Chemistry 161 Intro Lab

1. Chemistry 161Intro Lab Monique Wilhelm

2. NEVER MISS LAB!!!!! • One hour lecture • Remaining time in lab • 1credit class = at least 3 hours spent outside of class on class preparation • Classroom Environment • Lecture-open discussion style • I EXPECT you to talk, too • Help answer questions, etc. • Do not be turned off if I answer a question with another question; my job is to show you how to problem-solve

3. What will we learn? • Methods and equipment used in chem labs • How to make decisions about experimentation • What types of things are important to be aware of during experimentation • How to draw conclusions about data obtained • How to communicate your findings

4. Safety Overview • Remember: Everything in Chemistry Lab has the potential to be harmful • Goggles • Gloves • Absolutely No Eating or Drinking in Any Lab • 5 Senses • Attire • Long Hair Tied Back • Always wear long pants • Never wear loose fitting long sleeved shirts • NO sandals, closed shoes

5. Safety Continued • Remember: Everything in Chemistry Lab has the potential to be harmful • Labels • Contact • Excess Chemicals • Material Safety Data Sheets (MSDSs) • Explain the hazards associated w/ substances • ALL chemicals have the POTENTIAL to be harmful

6. Expectations Follow Directions Be Prepared Only one late assignment allowed NO make ups Types of Grading Notebooks -Observations & Data hand-written Lab Reports- TYPED Computer assignments Quizzes – 2 types Final Project Possible Extra Credit Your Grade

7. Today’s Experiment How to Use a Balance & Comparison of Data to Standards

8. Scale Measures weight Balance Measures mass Difference Between Balance & Scale Relationship? Weight = mass*gravity

9. Precision Multiple readings giving same measurement Accuracy How close to real number Difference Between Precision & Accuracy A balance is a relatively precise instrument In this lab, you are interested in accuracy

10. How to Get Good Accuracy • Top Loading Balances • Used to weigh grossly • Analytical Balances • Can weigh very small quantities • Weighing by Difference • Expected Error = Relative Uncertainty (error associated with instrument/measurement)*100%

11. Two Types of Balances • Top Loading Balance • Measures Grossly • Picture From http://www.hitechtrader.com/imagepage.cfm?pic=45246.jpg • Analytical Balance • Measures Accurately • Picture From http://www.chem.vt.edu/RVGS/ACT/lab/Analytical_Balance.html

12. Comparison of Data • Compare your average values to class averages • Which one do you EXPECT to be closer to actual value and why? • Compare to U.S Mint values Be sure to cite reference for values

13. Coin Demo • I will demonstrate the use of balances in lab

14. Significant Figures • Always record data as accurately as you can (as many sig. figs. as method allows) • The last digit of the value that you record should be estimated • Do not round values until calculations are completed • Examples Follow

15. Sig Figs Examples • Addition and Subtraction • Use least # of decimal places • 15.287+13.07= 28.36 • Multiplying and Dividing • Use least # of sig. figs. • 0.0387*1.0= 0.039 • (100.8+0.524)*10.05 = 4 sig figs • 100.8+0.524 = 101.3 • 101.3*10.05 = 1018

16. Relative & Absolute %Error • Precision Determination • How far are values off from each other • Standard Deviation OR • Relative % Error • = (largest – smallest)*100%/average • Accuracy Determination • How far off from real value? • Absolute %Error • = (|experimental value – real value|)*100%/real value

17. Standard Deviation • Error Analysis-how far the values differ from the averages (related to %relative error, precision) • Normal Distribution Assumed • AverageNormal • S= ((xi-x)2)/(N-1) • Give values as Average ± Std Dev

18. Using Excel for Data Analysis in CHM 161

19. What is Excel? • Computer program by Microsoft • Spreadsheet program used to present data and produce graphs • Can also be used to perform calculations using function “programming” • Available on all campus computers

20. Why use Excel? • Makes for better presentation of results • Cleaner, more accurate graphing • Ability to calculate more accurate values from graphs

21. Lesson 1 Making Tables • X values (independent variables) to the left of Y values (dependent variables) • Use top row to indicate which values you will have in which columns • Be sure to add units to labels • Click on cell (rectangle) and type (word or value)

22. Lesson 2: Performing Calculations • Click on cell that you would like to have the value for the calculation placed • Type “=“ to let program know that you want it to perform calculation • Select “Insert” on toolbar • Scroll down to “Function” and click

23. Lesson 2: Performing Calculations cont’d • Click on categories to find function desired • For this class, most common will be SUM and AVERAGE • Double click on function to select • Click on red-white-blue box to select values that you want program to use for calculation • Use cursor to highlight boxes with desired values • Click red-white-blue box to accept values • Click OK to complete

24. Lesson 3: Making Graphs • Input data as previously described • Use cursor to highlight values to be plotted • Select “Insert” on toolbar • Scroll down to “Chart” and click • Click on type desired (best for this class is “XY Scatter”) • Click on picture to right to choose desired style (Use points without lines) • Click “Next”

25. Lesson 3: Making Graphs Cont’d • Look to be sure that data is lined up on the right axes • If not, Select “rows” or use “series” tab to rearrange data • Click “Next” • Fill in Title (Descriptive enough to tell what info can be obtained from graph, not x vs. y, etc.) • Example: “Standard Curve for the Determination of Cobalt Concentration”

26. Lesson 3: Making Graphs Cont’d • Click on tabs to change/remove legend/gridlines, etc. • Click “Next” • Select “As New Sheet” and click “Finish” • Right click on desired area if changes are necessary • Click on grey area and then the bucket and select “No Fill” to remove grey and save printer ink

27. Lesson 4: Best Fit Lines • Used for all standard curve graphs made in this class • Make graph as previously described • Click on data point • Select “Chart” on toolbar • Scroll down to “Add Trendline” and click • Select box of desired curve (ie “linear”)

28. Lesson 4: Best Fit Lines cont’d • Click on “Options” tab • Click “Display Equation on Chart”, “Display R-squared value”, etc. to turn these options on • R-squared tells how well your data fits the line generated • Can be used as indicator of accuracy for data • Click on “OK” • Click on Equation, etc. displayed on chart and drag to desired (visible) location

29. Adding to Notebook • After you have completed your editing, select “File” on toolbar • Scroll down to “Save” and click and save as you would any other file • Select “File” on toolbar • Scroll down to “Page Setup” and click • Click on “Chart” tab • Select “Custom”

30. Adding to Notebook cont’d. • Click on “Options” • Scroll down to “2” in “Pages per Sheet” • Will print 2 graphs per sheet of paper to fit in notebook • Click “OK” until back to graph • Select “File” on toolbar • Scroll down to “Print” and click • Follow usual printing procedures

31. Adding to Papers • Click on outer edges to select whole graph • Select “Edit” on toolbar • Scroll down to “Copy” and click • Open program that you desire to use to write paper (ie MS Word) • Click area of report where you wish to insert graph • Select “Edit” on toolbar • Scroll down to “Paste” and click • Click corner and drag to scale to appropriate size