sig figs

Moderators: Chem_Mod, Chem_Admin

connie 2C
Posts: 106
Joined: Thu Jul 11, 2019 12:17 am

sig figs

Postby connie 2C » Fri Oct 04, 2019 2:50 pm

can someone explain when to round off when using sig figs?

Kehlin Hayes 4C
Posts: 50
Joined: Wed Sep 18, 2019 12:17 am

Re: sig figs

Postby Kehlin Hayes 4C » Fri Oct 04, 2019 2:59 pm

The best measure of how many sig figs to use is to look in the question provided and use the smallest amount, it also helps to try and keep the number of sig figs consistent for all measurements.

Emily_4B
Posts: 57
Joined: Wed Sep 18, 2019 12:21 am

Re: sig figs

Postby Emily_4B » Fri Oct 04, 2019 4:13 pm

Yes as the previous post mentioned you want to round off your number of significant figures to the same amount of sig figs that the question has :)

jeffreygong1I
Posts: 49
Joined: Thu Jul 11, 2019 12:15 am

Re: sig figs

Postby jeffreygong1I » Sat Oct 05, 2019 10:37 pm

You should round off only at the very end and keep everything in the intermediate calculations(or keep, like, 2 extra decimal places, I guess).

Kimme Chun 1I
Posts: 22
Joined: Sat Sep 07, 2019 12:17 am
Been upvoted: 1 time

Re: sig figs

Postby Kimme Chun 1I » Sun Oct 06, 2019 3:11 pm

How do I tell what 0's are significant and which aren't?

gferg21
Posts: 51
Joined: Sat Aug 17, 2019 12:17 am

Re: sig figs

Postby gferg21 » Sun Oct 06, 2019 3:53 pm

If there are zeros before the sig figs (like 0.0001), then all of the zeros are significant. If the number is an integer like 10, the zero is significant because there are no decimals. If it were 10.0, the last zero would not be considered to be significant unless specified by the question. If the number was like 0.100, neither of the zeros after the one would be significant.

Lauren Bui 1E
Posts: 54
Joined: Sat Jul 20, 2019 12:15 am

Re: sig figs

Postby Lauren Bui 1E » Sun Oct 06, 2019 5:32 pm

you should use exact values from the periodic table and avoid rounding or using sig figs until the very end. this will minimize rounding error :)

Rebekah Alfred 1J
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am
Been upvoted: 1 time

Re: sig figs

Postby Rebekah Alfred 1J » Sun Oct 06, 2019 5:44 pm

How do I tell what 0's are significant and which aren't?

If you want to practice determining how many significant figures a number has, this could be helpful:
https://www.khanacademy.org/math/arithmetic-home/arith-review-decimals/arithmetic-significant-figures-tutorial/e/significant_figures_1

Joanna Mendoza 3J
Posts: 20
Joined: Sat Aug 24, 2019 12:17 am

Re: sig figs

Postby Joanna Mendoza 3J » Sun Oct 06, 2019 6:09 pm

Some rules for significant figures: non zero numbers are always significant, any zero between 2 non zero numbers are significant, and trailing zeros after a decimal point are significant.

Jasmine Kim 1L
Posts: 71
Joined: Fri Aug 02, 2019 12:16 am

Re: sig figs

Postby Jasmine Kim 1L » Mon Oct 07, 2019 12:23 am

This is what I got from Appendix 1 (1C) in the textbook:
-Addition and Subtraction: round to the lowest number of sig figs after the decimal
-Multiplication and Division: round to the lowest number of sig figs in general

-Zeros between nonzero numbers (ex. 30.1): significant
-Zeros after the decimal (ex. 3.0): significant because they are measured
-Zeros before sig figs that are less than 1 (ex. 0.005): insignificant because they are just placeholders.
-Zeros after a whole number (ex. 100): ambiguous, can be considered as having only 1 sig fig unless there is a decimal (100. has 3 sig figs) or there is scientific notation (1.00 x 10^2 has 3 sig figs).

Maya Serota 3G
Posts: 53
Joined: Tue Sep 24, 2019 12:17 am

Re: sig figs

Postby Maya Serota 3G » Mon Oct 07, 2019 8:37 am

After reading these posts I am confused about whether or not a zero is considered a sig fig if there is a number like 13.0
Since the zero is trailing the decimal point would it or would it not be a sig fig when doing arithmetic calculations?

