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Laboratory Techniques and Measurements

Name: Kensley Shelley|Date: 9-17-12| Exp 2: Laboratory Techniques & Measurements|Lab Section: 0000| Data Tables: Step 1: Length and Measurements Object Measured|Length in cm|Length in mm| Key|5. 15 cm|51. 5 mm| CD|12.

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0 cm|120. 0 mm| Fork Spoon|18. 05 cm 16. 30 cm|180. 5 mm 163. 0 mm| Step 2: Warm Temperature Measurements Hot tap water temperature49. 50_? C Boiling water temperature __immediately:104. 5; after 5 minutes: 103. 0__? C Step 3: Cold Temperature Measurements Cold tap water temperature_24. 5_? C Ice water temperature after 1 min:4. 5, after 5 min:1. 0 ? C Step 4: Volume Measurements

Volume of half filled graduated cylinder__12. 5__mL Volume of completely filled small test tube __n/a__mL Number of drops in 1 mL___14_drops Volume of the micro pipet __28__ drops_2___mL Step 6: Density Measurements Part A Mass of empty graduated cylinder_16. 9_g Mass of graduated cylinder and water 21. 1_g Net mass of the water __4. 2_g Density of the water_0. 84_ g/mL Part B Mass of graduated cylinder and alcohol _20. 4_g Net mass of the alcohol __3. 5_g Density of the alcohol__0. 7__ g/mL Part C Mass of graduated cylinder and salt solution ____g Net mass of the salt solution____g

Density of the salt solution____ g/mL Part D Volume of half filled graduated cylinder__8. 0__mL Volume of half filled graduated cylinder and metal bolt_9. 1__mL Volume of the metal bolt_1. 1_mL Mass of the metal bolt __7. 2__g Density of the metal bolt__6. 55__g/mL Part E Mass of half filled beaker__89. 0__g Mass of water displaced by metal bolt__90. 1__g Volume of the metal bolt__1. 1__cc Density of the metal bolt__6. 55__g/cc Mass of half filled beaker__89. 0__g Mass of water displaced by magnet__89. 8__g Volume of the magnet _0. _cc Mass of the magnet __4. 0_g Mass when dropping the magnet in the beaker__92. 9__g Density of the magnet__5. 00__g/cc Calculated volume of the magnet using dimensions of length x width x height__0. 78__cc Density of magnet using the calculated volume_5. 13___g/cc Conclusion: Questions and Problems: A. Which method of determining density is more accurate, the water displacement method in Part D or Archimedes’ principle method in Part E? Why? For the metal bolt, I received the same answer for both experiments, so I would say both were equally accurate in my experiment.

B. What is the relationship between mL and cm3? They equal each other; mL = cc C. Everyone knows that water is supposed to boil at 100° C. Why did your water sample boil at a different temperature? Water boils at different temperatures depending on the altitude. The higher pressure in the air keeps the molecules from escaping as easily. D. To help you get a feel for metric measurements, you need to know the relative magnitude of a few basic measurements. For example: 1 mm = thickness of a dime, a penny weighs 2 ? grams, and 20°C = normal room temperature. Determine the following: . What is the mass in kilograms (kg) of a person who weighs 143 lb? 64. 86 kg 2. What weighs approximately 1 g? dollar bill, paper clip 3. What is approximately 1 cm long, wide or thick? fingernail is 1 cm wide 4. What weighs about 100 g? 20 nickels, 40 pennies 5. What weighs about 1000 g? 1 liter of water Conclusion: The experiment was designed to help acquaint the student with proper laboratory measurements and techniques. This was done by allowing the student to use the different lab tools in a variety of ways, such as: heating, measurements, volume, and density.

In completing this lab, I am better aware of the different tools which will be used and how to properly use them, because a slight mistake in measuring can skew your data. I witnessed this in the density calculations in that the wrong mass or volume could greatly skew the results of the density. I first recorded 7. 6 g as the mass for the metal bolt, but on second glance I realized it was only 7. 2 g. While this may not seem significant at first, having a difference of 0. 4 g is very significant in determining the correct density. I also observed how important it is to account for one uncertain digit.

When measuring items using the cm side of the ruler, I had to account for an uncertain digit when it measured in between two lines. Accounting for this uncertain digit helps to gain a more accurate reading. Also, reading at the bottom of the meniscus is also very important when measuring. When I first used the beaker, I did not get down to eye level and therefore I could not properly see the meniscus, but after putting it to eye level, I could see that I was slightly off on my measurement. I also learned how to determine the mass of certain objects that are not easily measured.

I did so by first measuring the cylinder’s mass and then measuring the mass of the cylinder with the liquid in it. I was then able to subtract the two and get a good measurement of the mass of the liquid. Another technique practiced was using displaced water to determine the volume and subsequently the density of an object. By putting the object on a string and placing it in the water, I was able to record the mass of the displaced water (90. 1 g), which i was then able to convert to the volume of the object (1. 1 mL). This number along with the mass of the object (7. g), could then be converted to the density of the object (6. 55 g/cc). There were a few potential errors that could have occurred while preforming the experiments. First, when calibrating my at home scale, I had to place an object that was 500 g on the scale. While I believe the object I placed on it was close to that mass, it could have been off slightly which could have skewed my results. Also, there is always the possibility of miscalculations when I was determining the volume of the magnet using the ruler. There is always the chance of miss counting something which can led to inaccurate results.