Accuracy and Precision. Early muzzle loading rifles did not have adjustable sights and so the marksman had to know how his particular gun performed.

Slides:

Advertisements

Similar presentations

Errors in Measurements Class measurements for the density of gold (in g/mL) Group 117.8Group Group 218.0Group Group 317.9Group

Advertisements

Chemistry Question: What is the volume of water in the graduated cylinder in mL? How many sigfigs is this? How many L is this? Express this number in.

MEASUREMENT (A Quantitative Observation) MEASUREMENTS always have 2 things: Number & Unit All measurements have error in them! A measurement consists of.

Significant Figures. Purpose Significant figures are used with any measurement Significant figures are used with any measurement They tell you something.

Using Scientific Measurements.

Measurements: Every measurement has UNITS.

SIGNIFICANT FIGURES.

Significant Figures Part I: An Introduction. Objectives When you complete this presentation, you will be able to – distinguish between accuracy and precision.

Sig Figs meet Rounding!. In Science we take measurements, but those measurements are sometimes needed to find the values that we really want. For example:

UNIT 3 MEASUREMENT AND DATA PROCESSING

The Mathematics of Chemistry Significant Figures.

Making Measurements and Using Numbers The guide to lab calculations.

Introduction to Significant Figures &

Scientific Notation & Significant Figures in Measurement Dr. Sonali Saha Chemistry Honors Fall 2014.

Rules for Determining Significant Figures AP Chemistry U01L05.

Precision and Accuracy Uncertainty in 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.

Aim: How can we perform mathematical calculations with significant digits? Do Now: State how many sig. figs. are in each of the following: x 10.

Starter 1.How would you record the following measurements? How many sig figs? a.b. 2.Count the sig figs in the following measured values: a

Question 1 Rules for significant figures.

SIGNIFICANT FIGURES. ACCURACY VS. PRECISION  In labs, we are concerned by how “correct” our measurements are  They can be accurate and precise  Accurate:

Measurement book reference p Accuracy  The accuracy of the measurement refers to how close the measured value is to the true or accepted value.

Measurement book reference p Accuracy  The accuracy of the measurement refers to how close the measured value is to the true value.  For example,

Measuring and Units.

Significant Figure Notes With scientific notation too.

Using Scientific Measurements. Uncertainty in Measurements All measurements have uncertainty. 1.Measurements involve estimation by the person making the.

Chapter 2 Section 3 Using Scientific Measurements.

WARM UP Agenda Quiz Unit 1 Notes Unit 1-4 WS Unit 1 Density Work on online HW Homework Aug 28 – Online HW unit 1 Aug 31 - Test review WS Sept 2.

Ch.2 Measurements and Calculations

Scientists use math skills in collecting data and making measurements.

CHAPTER 3 NOTES Scientific Measurement. Measurement Qualitative measurements give results in descriptive, nonnumeric form. (Red balloon, tiny animal)

 Scientist use significant figures to determine how precise a measurement is  Significant digits in a measurement include all of the known digits.

Significant Figures A tutorial adapted from

How many significant digits? 5700 A.1 B.2 C.3 D.4.

Accuracy and Precision  Precision reflects the reproducibility of a given type of measurements (same answer) (same answer)  Accuracy reflects how close.

1 1-6 Working with Numbers. 2 Significant Digits (sig fig's) - certain digits and the estimated digit of a measurement. Significant Digits (sig fig's)

Scientific Notation & Significant Figures in Measurement.

Ch 5 How to take measurements and make proper calculations We will deal with many types of measurements and calculations throughout the year. The types.

Unit 3 Measurements & Calculations. Scientific Notation: Used to write very large or very small numbers Expressed as the product of 2 factors Mantissa:

Chemistry Chapter 2D Uncertainty in Measurement. Uncertainty  Represents how well a measurement was made  Science is ‘peer reviewed’  We don’t just.

Significant Figures Homework: Working with Numbers handout # 1 – 13 Significant Figures handout #

Accuracy vs. Precision. Calculations Involving Measured Quantities The accuracy of a measured quantity is based on the measurement tool. The last digit.

