q and temp increase


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Emily Glaser 1F
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Joined: Thu Jul 27, 2017 3:01 am

q and temp increase

Postby Emily Glaser 1F » Mon Feb 12, 2018 3:47 pm

If the q of a reaction is negative, does that mean that the temperature is decreasing.

If delta U is negative, does that indicate a temperature decrease

Lauren Seidl 1D
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

Re: q and temp increase

Postby Lauren Seidl 1D » Mon Feb 12, 2018 3:57 pm

Because q=n*C*deltaT, and neither moles nor molar heat capacity can be negative, a negative q would mean that delta T is negative. So yes, a negative q means that temperature is decreasing. A negative deltaU does not necessarily mean temperature is decreasing because deltaU=q+w. So even if q was positive (meaning an increase in temperature), the value of work could be negative enough to make deltaU a negative value.

Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

Re: q and temp increase

Postby siannehazel1B » Mon Feb 12, 2018 4:04 pm

a negative q does not necessarily mean that the temperature will decrease as shown by the heat curve: The diagonal lines indicate an increase/decrease in temperature as a result of the change in energy, the flat parts of the graph show that energy is being added/removed however the temperature does not change (hence the flat line).

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