Meaning of q=-w


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Chloe Alviz 1E
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Meaning of q=-w

Postby Chloe Alviz 1E » Tue Feb 11, 2020 3:26 pm

I know when ΔU = 0, but in these cases, how do I interpret q=-w?

Sebastian Lee 1L
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Re: Meaning of q=-w

Postby Sebastian Lee 1L » Tue Feb 11, 2020 3:45 pm

Knowing that q=-w when the change in internal energy is 0 just helps you solve problems that may require work (but you're only given heat) or vice versa. You know that the work done by a system expanding isothermally is the opposite sign of the heat coming into the system. Note that the internal energy for an ideal gas will always be 0 if the temperature doesn't change (isothermal).

Jainam Shah 4I
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Re: Meaning of q=-w

Postby Jainam Shah 4I » Tue Feb 11, 2020 11:05 pm

When q=-w that means that internal energy is zero which typically is seen in isothermal reversible expansion.

Gurmukhi Bevli 4G
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Re: Meaning of q=-w

Postby Gurmukhi Bevli 4G » Fri Feb 14, 2020 10:09 pm

q=-w when the internal energy of a system is 0, (normally q=U-w). This happens when an isothermal reversible expansion is taking place since work is being done by the system (and heat is leaving the system).

Matthew Tsai 2H
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Re: Meaning of q=-w

Postby Matthew Tsai 2H » Sat Feb 15, 2020 11:53 am

When the change in internal energy is zero, it means that all the heat added to the system must be used by the system to do work.

Jacob Motawakel
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Re: Meaning of q=-w

Postby Jacob Motawakel » Sat Feb 15, 2020 3:08 pm

When q=-w, internal energy is equal to 0, which indicates constant temperature.

Nuoya Jiang
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Re: Meaning of q=-w

Postby Nuoya Jiang » Sat Feb 15, 2020 3:51 pm

Usually, in an isothermally reversible gas expansion, the work done by the heat equals the heat it received.

Betania Hernandez 2E
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Re: Meaning of q=-w

Postby Betania Hernandez 2E » Sun Feb 16, 2020 5:25 pm

q=-w can help you figure out that the reaction is isothermal reversible which means that it has a constant temperature and that the internal energy equals zero.

J_CHEN 4I
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Re: Meaning of q=-w

Postby J_CHEN 4I » Sun Feb 16, 2020 6:22 pm

The heat supplied to the system is equivalent to the energy leaving the system as work.

Areli C 1L
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Re: Meaning of q=-w

Postby Areli C 1L » Sun Feb 16, 2020 8:00 pm

This usually means that its an isothermal reversible reaction and that the internal energy is 0.
Id also suggest watching the Organic chemistry tutor on youtube as he has videos on thermodynamics!

KHowe_1D
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Re: Meaning of q=-w

Postby KHowe_1D » Sun Feb 16, 2020 8:04 pm

When delta U is zero that means the equation deltaU = q+w is now 0=q+w so you can now change the equation to be q=-w

w is negative because you can have negative work but you can't have negative heat energy. It essentially just means that the heat added to the system is the same as the work being done by the system.

TimVintsDis4L
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Re: Meaning of q=-w

Postby TimVintsDis4L » Sun Feb 16, 2020 8:25 pm

If the Internal Energy of the System is equal to 0, then q must = - w so that they cancel out and you're left with 0.

Mai V 4L
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Re: Meaning of q=-w

Postby Mai V 4L » Mon Mar 09, 2020 2:24 pm

Can q be constant in this case?

William Chan 1D
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Re: Meaning of q=-w

Postby William Chan 1D » Wed Mar 11, 2020 10:32 pm

Basically, if the change in energy of the system is 0, then that means no energy is lost or gained in the system. That means that any heat is used to do work or vice versa.

Bryan Chen 1H
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Re: Meaning of q=-w

Postby Bryan Chen 1H » Wed Mar 11, 2020 10:41 pm

isothermal reversible expansion


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