SOL Review 1.  Accuracy: measure of how close a measurement comes to the actual true value  Precision: measure how close a series of measurements are.

Accuracy, Precision and Significant Figures. Scientific Measurements All of the numbers of your certain of plus one more. –Here it would be 4.7x. –We.

Significant Figures. Rule #1 All non-zero numbers are significant 284 has ____ sig figs 123,456 has _____ sig figs.

Review Questions Write your answer, and nothing else, on the white board. Work together with people around you. Hold up your answer, but don’t say it too.

Making Measurements. SI system HW 1. A) g b) m. mm c) m 3 d) K e) m/s 2. A) 2g/cm 3 b) 25 kgm/s 2 (N) c. 13 m/s 2 3. A) mg b) 4.5 cm c) s.

Measurements and Mathematics in Chemistry

Learning Targets I can use correct numbers of significant figures and units in both measurements and calculations. I can accurately measure mass and volume.

How Reliable are Measurements?

Measurements and Significant Figures

Rules for Determining Significant figures

Introduction to Chemistry Part 2

Scientific Notation Scientific notation takes the form: M x 10n

And Calculating with Significant Digits

Significant Figures Any digit in a measurement that is known with certainty plus one final digit, which is somewhat uncertain or estimated.

Introduction to Significant Figures &

Analyzing Data Chemistry Chapter 2.

Review of Essential Skills:

Measurement book reference p

Which tool on the left could you be the most precise with?

Section 2.3 Uncertainty in Data

Significant Figures.

Significant Digits Calculations.

Using Scientific Measurements

The Mathematics of Chemistry

Which of these numbers has the most significant figures E 5

Calculation with Significant Figures

Lab Skills Intro.

Introduction to Significant Figures &

Presentation transcript:

Accuracy and Precision

Early muzzle loading rifles did not have adjustable sights and so the marksman had to know how his particular gun performed and then how to compensate. In muzzle loading rifle competition it is precision that is rewarded. An X marks the spot where the three bullets should “group”.

1234

1234 High precision, but low accuracy

1234 High precision, and high accuracy

1234 Low precision, but high accuracy

1234 Terrible precision, and lousy accuracy

1234 Precision deals with reproducibility. The closer the data, the better the precision.

1234 Accuracy is all about getting the right answer. The closer to the accepted value, the better the accuracy

In science we not only want measurements which are accurate, but we want measurements which are precise. In experiments where there is little variation between measurements of the same thing, there is good precision.

We judge the precision in measurements by the number of significant digits in the measurement.

The greater the number of significant digits, the more reproducible the measurements are.

We judge the precision in measurements by the number of significant digits in the measurement. The greater the number of significant digits, the more reproducible the measurements are cm is more precise and has more significant digits than 1.3 cm.

When we do calculations, the answer can be no more precision than the least precise factor in the calculation. D = m/V D = g / 15.5 cm 3 D = ??? How precisely should we express the density?

When we do calculations, the answer can be no more precision than the least precise factor in the calculation. D = m/V D = g / 15.5 cm 3 D = g/cm g/cm 3 has 4 significant digits, but the rules say that we can only have 3. 6 significant digits 3 significant digits

When we do calculations, the answer can be no more precision than the least precise factor in the calculation. D = m/V D = g / 15.5 cm 3 D = g/cm 3 We round the answer to 3 significant digits because 15.5 cm 3 has 3 significant digits, and it is the least precise factor. 6 significant digits 3 significant digits

Mercury in a graduated cylinder. What is the volume? ??? The graduations are precise to +/- 1 cm 3. Therefore, no decimal places.

Mercury in a graduated cylinder. What is the volume? 25 cm 3 The mass of the mercury is g. What is the value of the density?

D = m / V D = g / 25 cm 3 D = ??? 25 cm 3 How precisely can we express the density?

D = m / V D = g / 25 cm 3 D = g/cm 3 25 cm 3 The calculator says But! The answer can only be expressed to two significant digits.

D = m / V D = g / 25 cm 3 D = 14 g/cm 3 25 cm 3 Round the answer to two significant digits.

Mike Jones Pisgah High School Canton NC Last revised 04/04/12 C2012 – All rights reserved.