Chapter 2 Section 3 Using Scientific Measurements Lesson Starter • Look at the specifications for electronic balances. How do the instruments vary in precision? • Discuss.
Download ReportTranscript Chapter 2 Section 3 Using Scientific Measurements Lesson Starter • Look at the specifications for electronic balances. How do the instruments vary in precision? • Discuss.
Chapter 2 Section 3 Using Scientific Measurements Lesson Starter • Look at the specifications for electronic balances. How do the instruments vary in precision?
• Discuss using a beaker to measure volume versus using a graduated cylinder. Which is more precise?
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Objectives • **Distinguish between accuracy and precision.
• **Determine the number of significant figures in measurements.
• Perform mathematical operations involving significant figures.
• Convert measurements into scientific notation.
• Distinguish between inversely and directly proportional relationships.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
2.3
Measurements and Their Uncertainty On January 4, 2004, the Mars Exploration Rover Spirit landed on Mars. Each day of its mission, Spirit recorded measurements for analysis. In the chemistry laboratory, you must strive for accuracy and precision in your measurements. (In August 2012, a new rover landed on Mars to collect data.) © Copyright Pearson Prentice Hall 3 Slide of 48 End Show
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error Accuracy, Precision, and Error How do you evaluate accuracy and precision?
© Copyright Pearson Prentice Hall 4 Slide of 48 End Show
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error Accuracy and Precision • Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured. • Precision is a measure of how close a series of measurements are to one another.
5 Slide of 48 End Show © Copyright Pearson Prentice Hall
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error To evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To evaluate the precision of a measurement, you must compare the values of two or more repeated measurements.
6 Slide of 48 End Show © Copyright Pearson Prentice Hall
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error © Copyright Pearson Prentice Hall 7 Slide of 48 End Show
Chapter 2 Section 3 Using Scientific Measurements Accuracy and Precision
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Visual Concepts Accuracy and Precision Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/st udent/ch02/sec03/vc00/hc602_03_v00fs.h
tm
Copyright © by Holt, Rinehart and Winston. All rights reserved.
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error Just because a measuring device works, you cannot assume it is accurate. The scale below has not been properly zeroed, so the reading obtained for the person’s weight is inaccurate.
© Copyright Pearson Prentice Hall 10 Slide of 48 End Show
2.3
Measurements and Their Uncertainty > Accuracy, Precision, and Error Determining Error • The accepted value is the correct value based on reliable references. • The experimental value is the value measured in the lab. • The difference between the experimental value and the accepted value is called the error. 11 Slide of 48 End Show © Copyright Pearson Prentice Hall
Chapter 2 Section 3 Using Scientific Measurements Accuracy and Precision, continued Percentage Error • Percentage error is calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100.
Percentage error = Value experimental -Value accepted Value accepted
100
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Percentage Error Visual Concept Click below for Visual Concept Click for Visual Concept on Percent Error
Copyright © by Holt, Rinehart and Winston. All rights reserved.
PERCENT ERROR PROBLEM ACTIVITY CLICK HERE FOR PERCENT ERROR PROBLEM ACTIVITY
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Accuracy and Precision, continued Problem Example - RECORD in notes before checking.
A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement?
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Accuracy and Precision, continued Sample Problem C Solution
Percentage error = Value experimental -Value accepted Value accepted
100
1.40
g / mL - 1.30
g / mL 1.30
g / mL 100 7.7%
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Accuracy and Precision, continued Error in Measurement • Some error or uncertainty always exists in any measurement.
• • • skill of the measurer conditions of measurement measuring instruments
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Significant Figures • Significant figures in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.
• The term significant does not mean certain.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements
Sig. figs. in a measurement include the known digits plus a final estimated digit
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Visual Concepts Significant Figures Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/student/ Visual Concept ch02/sec03/vc02/hc602_03_v02fs.htm
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Significant Figures, continued Determining the Number of Significant Figures
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Visual Concepts Rules for Determining Significant Zeros Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809x/student/ch0 Visual Concept 2/sec03/vc03/hc602_03_v03fs.htm
Copyright © by Holt, Rinehart and Winston. All rights reserved.
C. Significant Figures
Counting Sig Fig Examples 4 sig figs 3 sig figs 3 sig figs
C. Johannesson
2 sig figs
Chapter 2 Section 3 Using Scientific Measurements Significant Figures, continued Sample Problem D How many significant figures are in each of the following measurements?
a. 28.6 g b. 3440. cm c. 910 m d. 0.046 04 L e. 0.006 700 0 kg
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Significant Figures, continued Sample Problem D Solution a. 28.6 g There are no zeros, so all three digits are significant.
b. 3440. cm By rule 4, the zero is significant because it is immediately followed by a decimal point; there are 4 significant figures.
c. 910 m By rule 4, the zero is not significant; there are 2 significant figures.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Significant Figures, continued Sample Problem D Solution, continued d. 0.046 04 L By rule 2, the first two zeros are not significant; by rule 1, the third zero is significant; there are 4 significant figures.
e. 0.006 700 0 kg By rule 2, the first three zeros are not significant; by rule 3, the last three zeros are significant; there are 5 significant figures.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
SIG. FIG. PRACTICE QUESTIONS
Copyright © by Holt, Rinehart and Winston. All rights reserved.
