1 / 21

210 likes | 397 Views

CH. 2 - MEASUREMENT. I. Using Measurements. A. Accuracy vs. Precision. Accuracy - how close a measurement is to the accepted value Precision - how close a series of measurements are to each other. ACCURATE = CORRECT PRECISE = CONSISTENT. A. Accuracy vs. Precision. Not Precise

Download Presentation
## CH. 2 - MEASUREMENT

**An Image/Link below is provided (as is) to download presentation**
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.
Content is provided to you AS IS for your information and personal use only.
Download presentation by click this link.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

**CH. 2 - MEASUREMENT**I. Using Measurements**A. Accuracy vs. Precision**• Accuracy - how close a measurement is to the accepted value • Precision - how close a series of measurements are to each other ACCURATE = CORRECT PRECISE = CONSISTENT**A. Accuracy vs. Precision**Not Precise Not Accurate Precise Accurate Precise Not Accurate**your value**accepted value B. Percent Error • Indicates accuracy of a measurement**% error = 2.9 %**B. Percent Error • A student determines the density of a substance to be 1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL.**C. Significant Figures**• Indicate precision of a measurement. • Recording Sig Figs • Sig figs in a measurement include the known digits plus a final estimated digit 2.35 cm**C. Significant Figures**6.34 cm**C. Significant Figures**• Rule 1- any # other than 0 is significant • Example 123.45 has 5 SF**C. Significant Figures**• Rule 2- any 0’s between significant figures are significant • Example- 1002.05 has 6 SF • 1002 has 4 SF**C. Significant Figures**• Rule 3- All final 0s after a decimal are significant • Example- 12.740 has 5 SF • 92100. has 6 SF**C. Significant Figures**• Rule 4- )s used for spacing are not significant • Example- 921000 has 3 SF • .00000233 has 3 SF**C. Significant Figures**Counting Sig Fig Examples 1. 23.50 1. 23.50 4 sig figs 3 sig figs 2. 402 2. 402 3. 5,280 3. 5,280 3 sig figs 2 sig figs 4. 0.080 4. 0.080**C. Significant Figures**• Rounding • If the digit to be removed is: • < 5, round down • > 5, round up • = 5, round to the nearest even number**C. Significant Figures**Rounding Examples Round each number to 3 sig figs 42.7 g 1. 42.68 g 17.3 m 2. 17.32 m 2.78 cm 3. 2.7851 cm 78.6 kg 4. 78.5543 kg**3 SF**C. Significant Figures • Calculating with Sig Figs • Multiply/Divide - The # with the fewest sig figs determines the # of sig figs in the answer. (13.91g/cm3)(23.3cm3) = 324.103g 4 SF 3 SF 324g**C. Significant Figures**• Calculating with Sig Figs (con’t) • Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer. 224 g + 130 g 354 g 224 g + 130 g 354 g 3.75 mL + 4.1 mL 7.85 mL 3.76 mL + 4.1 mL 7.86 mL 350 g 7.9 mL**C. Significant Figures**• Calculating with Sig Figs (con’t) • Exact Numbers do not limit the # of sig figs in the answer. • Counting numbers: 12 students • Exact conversions: 1 m = 100 cm • “1” in any conversion: 1 in = 2.54 cm**5. (15.30 g) ÷ (6.4 mL)** 2.4 g/mL 2 SF C. Significant Figures Practice Problems 4 SF 2 SF = 2.390625 g/mL 6. 18.9 g - 0.84 g 18.1 g 18.06 g**D. Scientific Notation**• Converting into Sci. Notation: • Move decimal until there’s 1 digit to its left. Places moved = exponent. • Large # (>1) positive exponentSmall # (<1) negative exponent • Only include sig figs. 65,000 kg 6.5 × 104 kg**7. 2,400,000 g**8. 0.00256 kg 9. 7 10-5 km 10. 6.2 104 mm D. Scientific Notation Practice Problems 2.4 106 g 2.56 10-3 kg 0.00007 km 62,000 mm**EXE**EXP EXP ENTER EE EE D. Scientific Notation • Calculating with Sci. Notation (5.44 × 107 g) ÷ (8.1 × 104 mol) = Type on your calculator: 5.44 7 8.1 4 ÷ = 671.6049383 = 670 g/mol = 6.7 × 102 g/mol

More Related