Uncertainty and Measurement Lab Report PDF

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Uncertainty and Measurement Lab Report...

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Prelab: 1. One piece of glassware that is marked to measure a set volume is a graduated cylinder. You can also use a beaker to measure a set volume, however, using a graduated cylinder is more precise than using a beaker. One piece of glassware that is not marked to measure a set volume is a glass funnel. A glass funnel is used to pour a liquid into another container with a smaller opening. 2. Glassware that is meant to deliver is not marked as precisely as glassware that is meant to contain. For instance, the purpose of a glass funnel is to pour liquid into another container with a smaller opening while the purpose of a graduated cylinder is to measure a set volume. The glassware that is most prevalent in my drawer are beakers and test tubes. 3. In my drawer there are several pieces of labware that are not made of borosilicate glass such as the corks and stoppers, the crucible, the tongs, the tweezers, etc. It is easy to tell which pieces of labware are not made of borosilicate glass because they are made of other materials such as cork or porcelain. For instance, the crucible is made of porcelain so it is able to withstand a very high temperature. The tongs are made of metal so they are stronger and can hold more weight. Glassware is used more for measurement, containing, or the transferring of substances. Observations: Part one: Piece of Equipment

Estimation

Small Test Tube

5 mL

Large Test Tube

20 mL

50 mL Beaker

34 mL

100 mL Beaker

36 mL

250 mL Beaker

27 mL

400 mL Beaker

31 mL

125 mL Erlenmeyer Flask

32 mL

250 mL Erlenmeyer Flask

35 mL

Wash Bottle

38 mL

10 mL Graduated Cylinder

9.5 mL

50 mL Graduated Cylinder

39.5 mL

Part two:

Piece of Equipment

Uncertainty

Best Use

Justification

Small Test Tube

87.5

Contain

The test tubes were the most uncertain and should not be used for measurement. Instead, they should be used to contain substances.

Large Test Tube

50

Contain

The test tubes were the most uncertain and should not be used for measurement. Instead, they should be used to contain substances.

100 mL Beaker

10

Contain

The beakers provided estimates that were uncertain. Because of this, they should be used to contain solutions and they should not be used for measurements.

125 mL Erlenmeyer Flask

20

Contain and mix solutions

The Erlenmeyer flask provided estimates that were uncertain. Because of this, they should be used to contain and mix solutions.

50 mL Graduated Cylinder

1.25

Measure and deliver

The graduated cylinder was the most reproducible, making it a good tool for measurement.

Wash Bottle

5

Rinse

While the wash bottle had the second most reproducible estimate, its best use is to rinse off other pieces of equipment.

Part three: Piece of Equipment

Actual

Expected

|Expected - Actual | / Actual x 100

Watch Glass

36.474g

35.474g

2.742 %

Forcep

21.004g

20.004g

4.761%

Clamp

14.985g

13.985g

6.673%

Striker

65.716g

64.716g

1.522%

Crucible Cover

15.661g

14.661g

6.385%

Cork

0.651g

0.551g

15.361%

Rubber Stopper 6

21.730g

20.730g

4.602%

Stirring Rod

6.788g

5.788g

14.732%

Funnel

55.832g

54.832g

1.791%

Dropper with Bulb

3.392g

2.392g

29.481%

When conducting part one of the experiment, I quickly realized that it was much more difficult to estimate 40 mL of distilled water when using certain instruments. For instance, when using instruments such as the test tubes and beakers, one does not get very estimates very close to 40 mL. However, when using instruments such as the Erlenmeyer flask, the wash bottle, or the graduated cylinders, one gets estimates that are much closer to the desired amount of 40 mL. When conducting part two of the experiment, pieces of equipment such as test

tubes, beakers, wash bottle, and Erlenmeyer flasks have purposes other than measuring solutions. The graduated cylinders provided the most accurate estimates, making it best used for measurement. I was surprised to discover that the wash bottle had the second most reproducible estimate. While it did have the second most reproducible estimate, it is best used for rinsing other pieces of equipment. When conducting part three of the experiment, the three items with the highest mass were the striker, the funnel, and the watch glass. To find the uncertainty, take the expected value and subtract it from the actual value then divide that total by the actual value. Finally, multiply the entire total by 100. The three items with the highest uncertainty are the dropper with the bulb, the cork, and the stirring rod. The three items with the lowest uncertainty are the funnel, the striker, and the watch glass. Data Analysis: 1. The graduated cylinder was most reproducible because it allowed for the most accurate estimation. The least reproducible items were the test tubes. 2. The dropper had the highest percent of uncertainty because it holds air, making it weigh less. Discussion Questions: 1.The picture shows an example of what a piece of glassware looks like on a molecular level.

2. This picture shows two beakers. The beaker on the left shows what water molecules look like when they are in a beaker. Water molecules have a lot of kinetic energy (more than solids) but they have less potential energy than a solid. Water molecules move freely and they bump into each other. They take the shape of the container they are in. The beaker on the right shows what a liquid looks like in a beaker.

3. Because graduated cylinders allow for the most accurate estimates of volume, they are made to deliver. If they were made to contain, they wouldn’t have the most accurate measurements. Pieces of equipment that are used to contain are beakers. 4. In this experiment, I found that measurements can be uncertain and every piece of equipment has a certain use. In part one of the experiment, pieces of equipment such as beakers, test tubes, and Erlenmeyer flasks were used to hold 40 mL of water. When estimating 40 mL of water with these pieces of equipment, it was evident that they are not very reproducible and should not be used for measurements. However, graduated cylinders were the most accurate piece of equipment to measure with, as they had estimates closest to 40 mL. In part two of the experiment, the uncertainty was found for different pieces of glassware. The glassware with the highest uncertainty were the test tubes. The small test tube had an uncertainty of 87.5 and the large test tube had an uncertainty of 50. The next highest uncertainty was the Erlenmeyer flask with an uncertainty of 20. Because these uncertainties are so large, these pieces of equipment should not be used to measure, but instead they have other uses such as containing or mixing solutions. In an article written by the University of Tartu, the uncertainty of measurement is discussed. “Random effects cause the difference between repeated measurement results,” which can be seen in the amount of uncertainty with the test tube. The article mentions that in order to decrease the influence of random effects, multiple trials need to be conducted. If this experiment was repeated, it would be necessary to conduct multiple trials to decrease the uncertainty. In part three of the experiment, the three pieces of equipment with the highest mass are the striker, the funnel, and the watch glass while the pieces of equipment with the lowest mass are the cork, the dropper with the bulb, and the stirring rod. The three pieces of equipment with the highest uncertainty are the dropper with the bulb, the stirring rod, and the cork. The three pieces of equipment with the lowest uncertainty are the funnel, striker, and the watch glass. This experiment showed that measurements

can be uncertain, which is why it is important to use the proper equipment and the correct, precise measurements. References: University of Tartu. “The Origin of Measurement Uncertainty .” Synthetic Sapphire vs. Glass, Fused Quartz & Silica | Rayotek Scientific Inc....