Sig figs

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Hannah_1G
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Sig figs

Postby Hannah_1G » Wed Oct 02, 2019 7:47 pm

For the homework are we supposed to be using a set significant figure number?

Haley Fredricks 1B
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Re: Sig figs

Postby Haley Fredricks 1B » Wed Oct 02, 2019 7:50 pm

No, you should be answering each individual question with the number of sig figs in the question (depending on addition or multiplication it could be different). There isn't a general set number of sig figs for the homework.

905416023
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Re: Sig figs

Postby 905416023 » Wed Oct 02, 2019 8:18 pm

it seems like for the most part many of the problems are only to 2 sig figs.

Hannah_1G
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Re: Sig figs

Postby Hannah_1G » Wed Oct 02, 2019 8:20 pm

If the question doesn't mention sig figs, should I not worry about the precision of the answer then?

AndreiRekesh1I
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Re: Sig figs

Postby AndreiRekesh1I » Wed Oct 02, 2019 8:22 pm

It's probably best to use the number of sig figs in the givens.

Michelle Shin 4B
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Re: Sig figs

Postby Michelle Shin 4B » Wed Oct 02, 2019 8:41 pm

For sig figs make sure to use the smallest value of sig figs in the given (ex. 4.00 is 3 sig figs) and also use at the end of calculations.

905416023
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Re: Sig figs

Postby 905416023 » Wed Oct 02, 2019 9:03 pm

What if the question doesn't have numbers in it? Should I just do it to 3?

CynthiaLy4F
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Re: Sig figs

Postby CynthiaLy4F » Wed Oct 02, 2019 9:08 pm

No, the number of sig figs can vary because it is based on the least amount of sig figs present in the problem. However, any conversion factors do not count when determining the number of sig figs.

Jiyoon_Hwang_2I
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Re: Sig figs

Postby Jiyoon_Hwang_2I » Wed Oct 02, 2019 9:41 pm

You should always round your final answer to the correct number of sig figs. If you're doing addition/subtraction, round your answer to the least number of sig figs from any of the numbers in the given problem. If you're doing multiplication/division, round your answer to the least number of decimal places from the measurements given in the problem. Also, for determining whether or not a zero is significant, you should follow these two rules.

Sandwich rule: if a zero is between two significant figures, then the zero is also significant. (i.e. 304 --> the three and the four are significant so the zero in between is also significant)

Right-Right rule: if a zero is to the right of a significant figure and to the right of a decimal, then it is significant. (i.e. 9.0 --> the nine is significant and the zero is to the right of a decimal so it is significant)

Hannah_1G
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Re: Sig figs

Postby Hannah_1G » Wed Oct 02, 2019 9:45 pm

CynthiaLy3H wrote:No, the number of sig figs can vary because it is based on the least amount of sig figs present in the problem. However, any conversion factors do not count when determining the number of sig figs.

Thank you this helped a lot. I was looking for the homework question to mention how many sig figs to use, not how many they are giving in the given values.

205192823
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Re: Sig figs

Postby 205192823 » Wed Oct 02, 2019 9:49 pm

During discussion, my TA said that Professor Lavelle is more lenient about sig figs because students use to ask a lot of questions about that during lecture and would take too much time away. But you should still be aware of the values given in the questions and use those sig figs. That doesn't mean you should round up 0.677 to a 2 though.

805422680
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Re: Sig figs

Postby 805422680 » Wed Oct 02, 2019 9:58 pm

Sig figs should be designated individually for each problem. It's the least accurate out of all the numbers given. Also, make sure you don't round off digits when you're calculating. Only round off with sig figs at the end.

605110118
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Re: Sig figs

Postby 605110118 » Wed Oct 02, 2019 10:42 pm

How important is it to know all the rules for sig figs? I feel like I know some basics but not the more specific rules that pertain to addition/subtraction or multiplication/division?

Arianna Perea 3H
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Re: Sig figs

Postby Arianna Perea 3H » Wed Oct 02, 2019 10:49 pm

Do we apply Sig Figs after every calculation or only to the end result?

Reagan Smith 1H
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Re: Sig figs

Postby Reagan Smith 1H » Wed Oct 02, 2019 10:51 pm

I think you are supposed to do the sig figs only at the end so that your rounding doesn't get messed up but if you want to be super sure Dr. Lavelle has a Sig Fig review link on his 14A website
Last edited by Reagan Smith 1H on Wed Oct 02, 2019 11:13 pm, edited 1 time in total.

Julieta Serobyan4D
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Re: Sig figs

Postby Julieta Serobyan4D » Wed Oct 02, 2019 10:59 pm

Arianna Perea 3H wrote:Do we apply Sig Figs after every calculation or only to the end result?

I am not sure, but I usually do it at the end cause your result can be inaccurate, if you don't have enough sig.figs. I round up to 4 significant figures after each question and in the end round to the least sig.figs available in the problem.

Nicholas_Gladkov_2J
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Re: Sig figs

Postby Nicholas_Gladkov_2J » Wed Oct 02, 2019 11:06 pm

Julieta Serobyan4D wrote:
Arianna Perea 3H wrote:Do we apply Sig Figs after every calculation or only to the end result?

I am not sure, but I usually do it at the end cause your result can be inaccurate, if you don't have enough sig.figs. I round up to 4 significant figures after each question and in the end round to the least sig.figs available in the problem.


It's best if you round to the smallest number of sig figs at the end of the problem-- this will prevent any rounding error. Work through the problem as if sig figs never existed, then apply the rules of sig figs at the end. For multiplying just round to the smallest amount of sig figs (usually the amount of numbers there are).

chrischyu4a
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Re: Sig figs

Postby chrischyu4a » Fri Oct 04, 2019 4:50 pm

605110118 wrote:How important is it to know all the rules for sig figs? I feel like I know some basics but not the more specific rules that pertain to addition/subtraction or multiplication/division?


Back in high school, I know that sig figs account for a lot of points so I believe that it is important that you follow the rules for sig figs when notating your final answer. As for the rules, when mutiplying/dividing, you will need to have the same amount of sig figs as the value with the least amount of sig figs in your calculations
E.g. 5.51* 6.5=35.815 without sig figs, but since 6.5 has the least amount of sig figs compared to 5.51, your final answer will be 36 which has the same amount of sig figs as 6.5

When adding/subtracting, which you might not have to worry about as much as multiplying/dividing, you take the same amount of sig figs as the value in your calculations that has the least amount of digits to the right of the decimal.
e.g. 5.31-3.2= 2.11 without sig figs, but since 3.2 has the least amount of digits to the right of the decimal with 1 digit, your final answer will only have 1 digit to the right of the decimal which is 2.1

kpang_4H
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Re: Sig figs

Postby kpang_4H » Fri Oct 04, 2019 6:07 pm

https://lavelle.chem.ucla.edu/wp-conten ... OUT_SF.pdf
This is the link on Lavelle's website that explains how sig figs work. There is no set number of decimal places or sig fig for the whole set; after reading over the pdf, use sig figs at the end of your calculations to prevent a rounding error.


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