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Experiment 2

Experiment 2. Density Calibration of Pipet & grad. Cylinder Thickness of Aluminum Foil. Reminders. ALL pages in the notebook must be numbered NEVER tear pages out of the notebook Make corrections by placing a single line through item

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Experiment 2

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  1. Experiment 2 Density Calibration of Pipet & grad. Cylinder Thickness of Aluminum Foil

  2. Reminders ALL pages in the notebook must be numbered NEVER tear pages out of the notebook Make corrections by placing a single line through item Anything with a line through it (including entire pages) is not looked at during grading

  3. Goals • To determine the average density of water • To determine average volumes deliveredby 10mL Volumetric Pipet and Graduated Cylinder (using previously determined DensityH2O value) and compare the associated errors • Use previously determined value (DensityH2O) to determine the thickness of aluminum foil

  4. Using a Pipet • What is a Pipet? • Long narrow open glass (or plastic) tube used to deliver liquids • Types • Volumetric vs. Graduated • TD vs TC • Use • Clean first until water sheething occurs (no beading) • Use pipet bulb, never mouth • Use forefinger, not thumb (because not as controllable)

  5. What is a Meniscus? • Water binds stronger to glass than it does to itself and forms a smile • Mercury binds to itself better and forms a frown • Bottom of meniscus indicates where liquid level is at • Take bottom of meniscus to fiduciary line of vol. pipet

  6. Part One Density of Water

  7. Density • Intensive Property vs. Extensive Prop • Intensive- • Extensive- • D=mass/volume = • So what do you need to measure? • Why do we use corks? • Why use 25.00mL instead of 1mL or 5mL?

  8. Reminder The analytical balance is a very precise instrument. It will consistently give the same values if used the same way every time. But, accuracy of mass measurements is dependent on you using the balance appropriately (zeroing, closing doors, etc.).

  9. Tables in the Notebook • Put DESCRIPTIVE titles on all tables • Pair data and results for each trail together • It is easier to find and compare data/results if all paired data is kept together in tables with descriptive titles

  10. Density Data Water Density Determination by Mass

  11. Part Two Calibration of Pipet and Cylinder

  12. Critical Measurements/Steps • What are they? • How can you tell?

  13. Calibration Data Experimental Values for Pipet Calibration * Similar Table for Grad Cylinder Calibration

  14. Calculations • D=mass/Volume = g/mL • Volume = Mass/Density (Use class Avg value) • Calculate Avg • Calculate Std. Dev. • What does this tell us? • Compare values for Pipet and Cylinder • When would it be most appropriate to use each?

  15. Part Three Thickness of Aluminum Foil

  16. How???? • Area of irregularly shaped piece of foil cannot be measured directly • Use ideas of Density (DAl = 2.702g/mL) and Thickness*Area (A= l*w) = Volume • D=mass/volume = mass/(A*thickness) Thickness = mass/(A*D) • So, how do you get area of irregularly shaped object?

  17. How Continued • Measure WHOLE sheet of paper and calculate area • Awhole paper=Lwhole paper*Wwhole paper • Trace foil shape on paper

  18. How Continued • Weigh beaker (mbeaker) • Weigh beaker + foil shape (mbeaker+foil) • mfoil= mbeaker+foil – mbeaker • Weigh beaker+paper shape (mbeaker+paper shape) • mpaper shape = mbeaker+ps- mbeaker • Add cut-off paper & weigh (mbeaker+whole paper) • mwhole paper = mbeaker+whole paper - mbeaker

  19. The Comparisons • mpaper shape= Dpaper*Vpaper shape = Dpaper*Apaper shape*Tpaper • mwhole paper = Dpaper*Vwhole paper = Dpaper*Awhole paper*Tpaper • mpaper shape Dpaper*Apaper shape*Tpaper mwhole paper Dpaper*Awhole paper*Tpaper

  20. Comparisons Continued • Then, do algebra: mpaper shape Apaper shape Apaper shape mpaper shape*Awholepaper mwhole paper Awhole paper mwhole paper • We can now determine Afoil • Afoil = Apaper shape

  21. Final Substitutions • Tfoil = mfoil/(Afoil*Dfoil) • mfoil = mbeaker+foil – mbeaker • Dfoil = 2.702g/mL (given, handout) • Afoil = Apaper shape

  22. Hazards: Understanding MSDSs • What is it? • What does it tell us? • Where can they be found?

  23. What is a Hazardous Material? • Corrosive • Water sensitive/reactive • MSDS warns of ecological effects • Flammable • Carcinogen – may cause cancer • Mutagen – may cause mutations • Teratogen – may cause reproductive effects or harm fetus • Toxic – may kill you or cause harm to a major organ • Inhalation hazard/lachrymator - must use protective equipment to protect • Which ones do we have to collect?

  24. How will the MSDS Tell Us? • Will clearly state the hazard • “May cause burns” = corrosive • “May cause damage to “major organ”” = toxic • “Studies in mice have indicated “hazard”” • Regulated by Clean Water Act or Clean Air Act = environmental hazard • “Harmful by inhalation/ingestion”

  25. Other Confusing Phrases • Target Organs • Where the substance will go when it enters the body • Does not mean that it harms that organ unless otherwise noted • Irritant • May irritate the skin (cause rash, etc.), eyes, nose, lungs if you are sensitive to the material • Chronic • Not a hazard – means repeated exposure • NFPA Ratings • You will not need to know, at this level, what each number represents • Follow this rule: if it is a value  3, definitely include it as a primary hazard

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