A), which means the work function defined earlier can be w = F * d = P * A * d. However, you might notice that when an area travels across a distance, like in the instance of a piston face going up/down a tube, A * d can is the same as A * h or volume. Thus, w = F * d = P * A * d = P * dV. Note, volume is delta volume because the measurement of distance that acts as height is actually the measurement of the difference in volume of the final from the initial. Other steps you can take to make this equation more versatile is to use the ideal gas law (P * V = n * R * T). This makes w = P * dV = dn * R * T. When looking at these equations, however, it is important to note which variables are changing and which are not. This will tell you under what conditions these equations may be used. For example, w = P * dV means constant pressure, changing volume; w = dn * R * T means constant temperature, changing moles.

Annalise Eder 2L
Posts: 49
Joined: Sat Jul 22, 2017 3:01 am

Re: work definition

Postby Annalise Eder 2L » Sun Jan 28, 2018 7:39 pm

Both have to do with a transfer of energy. Work is defined as the amount of energy transferred by a force acting through a distance. Heat is defined as the energy stored as random motion of molecules or atoms.

Ridhi Ravichandran 1E
Posts: 35
Joined: Sat Jul 22, 2017 3:01 am

Re: work definition

Postby Ridhi Ravichandran 1E » Sun Jan 28, 2018 10:20 pm

Work is defined as motion against an opposing force. In Chapter 8, we focus on expansion work, such as a gas expanding against a piston. The piston provides an opposing force. If it weren't there (if the gas was expanding into a vacuum, for example), no work would be done because there would be no opposing force.

There is also non-expansion work, such as raising an object off the ground against the force of gravity. However, we are not focusing on this type of work.

Also, it is important to remember that work is NOT a state function, so it matters how the work is done.

Michelle Steinberg2J
Posts: 73
Joined: Fri Sep 29, 2017 7:04 am

Re: work definition

Postby Michelle Steinberg2J » Tue Jan 30, 2018 3:01 pm

I also get confused between differentiating work and heat, so I understand!
This is how I think about it:
Work and heat are both forms of energy. The difference is how that energy is being transferred - it can be transferred with heat or with work. Heat is a form of energy transferred due to a difference in temperature . This is a result of the collision of fast/slow molecules. Thus, when a hot piece of copper is put into a cup of water, the heat from the copper will flow into the water. You can see here that no work is being done. Only heat. Work, however, is when you achieve motion against an opposing force - ergo expansion or compression. Work has a direction.

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