Mistakes, errors, uncertainties Flashcards
Error
The difference between the value found in an experiment and the ‘actual’/correct value
Systematic error
Caused by apparatus
Random error
Caused by unpredictable conditions or by a difference in recording that is hard to get rid of
Precision
How close the values are to each other
Good precision = concordant results
Accuracy
How close the value from the experiment is close to the correct value
Mistake
Caused by the fault of the experimenter which can be avoided if they are cautious
How to reduce random errors?
Repeat experiment multiple times
Can repeating experiment with same apparatus reduce systematic errors?
No because these are caused by apparatus so the flaws in this apparatus will still affect the repeated measurements
Measurement uncertainty
Potential error possible when taking a reading from an apparatus
The number that is +/- a value
How is the measurement uncertainty derived from?
The precision of the balance so plus or minus the smallest scale division
Divide by 2
How to decrease the measurement uncertainty of apparatus?
Use one that is of higher greater precision so with a smaller scale division
What is the total uncertainty of a burette?
2 times the smallest scale division (divided by 2) because you read it twice = once for initial reading and move for final reading
How to work out the percentage measurement uncertainty?
uncertainty x number of times apparatus is read
——————————————
Measurement taken
Multiply by 100
Percentage uncertainty for a burette
Uncertainty of burette
———————————
Titre volume taken
Multiply by 2 because burette is read twice
Multiply by 100
Percentage uncertainty for volumetric flask (used to make up standard solution)
Uncertainty
——————
Volume of flask
Multiply by 100
