# Chemistry lab uncertainty help?

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I'm doing an experiment and have these values:

Initial temperature: 21.0°C ± 0.5°C

Final temperature:

63.0°C ± 0.5°C (1st trial)

60.0°C ± 0.5°C (2nd trial)

So the average change in temperature is 40.5°C. Now I need help with my uncertainties. I'm not sure how to find it out. Do I just add all the uncertainties and get ± 2? Please help me

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Carry out your uncertainty calculations as you would normally. Remember when summing or subtracting unit values, the uncertainties add.

first value: (63.0°C ± 0.5)-(21.0°C ± 0.5)= 42.0± 1.0

second value (60.0°C ± 0.5)-(21.0°C ± 0.5)= 39.0± 1.0

You know the average is the sum of the first and second values divided by 2. When dividing non-unit values, you simply divide the uncertainty with the averaged value. Don't get this confused when you must add the percentage uncertainties for values with units.

average value:

=[(42.0± 1.0)+(39.0± 1.0)]/2

=(81.0± 2.0)/2

=40.5±1.0

Sorry for not throwing the Celsius units in there.

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Posted · Hidden by CkyBlue, April 11, 2012 - thank you post
Hidden by CkyBlue, April 11, 2012 - thank you post

Oh was it really that easy? Haha thanks a lot! I actually WAS looking at percentage uncertainties but didn't quite know how to use them. Well this is quite straight forward.

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