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Chapter 2 Analyzing Data • Make a new section in your table of contents – Chapter 2: Analyzing Data • Do not forget page numbers • Beginning, ending, and throughout book • Go to first blank page and write chapter 2 across it Bellwork • Chapter Essential Question: • How do scientists analyze data in order to determine how matter interacts? • Lesson Essential Questions: • Why do chemists use an international system of measurement? • Why do measurements contain uncertainties and how can we counteract these? Next Page – Copy Down • Essential questions from Chapters 1, 2, and 3 will be due on Exam day. Reminder!!! • Four column definition activity • Word, Definition, Your Definition, Picture/Example • Words • • • • • • Accuracy Density Percent Error Precision Scientific Notation Significant Figures • Conversions • Base Units • SI units Chapter 2 Word Study Guide •Read Chapter 2 • Complete the Chapter 2 Outline • Do not just DEFINE words • Give complete explanations Bellwork/Homework • How many Styrofoam cups equal Mrs. Stewart’s height??? GO!!! Problem © 2013, Robert Ayton. All rights reserved. www.mrayton.com • What information did you need to find out in yesterday’s launch lab? • What mattered? Bellwork • What mattered??? • Lip • Height of one Cup (the final cup) • How Tall is Mrs. Stewart. y = mx + b 1 Cup Height My Height Lip # of Cups Styrofoam Cup Lab © 2013, Robert Ayton. All rights reserved. www.mrayton.com • What was the benefits of this lab? • • • • • Measuring Forming Scientific Questions Data Collections Communication Connecting to Other Subject Areas Styrofoam Cup Lab © 2013, Robert Ayton. All rights reserved. www.mrayton.com • In your journal, answer the following questions • What are the base units for Time, Length, Mass, Temperature, and Volume. • Discuss what density is, and how do you measure it. • How do you convert between two different units. Metric Units • 2.34g cg • 456 dL hL Lets Complete a couple examples • • • • • 0.026L mL 832ks hs 34,600 m km 398.6dg dag WHEN I TELL YOU!!!! Get with your shoulder partner and discuss your answers. Convert the following Numbers • Identify the equations used to convert between °C and K. As well as between °C and °F. • Convert the following • 365 K °C • 32°F °C Journal • When a piece of aluminum with a density of 2.7 g/mL is placed in a 25mL graduated cylinder that contains 10.5 mL of water, the water level rises to 13.5 mL. What is the mass of the aluminum? Density • Complete problems 1-3 on page 38 • Get with your shoulder partner and discuss your answers as well as the process. Practice Problems • Is used to express any number as a number between 1 and 10 multiplied by 10 raised to a power. Scientific Notation • Page 41 #’s 11 and 12 • Get with your shoulder partner and discuss your answers. • We will go over them as a class! Practice Using Scientific Notation • If a piece of metal has a density of 6.23 g/cm3 and a mass of 12.4 g, what is the volume of the metal? • Convert the following units • 0.36 L mL • 32300 dm km • 43.6 hg cg • Put in Scientific Notation • 0.00034 km • 63000000 mg • Write in standard notation • 3.6 x 105 • 6.34 x 10-7 Understanding Check • Step 1: Notice if the powers of 10 are the same • If they are bring straight down and add or subtract front numbers like normal • If not, move to step 2 • Step 2: Identify the highest power of 10 and keep it the same • Step 3: Make the power of 10 the same as the higher number by moving the decimal left the correct number of spaces. • Step 4: bring the power of 10 down, and then add or subtract front numbers like normal Adding and Subtracting Scientific Notation Adding Subtracting 1. 2.3 x 103 +9.8 x 102 1. 7.3 x 104 - 2.6 x 106 -------------------------- -------------------------- 2. 3.6 x 105 + 4.2 x 106 2. 8.1 x 102 - 5.3 x 104 --------------------------- --------------------------- Adding and Subtracting Examples • MOVE DECIMAL TO MAKE THE POWER OF 10 THE SAME!!! • Go with the highest exponent • Practice Problems pg 42 • 13cd and 14cd Bellwork: Adding and Subtracting Scientific Notation • Turn in weekend homework problems • Review adding and subtracting scientific notation with your shoulder partner. • (8.6 x 105) – (2.2 x 103) • (7.2 x 10-1 kg) + (6.8 x 10-1 g) in grams Bellwork • Step 1: Identify whether you are multiplying or dividing • Step 2: if multiplying, add exponents. If dividing, subtract exponents. • Step 3: Multiply or divide front numbers like normal • Step 4: Make sure your final answer is in correct scientific notation. Multiplying and dividing scientific Notation Multiplying Dividing 1. 2.3 x 105 x1.6 x 103 1. 9.72 x 108 / 1.3 x 105 -------------------------- ------------------------- 2. 6.7 x 102 x 5.2 x 103 2. 