Chapter 2

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. Stewarts height??? GO!!! Problem 2013, Robert Ayton. All rights reserved. www.mrayton.com

What information did you need to find out in yesterdays launch lab? What mattered? Bellwork What mattered??? Lip Height of one Cup (the final cup) How Tall is Mrs. Stewart. y = mx + b

My Height Lip 1 Cup Height # 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 32F 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 36C 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 places

3.4 + .28 + 35 = 4.6 x 103 - 3.9 x 102 ---------------------------- Practice Problems: Pg 53 #s 40 and 41 Adding and Subtracting Sig Figs 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 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 figures 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)

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