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Chirp Chirp Welcome

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Chirp Chirp Welcome

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    1. Chirp! Chirp! Welcome!

    4. Data Analysis How to make measurements and treat data properly…

    5. Reading Assignment Oxtoby text : Appendix A1-4 Appendix B1-2 Lab Manual : Pages 29-42

    6. Precision & Accuracy Precision How close are the measurements to each other? Reproducibility Accuracy – How close is a measurement to the true value? Could be affected by the following: Systematic errors – all higher or lower than actual value Random errors – some high and some low

    7. Significant Figures Presenting measurements and calculated results with the appropriate significant figures and units is an indication of the precision of values.

    8. Rules for Sig Figs All nonzero digits are significant Trapped zeros are significant Trailing zeros are significant if there is a decimal point Leading zeroes are NOT significant

    9. Scientific Notation 3.0 x 10 2 has two sig figs Written as a number between 1-10 x a power of ten Unambiguously displays the precision of the value making it easier to make comparisons 300 3 x 102 300. 3 .00 x 102 300.0 3.000 x 102 0.003 3 x 10-3 0.0030 3.0 x 10-3 0.00300 3.00 x 10-3

    10. Making Measurements - Thermometer The number of significant figures in your measurement depends on the measuring device.

    11. Beaker vs. Graduated Cylinder Each contains the same amount of water.

    12. Beaker

    13. Graduated Cylinder 1/10 of .5 is .051/10 of .5 is .05

    14. The Analytical Balance

    15. Calculations & Sig Figs Multiplication & Division The total number of sig figs in the answer is equal to the same number of sig figs in the measurement used in the calculation with the smallest number of sig figs. Ex: 5.1 cm x 2.01 cm = 10.0701 cm2 = 10. cm2 • Round the final answer using the number to the right of the last sig fig. • Avoid round off errors by keeping extra digits beyond the last sig fig when calculating intermediate values.

    16. Calculations & Sig Figs Addition & Subtraction The final answer should be rounded to the right-most filled column (according to the value with the biggest uncertain digit – the weakest link). Ex: 6.5 cm 100.01 cm + .044 cm 106.554 cm = 106.6 cm

    17. “Scientific notation” can make it easier….. What is the sum of 4.5 x 10-6, 3.2 x10-5, and 15.2 x 10-7? .45 x 10-5 3.2 x 10-5 .152 x 10-5 3.802 x 10-5 = 3.8 x 10-5 Make note that the first and third numbers aren’t technically in scientific notationMake note that the first and third numbers aren’t technically in scientific notation

    18. SI Prefixes Prefix Symbol Meaning Power of 10 Mega M 1,000,000 106 Kilo k 1,000 103 Deci d 0.1 10-1 Centi c 0.01 10-2 Milli m 0.001 10-3 Micro ľ 0.000001 10-6 Nano n 0.000000001 10-9 Femto f 0.000000000000001 10-15 Atto a 0.000000000000000001 10-18

    19. Fundamental SI Units Physical Quantity Unit Abbreviation Mass kilogram kg Length meter m Time second s Temperature kelvin K

    20. Dimensional Analysis Use conversion factors (definitions, ratios) to convert from one unit to another. Conversion factors are exact numbers that have no uncertainty. Ex. Convert 6.4 weeks to hours. 6.4 weeks x 7 days x 24 hours = 1100 hrs 1 week 1 day

    21. Group Problems Convert 47 hours to weeks. 47 hours x 1 day x 1 week = 0.28 weeks 24 hours 7 days The same conversions were used as in the previous example. The top equals the bottom. Round off answers at the end. Keep additional sig figs for intermediate answers. Calculate the sum of 2.0 + 3.5 + 4.5 +5.5. 2.0 3.5 4.5 5.5 15.5 The tread on a certain automobile tire wears 0.00100 inches per 2,600 miles driven. If the car is driven 45 miles a day, how many months ( 1mo = 30 days) can a tire w/ 0.010 in of treat be used before it wears down and needs to be replaced? .010in x 2,600 mi x 1 day x 1 month = 19.25 = 19 months 0.00100in 45 mi 30 days In a displacement of water by gas experiment the initial volume of water in a burette is 45.50 mL and the final volume is 37.50 mL. What is the total volume of water displaced? In mL? in L? 45.50 (4sf) - 37.50 mL (4sf) 8.00 mL (3sf) = 0.00800 L (still 3sf)

    22. Statistical Analysis and Expression of Data Reading: Lab Manual 29 - 40 Today: Some basics that will help you the entire year

    26. First Day in the Laboratory (p.1-3) Let’s move to Room 122 for the balance exercise. Complete p. 3 and turn in to your lab assistant before you leave.

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