I am helping my daughter do her chemistry homework and am stumped by this one. I have a beaker that seems to count by 50s.

That makes uncertainty calculations awkward. What is the “next unit down”?

How should one calculate uncertainty for this?

enter image description here

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    $\begingroup$ Vaccano, No need to feel bad! Chemistry teachers should stop asking these questions, especially the uncertainty by arbitrary rules. It is pure non-sense. The reason is that there is no true answer to such questions. What you can do is that you can mentally draw 5 divisions or 10 divisions between the two marks (corresponding to 50 mL). Estimate the volume. Since there are 50 mL graduations, the so-called uncertainty would be 50 mL/5= +/-10 mL. Some would suggest to divide 50 mL/10 =+/-5 mL uncertainty. The volume is more than 125 mL but not 140 mL. Estimate the value mentally or on paper. $\endgroup$
    – AChem
    Sep 5, 2023 at 2:29
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    $\begingroup$ This video might be helpful youtube.com/watch?app=desktop&v=BkBZn794kSA $\endgroup$
    – AChem
    Sep 5, 2023 at 2:31
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    $\begingroup$ There are three independent but related things: Resolution, precision and accuracy. $\endgroup$
    – Poutnik
    Sep 5, 2023 at 9:41

1 Answer 1


A real beaker says "approximate volume".

enter image description here

So the volume is approximately between 100 mL and 150 mL. So maybe 125 mL with an uncertainty of 25 mL. Your daughter would know best because she could apply exactly the rules she learned in class.

There is no universally accepted answer because the beaker is not made to measure volume accurately.


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