1. Scientific & Chemical Fundamentals Measurement, Conversions & Calculations Dr. Ron Rusay Fall 2007 © Copyright 2003-2007 R.J. Rusay

2. Measurement & Units SI units & common units in General Chemistry (Lab Manual pp. 139-142) Quantitative vs. Qualitative MASS (Chem: gram; SI: kg) LENGTH (Chem: cm & others; SI: m) TEMPERATURE (Celsius & Kelvin; SI: K) VOLUME (Chem: mL; SI: Liter) CHEMICAL AMOUNT: Mole (mol) © Copyright 1998-2007 R.J. Rusay

3. Units of Measure

4. Mass and Volume Measurements: Refer to pp. 5-8

5. Mass Determination (Weighing Devices: Balances)

6. Volumes of regular shapes h V = l x w x h V = s 3

7. Volume

8. Liquid Measurement Tools

10. Numbers & Measurement The Importance of Units  Measurement - quantitative observation consisting of 2 parts Part 1 - numberPart 1 - number Part 2 - unitPart 2 - unit  Examples: 20 grams20 grams 6.63    joules / second6.63    joules / second

11. Scale: Size & Comparison  Macroscopic vs. Microscopic  IBM financed Video: http://www.wordwizz.com/imagendx.htm How would you compare your lifespan?.. to that of a dog? ….to the age of the earth?…How about the age of mankind to that of all life?....the age of industrialized mankind to the age of mankind?

12. Graphic Comparisons

13. Powers of Ten: Scale

14. Shorthand Prefixes Language describes scale (prefixes) How many zeroes does yotta yotta yotta have?

15. Commonly used prefixes in Chemistry These should be known from memory.

16. Commonly used prefixes in Chemistry Attosecond spectroscopy = 10 -15 x 10 -3 seconds Science, 317, 765-775, (2007) “The Electron Stopwatch”

17. QUESTION Conveniently, a U.S. nickel has a mass of approximately 5 grams. If you had one dollar’s worth of nickels what would be the mass of the nickels in milligrams? 1.100 milligrams 2.50 milligrams 3.1,000 milligrams 4.100,000 milligrams 1000 milligrams (mg) = 1 gram (g)

18. Scientific Notation & Significant Digits Scientific Notation: A single digit followed by a decimal and a power of ten. Examples: 2,345 mL and 0.002340 g 2,345 mL = 2.345 x 10 3 mL 0.002340 g = 2.340 x 10 -3 g

19. Numbers Expressing a number correctly is determined by the method used in the measurement! How many numbers should I include? Significant Digits (Figures) Consider: the exactness of the measured value Short Hand expression translates the number: Scientific Notation © Copyright 1998-2007 R.J. Rusay

20. What is the length of the rod? Different measurement tools give different numbers: Which ruler is better? ? cm 4.2 - 4.3cm 4.24 - 4.25cm

21. What is the diameter of a circle? All measuring devices are not the same, and the values (numbers) that come from them indicate their limitations. Is there a better instrument to use other than a ruler?

22. What does each line represent? 1 mL What can be estimated? O.1 mL

23. Measurement Assignment http://chemconnections.llnl.gov/General/Chem120/volume1.htm http://chemconnections.llnl.gov/General/Chem120/volume1.htm

24. Temperature Scales Relative to Water

25. “Normal” Body Temperature

26. QUESTION Dr. R. walks into class and claims, “It is very cold in here today. It feels like 242 K.” If that were the temperature, would you agree that you would feel cold? What would that be in Celsius degrees? 1.I agree, that would be 31°C. 2.I agree, that would be – 31°C. 3.I do not agree, that would be 31°C. 4.I agree, that would be –31.15°C.

27. Temperature

28. Reporting Numbers Rules for Significant Digits (Figures)  Nonzero integers always count as significant figures.  3456 g has how many sig figs?  4 sig figs. Expressed in scientific notation?Expressed in scientific notation? 3.456 x 10 3 g

29. Reporting Numbers Rules for Significant (Digits) Figures  Exact  Exact numbers (unit, conversion or scale factors) factors) can have an infinite number of significant figures. 1 1 1 1 liter = 1,000. 1,000. ml, exactly 1 1 1 1 inch = 2.54 2.54 cm, exactly

30. Zeros  Leading zeros do not count as significant figures.  0.0486 mL has how many sig figs?  3 sig figs. Number expressed in scientific notation?Number expressed in scientific notation? 4.86 x 10 -2 mL

31. Zeros  Captive zeros always count as significant figures.  16.07 cm has how many sig figs?  4 sig figs.  Number expressed in scientific notation? 1.607 x 10 1 cm

32. Zeros  Trailing zeros are significant only if the number contains a decimal point.  9.300 kg has how many sig figs?  4 sig figs. Number expressed in scientific notation?Number expressed in scientific notation? 9.300 kg

33. QUESTION Which one of the following does NOT represent a result with four significant digits? 1.0.07100 2.0.7100 3.0.7010 4.0.0710

34. Mathematics & Arithmetic Relative to method(s) of measurement Short Hand expression: Scientific Notation Numbers : How many to include? Quantitative vs. Qualitative Addition/Subtraction...... Multiplication/Division..... What is “significant”?..... Rounding Off http:dbhs.wvusd.k12.ca.us/SigFigsFable.html © Copyright 1998-2007 R.J. Rusay

35. Systematic Problem Solving Dimensional/Unit Analysis: Conversions Workshop pp. 145-149 How many mL of milk are in a1/2 gallon carton? ? mL 0.50 gal 1 gal = 4 qt 1 qt = 946 mL 0.50 gal | 1 qt | 946 mL | 4 gal | 1 qt | 4 gal | 1 qt = ? mL

36. Complete the following Units & Conversions 13,000,000,000 yrs.________________ __? gigayears 13 Gyrs Number Scientific Notation Named unit 1.3 x 10 10 yrs ___________ mL ______________ mL 0.546 Liters ____________ kg__8.45 x 10 -1 kg___ _? grams__ 5.46 X 10 2 546 0.845 845 g 0.546 L

37. Computational Rules Addition/Subtraction: Answer expressed to the least number of decimal places of the figures in the process Multiplication/Division: Answer expressed to the least number of significant figures © Copyright 1998-2007 R.J. Rusay

38. Addition  Four students were each asked to measure a piece of wire and provide a total length for the four pieces.  Report the result correctly: 16.346 cm

39. QUESTION If you were unloading a 23.50 kg box of books from your car and a “friend” added two more 482 gram chemistry books, how much in kg and using the rules for significant digits, would you be lifting? 1.23.98 kg 2.24.464 kg 3.24.46 kg 4.24.5 kg

40. Mathematical Processes:  Provide correct answers assuming each value (unit omitted) is written with the correct number of sig figs: 9.56370 9.61370

41. QUESTION The average mass of a certain brand of vitamin C tablets is 253 mg. What is the mass of three such tablets rounded to the proper number of significant digits? 1.0.760 grams 2.0.759 grams 3.0.7590 grams 4.0.253 grams

42. Conversion Factor Method (Dimensional Analysis) Qualitative Descriptions vs. Quantitative Use exact numbers / “scale factor” UNITS A Bookkeeping Method: Example Short” ___ ft___in --------> ? m (1 ft = 12 in; 2.54 cm = 1 in; 100 cm = 1 m) ___ft x 12 in/ft + ___in = ___in ___in x 2.54 cm/in x 1 m/100cm = ___m © Copyright 1998-2007 R.J. Rusay 5 5 5565 65 1.651