## q and w

Lauryn Jordan 1F
Posts: 76
Joined: Fri Sep 29, 2017 7:07 am

### q and w

can someone clarify what q and w are as well as how can you tell if they will be positive or negative?

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

### Re: q and w

Hey,
W is work and Q is heat. Work is motion against an opposing force, and heat is the energy transferred as a result of a temperature difference. When work is done on a system, w is positive, and when work is done by the system, w is negative. If heat enters the system, q is positive, and if heat leaves the system, q is negative.

Lauryn Jordan 1F
Posts: 76
Joined: Fri Sep 29, 2017 7:07 am

### Re: q and w

soooo my follow up question would be when do you know when work is done on a system vs done by a system?

Kristin Ishaya 1A
Posts: 30
Joined: Fri Sep 29, 2017 7:04 am

### Re: q and w

As defined by the textbook, “q is the energy supplied to the system as heat and w is the energy supplied the system as work” (page 278). Basically, q refers to the energy that is transferred or absorbed in a system and work is caused by either an internal or external force that is applied to the system.

Anh Nguyen 2A
Posts: 36
Joined: Fri Sep 29, 2017 7:05 am
Been upvoted: 1 time

### Re: q and w

q is the energy transferred by heat.
w is the energy transferred by doing work.
If heat has flowed from the system then q is negative. If the system absorbs heat then q is positive.
And for w, if work is done on the system then w is positive, like compressing gas inside an insulated container increases its internal energy. If work is done by the system then w is negative (gas expansion).

Jonathan Tangonan 1E
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

### Re: q and w

Overall, q and w added together make up the internal energy that happens within a system. Q is the energy transferred as heat where a positive q would indicate an absorption of heat while a negative q would indicate a release of heat from the system. A positive w would indicate that work has been done on a system whereas work done by a system would result in a negative w.