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Chapter 2 (p. 36-42)

Goal 1 : Develop abilities necessary to do and understand scientific inquiry. How Reliable are Measurements? Accuracy Precision Significant Figures. Chapter 2 (p. 36-42). Warm-up. Convert the following using dimensional analysis: 9.26 mm = _____ hm 0.089 mg = _____ kg

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Chapter 2 (p. 36-42)

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  1. Goal 1: Develop abilities necessary to do and understand scientific inquiry. • How Reliable are Measurements? • Accuracy • Precision • Significant Figures Chapter 2 (p. 36-42)

  2. Warm-up Convert the following using dimensional analysis: 9.26 mm = _____ hm 0.089 mg = _____ kg 4.5 x 1014 mL= _____ mL

  3. 1-Accuracy- closeness of measurement to accepted (correct) value 2-Precision- how close a set of measurements are to each other A. How reliable are measurements? game

  4. Accuracy vs. Precision

  5. Percent Error 3-Percent Error: • Measures the accuracy (how far off you are) of an experiment • Can have + or – value • + a little lower than accepted/- a little higher Accepted - Experimental x 100 Accepted Error__ x 100 Accepted go

  6. Example • Measured density from lab experiment is 1.40 g/mL. The correct density is 1.36 g/mL. • Find the percent error. go

  7. Answer What does the negative mean?

  8. B. Significant Figures • All known digits plus one estimated digit • Indicates precision

  9. Which is more precise? • 3.52 grams • 3.5 grams • 2 meters • 1.95 meters

  10. If there is a “decimal” present: • Start Pacific side: begin counting on the LEFT numbers 1-9, except leading zeros (any in between numbers are significant) • Ex: 0.002 3501 sec • 508.01 meters • 1.0200 x 105 kg Atlantic pacific rule for sig figs:

  11. If a decimal is absent in the number: • Start Atlantic side: begin counting on RIGHT with any number but zero (they don’t count); any zeros in between numbers 1-9 count • Example: 807 000 kg • 12 345 meters practice

  12. 1. 101.02 sec 2. 20.00 kg 3. 0.005 302 m/sec 4. 17 000 cm 5. 4320. 0 moles Practice-# of sig figs

  13. Need to use rounding to write a calculation correctly • When rounding, look at the digit after the one you can keep • Greater than or equal to 5, round up • Less than 5, keep the same Rounding

  14. Make the following have 3 sig figs: • 761.50  • 14.334  • 10789  • 203.514  Examples

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