how serious are sig figs

[Nato]

hi

we are learning the mole concept at school (units 1/2) and i was wondering how serious it is to be really precise with sig fig.
for example if the the answer is 1.81 x 10^5 i usually get something like 1.82 x 10^5. is this in anyway acceptable
on test and exams and especially for year 12.

thank you

[Limista]

hi

we are learning the mole concept at school (units 1/2) and i was wondering how serious it is to be really precise with sig fig.
for example if the the answer is 1.81 x 10^5 i usually get something like 1.82 x 10^5. is this in anyway acceptable
on test and exams and especially for year 12.

thank you

This happens to me sometimes to. I think the answer to your question is: it depends.

* if you've used the entire value in you calculator, and you don't round off when you type in numbers, then your answer is definitely correct

* stick to using the periodic table printed by VCAA when doing the molar masses - this is the one you'll use in the exam anyways

[Ancora_Imparo]

The way VCE works is that they only check that you have the correct number of significant figures for one question in the paper. The catch is, they don't tell you which one! So, you have to be careful for every question.

Say a volumetric analysis question involving multiple calculations. Ie: You get a question with parts a. to e.
Within each part of the question, always keep using the numbers on your calculator memory. Do NOT round at any stage within a part of question on your calculator. However, when writing down steps, it's good to show numbers to the correct number of significant figures so that when you reach the end of that part and have to state your answer, you can easily determine how many sig figs it's going to be.

If you have to use your answer from part a. in part b., for example, you then use the rounded answer that you wrote down, not the one on your calculator. You then proceed as above.

If you get into these habits early, you'll be fine in SACs and the exam!