Maya Serota 3G
Posts: 53
Joined: Tue Sep 24, 2019 12:17 am

Re: sig figs

Postby Maya Serota 3G » Mon Oct 07, 2019 8:47 am

Will we be marked down on an exam for using the incorrect amount of sig figs in our answer?

Paul Hage 2G
Posts: 105
Joined: Thu Jul 25, 2019 12:17 am

Re: sig figs

Postby Paul Hage 2G » Mon Oct 07, 2019 11:24 am

Maya Serota 3G wrote:After reading these posts I am confused about whether or not a zero is considered a sig fig if there is a number like 13.0
Since the zero is trailing the decimal point would it or would it not be a sig fig when doing arithmetic calculations?


In the example you gave (13.0), the 0 would be considered a sig fig when doing arithmetic calculations because it comes after the decimal point.

Mitchell Koss 4G
Posts: 128
Joined: Sat Jul 20, 2019 12:17 am

Re: sig figs

Postby Mitchell Koss 4G » Tue Oct 08, 2019 2:58 pm

Also, do not worry too much as sig figs are not vital to test 1. Try your best but sig figs do not need to be absolutely mastered to score well on test 1

Mitchell Koss 4G
Posts: 128
Joined: Sat Jul 20, 2019 12:17 am

Re: sig figs

Postby Mitchell Koss 4G » Tue Oct 08, 2019 2:59 pm

13.0=3 sig figs
13=2 sig figs
13000=2 sig figs
13000.=5 sig figs

Victoria Otuya 4F
Posts: 50
Joined: Wed Sep 18, 2019 12:21 am

Re: sig figs

Postby Victoria Otuya 4F » Wed Oct 09, 2019 12:53 am

Zeros are not considered a sig fig if it is in front of a decimal. For example, 0.245. Since the zero is in front of the decimal, it would not be counted as a sig fig. So in response the sig fig would be three. If it is still confusing, the link below explains it better than I do.

https://youtu.be/IIQPHC5gZT8

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

Re: sig figs

Postby Chem_Mod » Wed Oct 09, 2019 9:44 am

Kehlin Hayes 4C wrote:The best measure of how many sig figs to use is to look in the question provided and use the smallest amount, it also helps to try and keep the number of sig figs consistent for all measurements.


This is generally a great practice, however, there are slightly different sig fig rules for addition/subtraction versus multiplication/division.

Check out page 6 and 7 of this link for more info http://tournas.rice.edu/website/documen ... Rules1.pdf

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

Re: sig figs

Postby Chem_Mod » Wed Oct 09, 2019 9:47 am

Kimme Chun 1I wrote:How do I tell what 0's are significant and which aren't?


Here's a link with a good trick for remembering which 0's are significant. https://www.kentchemistry.com/links/Mea ... igfigs.htm

Robin Cadd 1D
Posts: 113
Joined: Thu Jul 11, 2019 12:16 am

Re: sig figs

Postby Robin Cadd 1D » Wed Oct 09, 2019 11:22 am

Adding/Subtracting --> round to the least precise # (i.e. 4.23+4.542 = ? ; Your answer should have 2 decimal points)
v.
Mutiplying/Dividing --> # of sig figs in answer = least # of sig figs in whatever you're multiplying (i.e. 4.0*2 =8)

rachel liu 3k
Posts: 56
Joined: Sat Aug 17, 2019 12:16 am

Re: sig figs

Postby rachel liu 3k » Thu Oct 10, 2019 6:51 pm

Does anyone know if points will be taken off due to sig figs? My high school chem teacher was super specific on SFs.

Tiffany Chao 2H
Posts: 117
Joined: Fri Aug 09, 2019 12:17 am

Re: sig figs

Postby Tiffany Chao 2H » Thu Oct 10, 2019 7:19 pm

When doing the actual work for the problem, don't round off and try to keep intermediate answers 3-4 decimal places. However, at the very end, you want to round off based on the lowest number of sig figs. If you don't know the rules for sig figs, I'd suggest you to look at Professor Lavelle's website link called, "Everything you want to know about Sig Fig"


Return to “Accuracy, Precision, Mole, Other Definitions”

Who is online

Users browsing this forum: No registered users and 0 guests