Accuracy and Precision

AbstractThe 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 CopperCopper sample #: 1Balance #: 14Temperature: 22.8EC

Weighing Attempt #Mass of Copper Sample (g)13.123423.123333.123543.1232

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

Standard Deviation

( – )( – )3.1234003.1233-3.12353.1232-Σ =

Or 0.0001

2) Burette Readings

a) Graduated Cylinder b) Pipette Initial Volume (mL)44.7244.91Actual amount added (mL)Actual amount added (mL)1st34.819.911st34.989.932nd24.909.912nd25.009.983rd15.059.853rd15.089.92

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 Cylinder21.529131.29879.7696Pipette20.567430.49279.9253Burette21.277931.326110.0482

TRUE VALUESGraduated CylinderDensity @ 24.3EC = 0.997225g/mLVolume = Mass ÷ Density= 9.7696g ÷ 0.997225g/mL= 9.7968 mLPipetteDensity @ 23.3EC = 0.997470g/mLVolume = 9.9253g ÷ 0.997470g/mL= 9.9505 mLBuretteDensity @ 23.4EC = 0.997446g/mLVolume = 10.0482g ÷ 0.997446g/mL= 10.0739 mL

PERCENT ERRORPercent error = | true value – experimental value | x 100 true value

Graduated Cylinder% error = | 9.8mL – 10.0mL | x1009.8mL= 2.04 %Pipette% error = | 9.95mL – 10.00mL | x1009.95mL= 0.50 %Burette% error = | 10.07mL – 10.05mL | x10010.07mL= 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.

ConclusionBy 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.