5.2 x 104 / 3.6 x 108 -------------------------- ------------------------ Multiplying and Dividing Examples • IF MULTIPLYING, ADD powers of 10. • If DIVIDING, SUBTRACT powers of 10. • Practice Problems pg 43 • 15bd and 16bd Multiplying and Dividing Scientific Notation • Complete the following problems • • • • (2.3 x 102) – (9.2 x 103) (3.4 x 10-3 kg) + (6.8 x 10-1 kg) (2.35 x 103) x (6.00 x 105) (4.3 x 102)/(7.38 x 104) Review Accuracy Data • The true value is .5g • The students experimental values are: • • • • Accuracy .51g .49g .5g .52g Precision Data • The true value is .5g • The students experimental values are: • • • • Precision .8g .81g .79g .79g Accuracy vs. Precision • Three Key Components 1. Accepted Value 1. A value determined correct through mathematical calculations 2. Experimental Value 1. A value determined through experimentation (your value) 3. Error 1. How far the experimental value is from the accepted value. Error • Joshua uses his thermometer and finds the boiling point of ethyl alcohol to be 75oC. He looks in a reference book and finds that the actual boiling point of ethyl alcohol is 80oC. • What is his error? Example: Error=Experimental value-accepted value • Equation on page 48 • Percent error = ( error /accepted value) x 100 • Percent error expresses error as a percentage of the accepted value • Most commonly used error expression • Must have: error and accepted value to calculate • Example • The density of water at 4oC is known to be 1.00 g/mL. Kayla experimentally found the density of water to be 1.075 g/mL. What is her percent error? Percent Error • You may work with your shoulder partner • Examples page 49 • 32-34 Practice Problems • Rules • Every NON ZERO digit is significant • Zeros to the LEFT of the first non-zero digit is NEVER significant • Zeros in the MIDDLE of two non-zero digits are ALWAYS significant • Zeros to the Right of the LAST non-zero digit are SOMETIMES significant • If you see a decimal = YES! • If you DO NOT see a decimal = NO! • Counting numbers and ratios/conversions have an infinite number of significant figures. Copy: Significant Figures • Examples: • 1234 = 4 significant figures • 2.34 = 3 significant figures • 14,567 = 5 significant figures • How many significant figures in the following numbers? • 54 • 3.4568 Rule 1: Every NON ZERO digit is significant • Steps • Find 1st non-zero digit • Cross out all zeros in front of it • Examples • 0.00023 = 2 significant figures • 0.6789 = 4 significant figures • Practice • 0.344 • 0.000007 Rule 2: Zeros to the LEFT of the first non-zero digit is NEVER significant • This means all zeros surrounded by non-zero digits are ALWAYS counted as significant. • Example: • 43201 = 5 significant figures • 2001 = 4 significant figures • 403050708 = 9 significant figures • Practice Problems • 600045 • 902 Rule 3: Zeros in the MIDDLE of two nonzero digits are ALWAYS significant • Steps • Identify last non-zero digit • If there are zeros to the right, then look for a decimal somewhere in the number • If you see a decimal = YES!! • If no decimal = NO! • Example • 3.4000 = 5 significant figures (decimal) • 34000 = 2 significant figures (no decimal) • Practice Problems • 654.000 • 3340. • 200 Rule 4: Zeros to the Right of the LAST nonzero digit are SOMETIMES significant • If you are counting an object there are infinite significant figures • Ex: 8 computers = infinite significant figures • Ex: 26 students = infinite significant figures • If you have a conversion or ratio the are infinite significant figures • Ex: 1000mm = 1m = infinite • Ex: 12 eggs = 1 dz Rule 5: Counting numbers and ratios/conversions have an infinite number of significant figures. • • • • All non zeros are significant Left zeros = never Middle Zeros = Always Right Zeros = Only if there is a decimal Key Points • Determine the number of significant figures in the following measured values • • • • • 0.0546 298.206 102000 0.003145 7.847000 Examples • Pg 51 #’s 35-37 Practice Problems • Convert • 40g mg • .00034 km cm • 36°C K • Scientific Notation • 0.0000067 • (2.4 x 103) + (3.6 x 102) • (3.5 x 106) / (1.7 x 108) • Accuracy vs. Precision • Explain the difference between accuracy and precision • Error • A student completed their experiment and wanted to calculate their percent error. The teacher explained that the precipitate should have had a mass of 4.8g. The student calculated a mass of 3.4g. Help the student calculate their percent error! Bellwork • Round to the lowest amount of decimal • Examples • 3.4 + .28 + 35 = • 4.6 x 103 - 3.9 x 102 ---------------------------- • Practice Problems: Pg 53 #’s 40 and 41 Adding and Subtracting Sig Fig’s places • Chemistry Handbook •Page 18 #’s 24a-d and 25 ab •Separate sheet of paper H.W. Practice problems • Round to the lowest number of significant figures • Examples • 1.3 x 0.2 x 3.26 = • 3.46 x 103 / .60 x 102 --------------------------- • Practice Problems: 42ab, 43cd, 44 (pg 54) Multiplying and Dividing Sig Figs • Write down all the rules for SIGNIFICANT FIGURES! • How do you round when you add and subtract? • How do you round when you multiply and divide? Journal Entry – 5 min 1. With your shoulder partner, complete the worksheet in your COMPOSITION BOOK. 2. When told to do so, you will get with another partner and come up with a consensus on a separate sheet of paper for all answers 3. Turn in consensus paper for a GRADE Significant Figures Worksheet • TURN IN EQs RIGHT NOW!!!! • Get with your shoulder partner and continue working on the worksheet • You have about 15 minutes • Test you need • Two sheets of paper • Pencil • Calculator Bellwork • 32 (pg49), 35ac,36ac, 37 (pg 51), 38ab, 39ab, 40, 41 (pg53),42ab,43ab,44 (pg54) Complete Practice Problems (Shoulder Partner)