Sign of Energy Density

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Rebecca Remple 1C
Posts: 137
Joined: Wed Sep 18, 2019 12:16 am
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Sign of Energy Density

Postby Rebecca Remple 1C » Sun Feb 09, 2020 6:00 pm

Hi all,

In homework problem 4D.9 we are asked to calculate the energy density of a reaction. I found the enthalpy, which was negative. This meant that energy/heat was being released. However, according to the solutions manual, the sign changed to positive when calculating the energy density of the reaction. I'm not sure why this is. Is energy density always positive, or was there a key word/phrase that was supposed to indicate a sign change. Please share your thoughts. Thank you!

-Rebecca Remple

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Sign of Energy Density

Postby Alice Chang 2H » Sun Feb 09, 2020 6:27 pm

I think energy density is always positive, since the definition of energy density is "the amount of energy stored in a given system or region of space per unit volume."

I don't think energy can be negative (but I may be wrong), so energy density can't be negative.

Rebecca Remple 1C
Posts: 137
Joined: Wed Sep 18, 2019 12:16 am
Been upvoted: 1 time

Re: Sign of Energy Density

Postby Rebecca Remple 1C » Mon Feb 10, 2020 5:00 pm

Alice Chang 2H wrote:I think energy density is always positive, since the definition of energy density is "the amount of energy stored in a given system or region of space per unit volume."

I don't think energy can be negative (but I may be wrong), so energy density can't be negative.

Hi Alice,

Thank you so much for your help! I reviewed the concept and your explanation makes a lot of sense. Good luck on the midterm :)

-Rebecca


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