SIG. FIG. ANSWERS - CHECK WORK
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Section 3 Using Scientific Measurements Significant Figures, continued Rounding
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 2 Visual Concepts Rules for Rounding Numbers Click below to watch the Visual Concept.
http://my.hrw.com/sh/hc6_003036809 x/student/ch02/sec03/vc04/hc602_03_ v04fs.htm
Copyright © by Holt, Rinehart and Winston. All rights reserved.
C. Significant Figures
Calculating with Sig Figs Multiply/Divide - The # with the fewest sig figs determines the # of sig figs in the answer.
(13.91g/cm
3
)(23.3cm
3
) = 324.103g
4 SF 3 SF 3 SF
324 g
C. Johannesson
C. Significant Figures
Calculating with Sig Figs (con’t) Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer.
7.8 mL
C. Johannesson
350 g
C. Significant Figures
Calculating with Sig Figs (con’t) Exact Numbers do not limit the # of sig figs in the answer.
Counting numbers: 12 students Exact conversions: 1 m = 100 cm “1” in any conversion: 1 in = 2.54 cm C. Johannesson
C. Significant Figures
Practice Problems
f). (15.30 g) ÷ (6.4 mL)
4 SF 2 SF
= 2.390625 g/mL
2.4 g/mL
2 SF
g). 18.9 g - 0.84 g 18.06 g
18.1 g
C. Johannesson
D. Scientific Notation
65,000 kg
6.5 × 10
4
kg
Converting into Sci. Notation: Move decimal until there’s 1 digit to its left. Places moved = exponent.
Large # (>1) positive exponent Small # (<1) negative exponent
D. Scientific Notation
h.
g Practice Problems 2,400,000 2.4
10
6
g 2.56
10
-3
kg
i. 0.00256 kg
j.
7
10
-5
0.00007 km 62,000 mm
C. Johannesson
km
D. Scientific Notation
Calculating with Sci. Notation (5.44 × 10 7 g) ÷ (8.1 × 10 4 mol) = Type on your calculator: 5.44
EXP EE 7 ÷ 8.1
EXP EE 4 EXE ENTER = 671.6049383 = 670 g/mol = 6.7 × 10 2 C. Johannesson g/mol
Stop here and play BINGO GAME ACTIVITY HW: Study Guide Questions due on Friday.
Get out a sheet of paper and make a 5 x 5 grid. (5 rows and 5 columns)
Copyright © by Holt, Rinehart and Winston. All rights reserved.
E. Proportions
Direct Proportion y Inverse Proportion C. Johannesson y x x
Section Assessment Assess students’ understanding of the concepts in Section 2.3.
Continue to: Launch: -or Section Quiz Slide of 48 End Show © Copyright Pearson Prentice Hall
2.3 Check up Section Quiz 1. In which of the following expressions is the number on the left NOT equal to the number on the right?
a. 0.00456 10 –8 = 4.56 10 –11 b. 454 10 –8 = 4.54 10 –6 c. 842.6 10 4 = 8.426 10 6 d. 0.00452 10 6 = 4.52 10 9 Slide of 27 End Show © Copyright Pearson Prentice Hall
2.3 Section Quiz 2. Which set of measurements of a 2.00-g standard is the most precise?
a. 2.00 g, 2.01 g, 1.98 g b. 2.10 g, 2.00 g, 2.20 g c. 2.02 g, 2.03 g, 2.04 g d. 1.50 g, 2.00 g, 2.50 g Slide of 27 End Show © Copyright Pearson Prentice Hall
2.3 Section Quiz 3. A student reports the volume of a liquid as 0.0130 L. How many significant figures are in this measurement?
a. 2 b. 3 c. 4 d. 5 Slide of 27 End Show © Copyright Pearson Prentice Hall
Online Self-Check Quiz Complete the online 2.3 Quiz and record answers. Ask if you have any questions about your answers. Click here for Section 2.3 QUIZ (10 questions) Some of these are challenging. Ask if you miss and need help understanding. It is imperative you get help when something doesn’t make sense to be successful.
You must be in the “Play mode” for the slideshow for hyperlink to work.
Slide of 25 End Show © Copyright Pearson Prentice Hall
VIDEOS FOR ADDITIONAL INSTRUCTION Additional Videos for Section 2.3 Using Scientific Measurements (4 videoclips) • Direct Variation (1:44) • Inverse Variation (2:12) • Significant Figures (6:04) • Scientific Notation (2:26) © Copyright Pearson Prentice Hall Slide of 27 End Show
VIDEOS FOR ADDITIONAL INSTRUCTION Additional Videos for Section 2.3 Using Scientific Measurements (4 videoclips) • Direct Variation (1:44) • Inverse Variation (2:12) • Significant Figures (6:04) • Scientific Notation (2:26) © Copyright Pearson Prentice Hall Slide of 27 End Show
SCI LINKS FOR CHAPTER Additional Student SCI LINKS for CHAPTER 2 The NSTA-sponsored SciLinks Web site contains links to accurate and up to-date science information on the Internet. Just click on the button below to go to the SciLinks site at www.scilinks.org
and log in. Then, type in the SciLinks code for the topic you want to research. The following is a list of the SciLinks codes for this chapter.
Chapter 2: Measurements and Calculations Topic:
Scientific Methods
SciLinks code:
HC61359 © Copyright Pearson Prentice Hall Slide of 27 End Show
End of Chapter 2.3 Show
Copyright © by Holt, Rinehart and Winston. All rights reserved.