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Chapter 1

Chapter 1. Elements and Measurements. Chemistry and the Elements. Elements and the Periodic Table. Periods : 7 horizontal rows. Groups : 18 vertical columns. International standard: 1-18 US system: 1A-8A, 1B-8B. Elements and the Periodic Table. Main Groups columns 1A-2A (2 groups)

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Chapter 1

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  1. Chapter 1 Elements and Measurements

  2. Chemistry and the Elements

  3. Elements and the Periodic Table • Periods: 7 horizontal rows. • Groups: 18 vertical columns. • International standard: 1-18 • US system: 1A-8A, 1B-8B

  4. Elements and the Periodic Table • Main Groups • columns 1A-2A (2 groups) • columns 3A-8A (6 groups) • Transition Metals: 3B-2B (8 groups, 10 columns). • Inner Transition Metals: 14 groups between 3B and 4B. • lanthanides • actinides

  5. Elements and the Periodic Table Metals: Left side of the zigzag line in the periodic table (except for hydrogen). Nonmetals: Right side of the zigzag line in the periodic table. Semimetals (metalloids): Tend to lie along the zigzag line in the periodic table.

  6. Elements and the Periodic Table Alkali Metals

  7. Elements and the Periodic Table Alkaline Earth Metals

  8. Elements and the Periodic Table Halogens

  9. Elements and the Periodic Table Noble Gases

  10. Some Chemical Properties of the Elements • Intensive Properties: Independent of sample size. • temperature • melting point • Extensive Properties: Dependent on sample size. • length • volume

  11. Some Chemical Properties of the Elements • Physical Properties: Characteristics that do not involve a change in a sample’s chemical makeup. • Chemical Properties: Characteristics that do involve a change in a sample’s chemical makeup.

  12. Experimentation and Measurement Système Internationale d´Unités • All other units are derived from these fundamental units

  13. Measuring Mass • Mass: Amount of matter in an object. • Matter: Describes anything with a physical presence—anything you can touch, taste, or smell. • Weight: Measures the force with which gravity pulls on an object.

  14. Measuring Temperature TF = 1.8 TC + 32 TC = (TF – 32) 1.8 K = °C + 273.15

  15. Derived Units: Measuring Volume

  16. density = mass volume solids- cm3 liquids- mL gases- L Typical volume units Derived Units: Measuring Density

  17. Accuracy, Precision, and Significant Figures • Accuracy: How close to the true value a given measurement is. • Single measurement: percent error • Series of measurements: average • Precision: How well a number of independent measurements agree with each other. Characterized by the standard deviation.

  18. Accuracy, Precision, and Significant Figures Mass of a Tennis Ball good accuracy good precision

  19. Accuracy, Precision, and Significant Figures Mass of a Tennis Ball good accuracy poor precision

  20. Accuracy, Precision, and Significant Figures Mass of a Tennis Ball poor accuracy poor precision

  21. Accuracy, Precision, and Significant Figures • Significant figures: The number of meaningful digits in a measured or calculated quantity. They come from uncertainty in any measurement. • Generally the last digit in a reported measurement is uncertain (estimated). • Exact numbers and relationships (7 days in a week, 30 students in a class, etc.) effectively have an infinite number of significant figures.

  22. 0 1 2 3 4 Accuracy, Precision, and Significant Figures cm 1.7 cm < length < 1.8 cm length = 1.74 cm

  23. Accuracy, Precision, and Significant Figures Rules for counting significant figures (left-to-right): • Zeros in the middle of a number are like any other digit; they are always significant. • Zeros at the beginning of a number are not significant (placeholders). • Zeros at the end of a number and after the decimal point are always significant. • Zeros at the end of a number and after the decimal point may or may not be significant. • Use scientific notation

  24. Examples • 76.600 kg • 0.003400 mL • 18 students • 72,100 km

  25. 278 mi 11.70 gal Rounding Numbers Math rules for keeping track of significant figures: • Multiplication or division: The answer can’t have more significant figures than any of the original numbers. 3 SF = 23.8 mi/gal 4 SF 3 SF

  26. Rounding Numbers • Multiplication or division: The answer can’t have more significant figures than any of the original numbers. • Addition or subtraction: The answer can’t have more digits to the right of the decimal point than any of the original numbers. 3.18 2 decimal places 5 decimal places 2 decimal places 3.19 + 0.01315

  27. Rounding Numbers • Rules for rounding off numbers: • If the first digit you remove is less than 5, round down by dropping it and all following numbers. 5.664 525 = 5.66

  28. Rounding Numbers • 2. If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left. 5.664 525 = 5.7

  29. Rounding Numbers • If the first digit you remove is 5 and there are more nonzero digits following, round up. 5.664 525 = 5.665

  30. Rounding Numbers • If the digit you remove is a 5 with nothing following, round down. 5.664525 = 5.664 52

  31. Calculations: Converting from One Unit to Another • Dimensional analysis: A method that uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit. • Conversion factor: States the relationship between two different units. original quantity x conversion factor = equivalent quantity

  32. 39.37 in 1 m 39.37 in 1 m Calculations: Converting from One Unit to Another Relationship: 1 m = 39.37 in or Conversion factor: converts in to m converts m to in

  33. 1 m 39.37 in Calculations: Converting from One Unit to Another 69.5 in x = 1.77 m starting quantity equivalent quantity conversion factor

  34. Examples • Gemstones are weighed in carats, with 1 carat = 200 mg (exactly). What is the mass in gram of the Hope Diamond, the world’s largest blue diamond at 44.4 carats? • What is the volume in mm3 of this diamond if the density is 3.52 g/cm3 ?

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