Chapter 1

1. Elements and Measurements Chapter 1

2. Chemistry and the Elements

3. Development of the Periodic Table Mendeleev’s Periodic Table (1871) Until the discovery of the proton, the elements were typically organized by increasing atomic weight. The modern organization is by increasing atomic number.

4. Periods: 7 horizontal rows. • Groups: 18 vertical columns. • International standard: 1-18 • US system: 1A-8A, 1B-8B

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

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

8. Some Chemical Properties of the Elements • Physical Properties: Characteristics that do notinvolve a change in a sample’s chemical makeup. • Chemical Properties: Characteristics that doinvolve a change in a sample’s chemical makeup.

9. Elements in the same group have the similar chemical properties

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

12. 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: Volume and Its Measurement

16. Derived Units: Measuring Volume

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

19. 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.

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

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 • What is the reading on the graduated cylinder?

24. 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. • 4.803 cm 4 sf

25. Accuracy, Precision, and Significant Figures • Rules for counting significant figures (left-to-right): • Zero at the beginning of a number are not significant (placeholders). 0.00661 g 3 sf or 6.61 x 10-3 g

26. Accuracy, Precision, and Significant Figures Rules for counting significant figures (left-to-right): • Zeros at the end of a number and after the decimal point are always significant. 55.220 K 5 sf

27. Accuracy, Precision, and Significant Figures • Zeros at the end of a number and after the decimal point may or may not be significant. 34,2000 ? SF

28. 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

29. Rounding 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

30. 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 • 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

31. Rounding Numbers • If the first digit you remove is 5 and there are more nonzero digits following, round up. 5.664 525 = 5.665 • If the digit you remove is a 5 with nothing following, round down. 5.664525 = 5.664 52

32. 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

33. 39.37 in 1 m 39.37 in 1 m Calculations: Converting from One Unit to Another Equivalent: 1 m = 39.37 in Conversion factor: or converts in to m converts m to in

34. 1 m 39.37 in Calculations: Converting from One Unit to Another E.g Convert 69.5 in to m 69.5 in x = 1.77 m starting quantity equivalent quantity conversion factor

35. Example • How many lb are in 35.5 kg? • Convert 2.00 in2 to cm2

36. Examples A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 lb aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans?

37. Example • The diameter of the nucleus of an atom is approximately 1 × 10- 3 pm. If 1 nm is equal to 10 Ångstroms, what is the diameter of the nucleus in Ångstroms?