When to use + sign

MSkye Goldwater 2K
Posts: 19
Joined: Fri Sep 29, 2017 7:05 am

When to use + sign

I noticed in the solutions manual that sometimes a + sign is used for a positive change in something and sometimes it isn't. How do I know when to use it and when not to?

Joyce Lee 1C
Posts: 52
Joined: Fri Sep 29, 2017 7:03 am
Been upvoted: 1 time

Re: When to use + sign

I think generally using a + sign is just considered good notation. For example, if the answer's 9.12 J, it will often be written as +9.12 J.

Alvin Tran 2E
Posts: 39
Joined: Fri Sep 29, 2017 7:06 am

Re: When to use + sign

It's good notation for whenever you're dealing with change in a value.

Justin Folk 3I
Posts: 43
Joined: Wed Sep 21, 2016 2:56 pm

Re: When to use + sign

So since it's for a change its always used?

Alvin Tran 2E
Posts: 39
Joined: Fri Sep 29, 2017 7:06 am

Re: When to use + sign

On page 320 of the textbook it says, "A Note on Good Practice: Note the sign on the answer; always show the sign explicitly for the change in a quantity, even if it is positive." You wouldn't get marked wrong if you didn't have the positive sign though.

RussellChin_3A
Posts: 42
Joined: Sat Jul 22, 2017 3:01 am

Re: When to use + sign

Using + just makes it more identifiable that a system is gaining something. Its more clear than just leaving a number without a +

Ashley Macabasco 2K
Posts: 30
Joined: Fri Sep 29, 2017 7:05 am

Re: When to use + sign

You should always use a + or - sign when doing change calculations to determine whether something is being lost or gained through a reaction.

Scott Chin_1E
Posts: 55
Joined: Sat Jul 22, 2017 3:00 am

Re: When to use + sign

This would especially help when applying Le Chatelier's Principle as exothermic and endothermic reactions can shift the equilibrium of a system as well as in Electrochemistry where voltage of a battery should always be positive (it would be a good way to double check that you identified the correct cathode or anode). So as stated above, it would generally be very useful to use the (+) to indicate heat/energy loss or heat/energy gained so that it is more explicit.

Abigail Urbina 1K
Posts: 102
Joined: Thu Jul 27, 2017 3:01 am

Re: When to use + sign

Using a + or - sign in your calculations allows you to keep track of something that is either being gained or being lost, especially for problems that ask you to solve for any delta values.

Kellina Tran 2I
Posts: 50
Joined: Sat Jul 22, 2017 3:00 am

Re: When to use + sign

I think even if the solution should manual doesn’t always use the + sign, it would be preferable to use it for tests/exams

204918982
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: When to use + sign

So should we always put a + sign on positive answers for change calculations on tests/exams?

Alex Nechaev 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: When to use + sign

204918982 wrote:So should we always put a + sign on positive answers for change calculations on tests/exams?

I would say yes, since the examples we have done in class and the solutions in the manual all include the + sign for positive answers.

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