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Unit 2: Basic Math for Chemistry Lesson 1: Significant Figures

Unit 2: Basic Math for Chemistry Lesson 1: Significant Figures. Do Now: Express 44,300 in scientific notation. Book Section: 3.1. Accuracy vs. Precision. Accuracy is how close a measurement is to the “correct” value. Precision is how close measurements are to each other.

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Unit 2: Basic Math for Chemistry Lesson 1: Significant Figures

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  1. Unit 2: Basic Math for ChemistryLesson 1: Significant Figures Do Now: Express 44,300 in scientific notation. Book Section: 3.1

  2. Accuracy vs. Precision Accuracy is how close a measurement is to the “correct” value. Precision is how close measurements are to each other.

  3. Accuracy vs. Precision

  4. Significant Figures In science, measurements have precision, based on the tools we use. The precision of the numbers is determined by the number of significant figures there are.

  5. Counting Significant Figures • All non-zeroes are significant (1-9). • 423 • Zeroes in the beginning… NEVER!! • 0.124 • 0.000000053 • Zeroes in the middle… ALWAYS!! • 1204 • 6.0043 • 0.00809 • Zeroes at the end… SOMETIMES!! (if there’s a decimal point) • 12400 • 1.2400 • 30400.

  6. How Many Sig Figs? 28.6 g 3400. cm 910 m 0.04604 L 0.0067000 kg

  7. Adding and Subtracting Sig Figs Your answer will be rounded to the place value of the least precise of the original numbers. • 25.1 g + 2.03 g • 25.1 is precise to the tenths place • 2.03 is precise to the hundredths place • Your answer needs to be rounded to the tenths place.

  8. Practice - Adding and Subtracting Sig Figs 2.099 g + 0.05681 g 5.44 m – 2.6103 m

  9. Practice - Adding and Subtracting Sig Figs 2.099 g + 0.05681 g = 2.156 g 5.44 m – 2.6103 m = 2.83 m DON’T FORGET UNITS!!!!

  10. Multiplying and Dividing Sig Figs Your answer will be rounded to the same number of sig figs as the lowest number of sig figs by an original number. • 3.05 g / 8.5 mL • 3.05 g – 3 sig figs • 8.3 mL – 2 sig figs – answer gets rounded to 2 sig figs • 0.36 g/mL • Remember...treat units like algebra • Grams divided by milliliters = g/mL

  11. Multiplying and Dividing Sig Figs 2.4 g/mL x 15.82 mL 16.25 g / 5.1442 mL

  12. Multiplying and Dividing Sig Figs 2.4 g/mL x 15.82 mL = 38 g 16.25 g / 5.1442 mL = 3.159 g/mL

  13. This Week • Thursday – The Metric System (3.2) – HW 2-1 Due • Friday – Pd. 4 Only – Dimensional Analysis (3.3) – HW 2-2 Due • VIDEO: Drew Brees vs. Archer HW 2-1 Due Thursday

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