8.1 question

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Wilson Yeh 1L
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8.1 question

Postby Wilson Yeh 1L » Wed Jan 17, 2018 9:04 pm

Why is coffee in a thermos bottle considered an isolated system? Why is it not closed? From personal experience the coffee in my thermos bottles would eventually cool down within an hour or so--doesn't that mean energy is being exchanged with the surroundings?

Lena Nguyen 2H
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Re: 8.1 question

Postby Lena Nguyen 2H » Wed Jan 17, 2018 9:14 pm

Thermos bottles are supposed to be insulated to prevent heat from escaping. The book mentions that thermos bottles are isolated systems on p. 260.

Matthew Lin 2C
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Re: 8.1 question

Postby Matthew Lin 2C » Wed Jan 17, 2018 9:16 pm

The question calls it a "very high quality" thermos bottle, so I think that it wants you to assume that the coffee is perfectly insulated. Therefore, no heat would be transferred in or out, making it an isolated system. Hope this helps!

Essly Mendoza 1J
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Re: 8.1 question

Postby Essly Mendoza 1J » Thu Jan 18, 2018 4:24 pm

Could anyone clarify why a bomb calorimeter in which benzene is burned considered an isolated system? Thank you!

Nicole Anisgard Parra 2H
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Re: 8.1 question

Postby Nicole Anisgard Parra 2H » Thu Jan 18, 2018 4:54 pm

A bomb calorimeter would be considered an isolated system because the system is closed off to the external environment, being incased within the exterior, insulating walls. Therefore, there is no transfer of heat to the outside surroundings; thus, it is an isolated system.

Amy Zheng 2l
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Re: 8.1 question

Postby Amy Zheng 2l » Thu Jan 18, 2018 10:19 pm

Insulation usually means isolated

Humza_Khan_2J
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Re: 8.1 question

Postby Humza_Khan_2J » Fri Jan 19, 2018 10:16 am

Furthermore, in all of these examples, matter cannot escape either. Both matter and heat must be trapped within the system for it to be isolated.

Brenda K 1J
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Re: 8.1 question

Postby Brenda K 1J » Fri Jan 19, 2018 10:47 am

In reality, we know that over time, heat will be lost in a thermos bottle, so it practically a closed system. In theory, however, an insulated thermos bottle is an isolated system because neither mass nor energy is exchanged with its surroundings.

LMendoza 2I
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Re: 8.1 question

Postby LMendoza 2I » Fri Jan 19, 2018 11:11 am

Coffee in a thermos bottle would not exchange heat with it's surroundings because a thermos bottle is an isolated system. Therefore, it cannot exchange energy or matter with it's surroundings. However, the amount of time the temperature of the coffee remains hot can really depend on the type of thermos bottle you are using.


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