1. Unit 1 Types of Errors

2.  Operator Ability – Differences in skill or attention to detail can lead to dramatically different results between different people.  Practice the techniques to improve accuracy.  a.k.a. User Error.

3. 2) Measuring Device:  A) Calibration (Scale of device) – Using a measuring device that is to coarse or too fine  Can introduce errors due to estimation or compounding measurements.  Use the appropriate tool in order to reduce errors.

4.  B) Bias of measuring device – Error that is reproducible and predictable. Alter by manipulating data.  Correct bias by adding, subtracting, multiplying, or dividing by a correction factor.  a.k.a. Systematic error.  e.g. If a scale routinely measures 0.015 g more than the actual amount, subtract 0.015 g from all of your measurements to “zero in” on the correct value – this must be explained in the reporting of your results.

5. 3) Random Error – Error that cannot be predicted, reproduced, or otherwise accounted for.  Spillage is by far the most common form of random error.  Be careful with procedure to reduce this type of error.

6. #Error DescriptionType of Error 1 A dirty stirring rod introduces a contaminant into the reaction which increases the apparent result by 2% 2 One lab partner reads the mass to be 5.873 g while the other lab partner reads the mass to be 5.9 g 3 A procedure calls for 5.0 mL of HCl to be added to the reaction. A 100 mL beaker is used to measure the 5 mL.

7. 4 When drying, a small pocket of water is trapped in the crystals and adds an additional 5% to the mass. 5 A technique routinely measures the density of known substances 1.28% higher than expected. 6 A student records a length to be 4.25 cm but does not align the ruler with the very tip of the object. 7 A procedure calls for 250 mL of water. A student uses a 25 mL graduated cylinder, filling it 10 times.

8. 8 A solution is boiled rapidly to dry the product. No lid is used on the beaker. After the experiment, little white dots can be seen on the lab bench. 9 Two students collide in the lab while one of the students is carrying her product. A small amount spills out of the container unnoticed. 10 A filter paper rips slightly and some residue leaks into the filtrate.