In a chemistry question, I was given a temperature 19 degrees C, which I converted into 292K for the calculation. When I come to give my answer, should I give it to two significant figures (since only two were given in the question for temp.) or three (as the temp is to three sig fig when converted to kelvin)?
Many thanks in advance
Many thanks in advance
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You have to treat temperature readings different from most other numbers as they have an offset zero. That is, percentage error or percentage of reading is totally meaningless. And stating number of significant digits is an indirect way of listing a percent error.
You won't find a temperature reading device with an accuracy specification of 1% of reading, for example, but rather as a ± a number of degrees. Reason should be obvious, but consider a temperature reading of 1ºC ±1% as compared to a 34ºF ±1%. Same temperature, much different errors.
And stating number of significant digits is an indirect way of listing a percent error.
So you use the number of degrees as the uncertainty. 19ºC is an uncertainty of ± 0.5 ºC. And when your conversion is done, it should still be the same uncertainty.
You won't find a temperature reading device with an accuracy specification of 1% of reading, for example, but rather as a ± a number of degrees. Reason should be obvious, but consider a temperature reading of 1ºC ±1% as compared to a 34ºF ±1%. Same temperature, much different errors.
And stating number of significant digits is an indirect way of listing a percent error.
So you use the number of degrees as the uncertainty. 19ºC is an uncertainty of ± 0.5 ºC. And when your conversion is done, it should still be the same uncertainty.
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i don't think the significant figures concept is applicable when all your numbers are integers - it would be if some had decimal points or not - if the toss-up is between 292 and (290?) the more exact is always preferable