[DannyBoi]

Hi,

I've been trying to get a straight answer but the internet and my online chem exercises seem to go about solving problems a different way. Online I have found people say to not round your answers to the sig fig until your last step (the solution). In other words, it's fine to keep extra figures in intermediate steps. But then the online part of my textbook has a problem where on the first step they round the answer they get:

q = (4.184 J/g*K)(1000.g)(80. K) = 330,000 J

My calculator tells me 334,720 J, so why would they round at such an early step? Wouldn't that introduce rounding errors? Any clarification on this is appreciated.

[MrTeo]

From my personal experience I know that all the figures should be taken into consideration in intermediate steps (it's a good habit to save them on your calculator and not to copy them on a sheet, as you'll lose a significant amount of precision). In addition to that the book also shows the result with the wrong number of sig figs (the right number, with the values written like that is 4, not 6)...

More info here:
http://en.wikipedia.org/wiki/Significant_figures
http://en.wikipedia.org/wiki/Significance_arithmetic

[Borek]

I think you may be mistaking two things here. When you do the calculations, you don't round down intermediate results, but if you report them (for any reason), you should report them correctly.

Don't pay too much attention to sig figs, they are rarely used in the real world.

[DannyBoi]

Ok so I'm not allowed to report the intermediate steps with more sig figs than are allowed. In other words I have to keep track of the actual longer answers seperately.

[DannyBoi]

What I mean to ask is: Will I lose marks on an exam if my intermediate steps carry with them 1-3 more sig figs than given in the problem? Or will I be ok as long as my final solution keeps the correct number of sig figs?

[Borek]

Are you reporting them (as in a multistep calculation, where results from earlier steps are necessary in later ones), or just writing down for your convenience?

Note that a lot may depend on the grading person, some treat sig figs deadly serious. You better ask before the exam, so that you know what you are expected to do.