Absorb means "+"?

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Absorb means "+"?

Postby 205192823 » Mon Mar 02, 2020 6:08 pm

In a combustion chamber, the total internal energy change produced from the burning of a fuel is -2573 kJ. The cooling system that surrounds the chamber absorbs 947 kJ as heat. How much work can be done by the fuel in the chamber? [CH 4B #7] I was a little confused with this problem because I thought if something was being absorbed it was a + value. I understand that delta U = -2573 and I thought q= + 947 and the equation to figure out w is w=delta U - q, but inputting my values I got the wrong answer and having a -q value gave me the right answer, so does absorb not mean its a positive q value?

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Re: Absorb means "+"?

Postby alicechien_4F » Mon Mar 02, 2020 10:13 pm

I think it is -q because it is the cooling system around the chamber, rather than the chamber itself that is absorbing the heat. This means the chamber is releasing heat.

Jaklin Astvatsatryan
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Re: Absorb means "+"?

Postby Jaklin Astvatsatryan » Mon Mar 09, 2020 9:19 am

q would be a negative value because it is the cooling system around the chamber. The chamber is releasing heat into the surrounding.

Asha Agarwal 1E
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Re: Absorb means "+"?

Postby Asha Agarwal 1E » Mon Mar 09, 2020 10:41 am

While the outside system is absorbing the heat (+q, you are looking at the system itself, not the surroundings meaning the heat released
into the system is -q of the surroundings.

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Re: Absorb means "+"?

Postby BCaballero_4F » Mon Mar 09, 2020 10:10 pm

The chamber itself is releasing heat, not absorbing, giving a -q

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