Accuracy and Precision

Abstract The purpose of this experiment is to become familiar with proper techniques for using the analytic balances, graduated cylinder, burette and pipette and determine which is more accurate and/or precise. In this experiment, the burette and pipette were more exact than the graduated cylinder and the analytic balance gave a very accurate and precise answer.

Results / Report

1) Weighing Copper Copper sample #: 1 Balance #: 14 Temperature: 22.8EC

Weighing Attempt #Mass of Copper Sample (g) 13.1234 23.1233 33.1235 43.1232

Average Mass = (3.1234g + 3.1233g + 3.1235g + 3.1232g) ÷ 4 =3.1234g

Standard Deviation

( - )( - ) 3.123400 3.1233- 3.1235 3.1232- Σ =

Or 0.0001

2) Burette Readings

a) Graduated Cylinder b) Pipette Initial Volume (mL)44.7244.91 Actual amount added (mL)Actual amount added (mL) 1st34.819.911st34.989.93 2nd24.909.912nd25.009.98 3rd15.059.853rd15.089.92

Graduated Cylinder average ( 9.91±0.01 mL + 9.91±0.01 mL + 9.85±0.01 mL ) ÷ 3 = 9.89±0.03 mL

Pipette average (9.93±0.01 mL + 9.98±0.01 mL + 9.92±0.01 mL) ÷ 3 = 9.94±0.03 mL

3)

Device Initial Mass (g)Final Mass (g)Resulting Water Mass (g) Graduated Cylinder21.529131.29879.7696 Pipette20.567430.49279.9253 Burette21.277931.326110.0482

TRUE VALUES Graduated Cylinder Density @ 24.3EC = 0.997225g/mL Volume = Mass ÷ Density = 9.7696g ÷ 0.997225g/mL = 9.7968 mL Pipette Density @ 23.3EC = 0.997470g/mL Volume = 9.9253g ÷ 0.997470g/mL = 9.9505 mL Burette Density @ 23.4EC = 0.997446g/mL Volume = 10.0482g ÷ 0.997446g/mL = 10.0739 mL

PERCENT ERROR Percent error = | true value – experimental value | x 100 true value

Graduated Cylinder % error = | 9.8mL – 10.0mL | x100 9.8mL = 2.04 % Pipette % error = | 9.95mL – 10.00mL | x100 9.95mL = 0.50 % Burette % error = | 10.07mL – 10.05mL | x100 10.07mL = 0.20%

4) Graduated Cylinder – lowest accuracy of the 3 instruments. The percentage error is 2.04% which is very high compared to the other

2. Pipette – middle accuracy of the 3 instruments. Its percentage error, 0.50% is good, but the burette is better. Burette – best accuracy of the 3 instruments. It has a low percentage error of 0.20%. When a very precise measurement is required, a burette is the best piece of equipment to use.

Conclusion By performing this experiment, we were able to determine which of the measuring devices were the most accurate and precise. The burette was shown to be the best choice for measuring the water. The analytical balance was shown to have accurate results as well, recording masses up to 4 decimal places. The thermometer used read to two decimal places which is accurate too.