Experiment #4
Weighing and Volumetric Techniques – 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.

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
=...

...Determining the accuracy of varieties of pipettes by weighing and finding the density of a liquid
Abstract
Different varieties of pipettes (P100, PR1000 pipettors and a serological pipette) along with a weighing balance was used in this investigation to check the density of an unknown liquid by first finding out what the liquid weighed and plotting a graph of the mass in grams against the volume of the liquid used in micro litres (µl) and finding the gradient of the graph (∆Y/∆X). Most of the standard deviation values were small showing that they were very close to the mean (average) hence more precise readings were obtained. The results from the graph also showed that the density of the unknown liquid A and B was denser that water and that is because it contains other dissolved substances which increased the overall weight.
Introduction
Pipetting requires a lot of skill to acquire precision and accuracy. For example the pipette tip must be pre-wet about three times before it is dipped into the solution [1] because dry and pre-wet pipette tips reveal greatest discrepancies. Dry pipette tips consistently deliver significantly lower volumes than did the pre-wet tips [2-6]. This can influence the readings showing on the balance as lower volumes will record lower mass and higher volume will record a higher mass which will in turn affect the density which will be measured making the results of the investigation incorrect. Using...

...measurements and data recording (significant
figures).
4. Become familiar with the errors, precision and accuracy associated the various measurement tools and techniques.
5. Determine the density of liquids and solids.
6. Determine the best-fit straight line as a method to examine linear relationships and to use this relationship as a
predicative model such as in the determination of the percent copper and zinc in pennies based on density
measurements.
7. Record laboratory data and observations.
MATERIALS:
Erlenmeyer Flasks
o 125 mL
o 250 mL
beakers
o 100 mL
graduated cylinders
o 10 mL
o 25mL
Burette
o 50 mL
Volumetric pipettes
o 10 mL
Measuring pipet
o 10 mL
Burette clamp and stand
Various liquids and solids for density determination measurements
o Liquids
Distilled water
Heptane
Carbon Tetrachloride
o Solids
Pennies
Copper
Zinc
Lead
Aluminum
BACKGROUND:
Laboratory glassware. There are two major categories of laboratory glassware:
(1) those that contain a certain volume (volumetric flasks) and
(2) those that deliver a certain volume (pipets, burets, and graduated cylinders).
“To Contain” glassware (sometimes labeled TC) is typically used for preparing solutions of known volume. “To
Deliver” glassware (sometimes labeled TD) is used to transfer known volumes between containers.
1
Some glassware is very carefully designed and marked for high accuracy/precision work (burets,...

...Precision describes the closeness of results that have been obtained in exactly the same way while accuracy indicates the closeness of the measurement to its true value. This experiment was used to determine the accuracy and precision of different volumetric measuring devices, as well as determining the density of an unknown metal. This lab was to help understand the application to volumetric measurements.
Part 1:
First, the next-to-smallest beaker was cleaned, dried, and weighed on the scale where it’s mass was determined. The container was then tared so the scale would only read the mass of the water. The smallest beaker was used to measure out 14 mL of water. Then, that waster was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded the beakers were both cleaned and dried. This process was repeated two more times.
Second, a 100 mL graduated cylinder was used to measure out 14 mL of water. Then, that water was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded, the beaker and graduated cylinder were both cleaned and dried. This process was repeated two more times.
Third, a 25 mL buret was used to measure out 14 mL of water. Then, that water was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded, the beaker and buret were both cleaned and dried. This process was repeated two more times....

...
Experiment
Density, Accuracy, Precision And Graphing
OBJECTIVES
1. The determination of the density of water
2. A comparison of the accuracy and precision of a graduated cylinder and a pipet
EXPERIMENTAL MATERIALS
Part A
A 50mL graduated cylinder
A balance
50.0mL deionized water
A rubber policeman
Part B
A 100mL beaker
A 50mL graduated cylinder
A volumetric pipet
120.0mL deionized water
A thermometer
A rubber policeman
EXPERIMENTAL METHODS
Part A: Density of water
1. An empty, dry 50mL graduated cylinder was obtained.
2. The mass of graduated cylinder with using a balance.
3. 10.0mL of deionized water was added to the 50mL graduated cylinder.
4. Mass of 10.0mL of deionized water + the cylinder was measured with balance.
5. To take only mass value of the 10.0mL deionized water, the mass value of the graduated cylinder was subtracted from the mass value of the 10.0mL of deionized water + the cylinder.
6. Density of 10.0mL of deionized water was calculated by its’ mass and volume. (d=m/v)
7. The exact density of the 10.0mL of deionized water was recorded on the data sheet.
8. Deionized water was added up to the 30.0mL mark of the 50mL graduated cylinder and Steps 3 to 7 were repeated for 30.0mL.
9. Deionized water was added up to the 50.0mL mark of the 50mL graduated cylinder and Steps 3 to 7 were repeated for 50.0mL....

