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When to use + sign

Posted: Sat Feb 10, 2018 1:19 pm
by MSkye Goldwater 2K
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?

Re: When to use + sign

Posted: Sat Feb 10, 2018 1:39 pm
by Joyce Lee 1C
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.

Re: When to use + sign

Posted: Sat Feb 10, 2018 2:58 pm
by Alvin Tran 2E
It's good notation for whenever you're dealing with change in a value.

Re: When to use + sign

Posted: Sat Feb 10, 2018 3:04 pm
by Justin Folk 3I
So since it's for a change its always used?

Re: When to use + sign

Posted: Sat Feb 10, 2018 3:11 pm
by Alvin Tran 2E
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.

Re: When to use + sign

Posted: Sat Feb 10, 2018 4:08 pm
by RussellChin_3A
Using + just makes it more identifiable that a system is gaining something. Its more clear than just leaving a number without a +

Re: When to use + sign

Posted: Sat Feb 10, 2018 4:12 pm
by Ashley Macabasco 2K
You should always use a + or - sign when doing change calculations to determine whether something is being lost or gained through a reaction.

Re: When to use + sign

Posted: Sat Feb 10, 2018 4:53 pm
by Scott Chin_1E
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.

Re: When to use + sign

Posted: Sat Feb 10, 2018 5:23 pm
by Abigail Urbina 1K
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.

Re: When to use + sign

Posted: Sat Feb 10, 2018 6:02 pm
by Kellina Tran 2I
I think even if the solution should manual doesn’t always use the + sign, it would be preferable to use it for tests/exams

Re: When to use + sign

Posted: Sat Feb 10, 2018 7:51 pm
by 204918982
So should we always put a + sign on positive answers for change calculations on tests/exams?

Re: When to use + sign

Posted: Mon Feb 12, 2018 4:13 pm
by Alex Nechaev 1I
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.