Do Now Activity Sit down quietly in your assigned seat and begin writing 3 to 4 sentences about what is an atom and how atoms relate to elements. (8 minutes to complete this) This should be written in your notebook for this class or loose leaf paper if you do not have a note book yet. LecturePLUS Timberlake1

2 Chemistry Luskin Academy Mr. Berlin Introduction to Chemistry Measurements Significant figures The Atom Atomic Number and Mass Number Isotopes

Measurements Measured Numbers and Significant Figures

Measured Numbers When you use a measuring tool is used to determine a quantity such as your height or weight. These type of numbers are called simply measured numbers.

Reading a Meterstick. l I.... I 3....I.... I 4.. cm First digit (known)= 2 2.?? cm Second digit (known)= ? cm Third digit (estimated) between Length reported=2.75 cm or2.76 cm or2.77 cm

Known + Estimated Digits Known digits 2 and 7 are 100% certain The third digit 6 is estimated (uncertain) In the reported length, all three digits (2.76 cm) are significant including the estimated one

Learning Check. l I.... I 9....I.... I 10.. cm What is the length of the line? 1) 9.3 cm 2) 9.32 cm 3) 9.33 cm How your answer compare with your neighbor ’ s answer? Why or why not?

Solution. l I.... I 9....I.... I 10.. cm Estimate to the hundreth ’ s place (0.01 cm) 2) 9.32 cm 3) 9.33 cm The estimated digit may be slightly different. Both readings are acceptable.

Learning Check l I.... I 6....I.... I 7.. cm What is the length of the line? 1) 6.0 cm 2) 6.09 cm 3) 6.60 cm

Solution l I.... I 6....I.... I 7.. cm Estimate to the hundreth ’ s place (0.01 cm). The reading is between 6.0 and 6.1. You may have estimated 6.07 cm as well. 2) 6.09 cm

Zero as a Measured Number. l I.... I I.... I 5.. cm What is the length of the line? First digit 4.?? cm Second digit 4.6? cm Last (estimated) digit is 4.60 cm (not to the left or right of.5)

Exact Numbers Obtained when you count objects 2 soccer balls 1 watch 4 pizzas Obtained from a defined relationship 1 foot = 12 inches 1 meters = 100 cm Not obtained with measuring tools

Learning Check A. Exact numbers are obtained by 1. measuring 2. counting 3. definition B. Measured numbers are obtained by 1. measuring 2. counting 3. definition

Solution A. Exact numbers are obtained by 2. counting 3. definition B. Measured numbers are obtained by 1. Using a measuring tool

Learning Check Classify each of the following as an exact (1) or a measured (2) number. A.___Gold melts at 1064°C B.___1 yard = 3 feet C.___A red blood cell with diameter 6 x cm D.___There were 6 hats on the shelf E.___A can of soda contains 355 mL of soda

Solution Classify each of the following as an exact (1) or a measured(2) number. Give reason. A. 2 Requires a thermometer(measuring tool) B. 1 From a definition in U.S. system C. 2 Need measuring tool to determine D. 1 Counted the hats E. 2 Measured

Timberlake lecture plus17 Measurements Significant Figures in Calculations

Timberlake lecture plus18 Significant Figures in Measurement The numbers reported in a measurement are limited by the measuring tool Significant figures in a measurement include the known digits plus one estimated digit

Timberlake lecture plus19 Counting Significant Figures Number of Significant Figures cm4 5.6 ft lb___ m___ Complete: All non-zero digits in a measured number are (significant or not significant).

Timberlake lecture plus20 Leading Zeros Number of Significant Figures mm oz lb____ mL ____ Complete: Leading zeros in decimal numbers are (significant or not significant).

Timberlake lecture plus21 Sandwiched Zeros Number of Significant Figures 50.8 mm min lb____ m ____ Complete: Zeros between nonzero numbers are (significant or not significant).

Timberlake lecture plus22 Trailing Zeros Number of Significant Figures 25,000 in yr1 48,600 gal3 25,005,000 g ____ Complete: Trailing zeros in numbers without decimals are (significant or not significant) if they are serving as place holders.

Timberlake lecture plus23 Learning Check A. Which answers contain 3 significant figures? 1) ) ) 4760 B. All the zeros are significant in 1) ) ) x 10 3 C. 534,675 rounded to 3 significant figures is 1) 535 2) 535,000 3) 5.35 x 10 5

Timberlake lecture plus24 Solution A. Which answers contain 3 significant figures? 2) ) 4760 B. All the zeros are significant in 2) ) x 10 3 C. 534,675 rounded to 3 significant figures is 2) 535,000 3) 5.35 x 10 5

Timberlake lecture plus25 Learning Check In which set(s) do both numbers contain the same number of significant figures? 1) 22.0 and ) and 40 3) and 150,000

Timberlake lecture plus26 Solution In which set(s) do both numbers contain the same number of significant figures? 3) and 150,000