...A MEMO FROM CORPORATE
Accuracy and Precision of “Volumetric” glassware
Jazet Nell Guimsop
Objectives:
In this laboratory experiment, the accuracy and precision of glassware made by a company manufacturing them will be assessed. This will be done by taking different volumes of water using a 10 mL graduated pipet, a 50 mL graduated buret, a 10 mL graduated cylinder, and a 50 mL graduated cylinder. After weighing each volume, we used the density of water at our room temperature to calculate the volume of each water samples. Then we compared that calculated volume (actual volume) to the one initially took; we used that result to assess the accuracy of our glassware by doing a t-Test. Also precision of the glassware was determined by calculating the standard deviation. At the end of this experiment, we expected our glassware to be accurate –corrected volume equal to zero; and precise – same volume obtained when the measurement is replicated.
Data:
We used a thermometer provided by our laboratory TA to get the water temperature which had a value of 22.3 ºC.
Table 1: Mass and Volume of Water delivered by a 10 mL graduated pipet
5mL | Mass of water (g) | Actual Vol (mL) | Corrected Vol |
Trial #1 | 4.9424 | 4.9539 | -0.046097 |
Trial #2 | 5.0299 | 5.0416 | 0.041607 |
Trial #3 | 5.0092 | 5.0209 | 0.020858 |
10mL | | | |
Trial #1 | 9.9410 | 9.9641 | -0.035863 |...

...Erica Alonso
Chemistry Honors 1
Mr. Cunningham
1.07 Accuracy and Precision
Procedure
Access the virtual lab and complete the experiments.
Data
• Below is the table that you will complete for the virtual lab. Either type your results into this table or print the table from the virtual lab (it must be submitted to receive full credit for this assignment.)
Part I: Density of Unknown Liquid
Trial 1 Trial 2 Trial 3
Mass of Empty 10 mL graduated cylinder (grams) 26 25.6 26
Volume of liquid (milliliters) 8.6 8.7 8.5
Mass of graduated cylinder and liquid (grams) 36.5 36.5 36.7
Part II: Density of Irregular-Shaped Solid
Mass of solid
(grams) 38.384 41.435 41.951
Volume of water (milliliters) 51 50 52
Volume of water and solid (milliliters) 57 55 58
Part III: Density of Regular-Shaped Solid
Mass of solid (grams) 28.1 26.1 26.2
Length of solid (centimeters) 5.25 5 4.5
Width of solid (centimeters) 3 4 3.5
Height of solid (centimeters) 2.5 3 2
Calculations
Show all of your work for each of the following calculations and be careful to follow significant figure rules in each calculation.
Part I: Density of Unknown Liquid
1. Calculate the mass of the liquid for each trial. (Subtract the mass of the empty graduated cylinder from the mass of the graduated cylinder with liquid.)
Trial 1- 10.5
36.5-26= 10.5
Trial 2- 10.9
36.5-25.6= 10.9
Trial 3- 10.7
36.7-26= 10.7
2. Calculate the density of the unknown...

...Lab No.1: density, accuracy and precision
Aim: to determine the relative precision and accuracy of different glassware items by calculating the density of a known substance.
Introduction: the density of a substance is its mass per unit volume. (where P-density, m- mass and v- volume). Different materials usually have different densities and densities vary according to the pressure, temperature and purity of a substance. When measuring, there is always a small uncertainty or error and therefore no measurement is exact.
Variables:
Independent: the type of liquid used
Dependant: the volume and density of the liquid
Controlled: the same type of beaker as the mass of the beaker is never changed
Hypothesis : the larger the divisions on the glassware items the bigger the percentage of error.
Materials:
Car oil
Coke Zero
Liquid soap
Salty water
1x 200ml beaker
1 x 100ml beaker
1 x 10ml cylinder
1 x weighing scale
1 x thermometer
Procedure:
1. Weigh a dry 100 ml beaker, a 10 ml graduated cylinder and a 10 ml pipette (in this case weigh a 150 ml beaker that you will transfer into a pipette, pipettes cannot be weighted effectively) and record the mass for each case. Do not forget that trailing zeros are significant figures and should be recorded.
2. Obtain a fair amount of water and measure its temperature.
(Remember here some students are measuring different substances, so the procedure...