Timberlake lecture plus27 State the number of significant figures in each of the following: A m B L C g D m E. 2,080,000 bees Learning Check SF3

Timberlake lecture plus28 A m2 B L4 C g1 D m 3 E. 2,080,000 bees3 Solution

Exit Question…. Remain in your seats until the bell rings. “What are significant figures in your own words? How are zeros counted in regards to significant figures? What did you learn about measuring tools and how accurate they can be?” LecturePLUS Timberlake29

Do Now activity…. Answer the following: How many significant figures in; a) cm, b) 4.50 cm, c) 7600 feet, d) mm, e) 550 ml, f) km Which would be the proper tool to measure 4.5 ml of water; a) 100 ml graduated cylinder, b) 10 ml graduated cylinder, 10 ml beaker For measuring a room in feet a) meter stick, b) tape measure, c) ruler 30

Timberlake lecture plus31 Significant Numbers in Calculations A calculated answer cannot be more precise than the measuring tool. A calculated answer must match the least precise measurement. Significant figures are needed for final answers from 1) adding or subtracting 2) multiplying or dividing

Timberlake lecture plus32 Adding and Subtracting The answer has the same number of decimal places as the measurement with the fewest decimal places one decimal place two decimal places answer 26.5 one decimal place

Timberlake lecture plus33 Learning Check In each calculation, round the answer to the correct number of significant figures. A = 1) ) ) 257 B = 1) ) ) 40.7

Timberlake lecture plus34 Solution A = 2) B = 3) 40.7

Timberlake lecture plus35 Multiplying and Dividing Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures.

Timberlake lecture plus36 Learning Check A X 4.2 = 1) 9 2) 9.2 3) B ÷ 0.07 = 1) ) 62 3) 60 C X = X ) 11.32) 11 3) 0.041

Timberlake lecture plus37 Solution A X 4.2 = 2) 9.2 B ÷ 0.07 = 3) 60 C.2.54 X = 2) X Continuous calculator operation = 2.54 x   0.060

Precision, accuracy and measurements LecturePLUS Timberlake38

39 Atomic Theory Atoms are building blocks of elements. Remember how tiny an atom is. Billions of atoms are on a pencil tip. Similar (same) atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds (Molecules)

40 Subatomic Particles: atoms are made of smaller particles. ParticleSymbol Charge Relative Mass Electron e Proton p Neutron n0 1

41 Location of Subatomic Particles Atom size about cm Neutron (0) Proton (+ ) Electron (-)

Bohr Atomic Model LecturePLUS Timberlake42

Modern Atomic Model LecturePLUS Timberlake43

Atomic model overview LecturePLUS Timberlake44

LecturePLUS Timberlake45 Atomic Number Atomic number is the number of protons in an atom (the positive sub-atomic particle)

LecturePLUS Timberlake46 Atomic Number - The periodic table is arranged by the atomic number. 11 Na Atomic Number Symbol

LecturePLUS Timberlake47 All atoms of an element have the same number of protons 11 Na 11 protons Sodium

LecturePLUS Timberlake48

LecturePLUS Timberlake49

Periodic Table LecturePLUS Timberlake50 Zx0tv6dQ NlVM5YBswhttps:// NlVM5YBsw

LecturePLUS Timberlake51

LecturePLUS Timberlake52 Learning Check State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons

LecturePLUS Timberlake53 Solution State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons

LecturePLUS Timberlake54 Mass Number Counts the number of protons and neutrons in an atom

LecturePLUS Timberlake55 Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 Na sodium-23 atomic number 11

LecturePLUS Timberlake56 Number of Electrons An atom is neutral on the Periodic Table The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons

LecturePLUS Timberlake57 Subatomic Particles in Some Atoms O P Zn p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e -

LecturePLUS Timberlake58 Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37

LecturePLUS Timberlake59 Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 13 C 14 C #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______

LecturePLUS Timberlake60 Solution 12 C 13 C 14 C #p #n #e 6 6 6

LecturePLUS Timberlake61 Learning Check An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 353) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 372) 653) 67

LecturePLUS Timberlake62 Solution An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 30 B.Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

LecturePLUS Timberlake63 Learning Check Write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - ___________ B.17p +, 20n, 17e - ___________ C. 47p +, 60 n, 47 e - ___________

LecturePLUS Timberlake64 Solution 16 O A. 8 p +, 8 n, 8 e - 8 B.17p +, 20n, 17e - 37 Cl 17 C. 47p +, 60 n, 47 e Ag 47

LecturePLUS Timberlake65 Atomic Mass on the Periodic Table 11 Na Atomic Number Symbol Atomic Mass

LecturePLUS Timberlake66 Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.

LecturePLUS Timberlake67 Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = x 24.5 =

Exit Question…. What is a proton? What is a neutron? What is an electron? What is atomic number? How is the periodic table arranged? Once you are done remain in your seats and turn in your exit question as you leave the classroom. LecturePLUS Timberlake68