Accuracy vs. Precision Measurements need to accurate & precise. Accurate -(correct) the measurement is close to the true value. Precise –(reproducible)

Slides:



Advertisements
Similar presentations
Chapter 2 – Scientific Measurement
Advertisements

Physics Rules for using Significant Figures. Rules for Averaging Trials Determine the average of the trials using a calculator Determine the uncertainty.
S IGNIFICANT F IGURES. Significant figures Numbers known to have some degree of reliability Critical when reporting scientific data Tell accuracy of measurement.
MEASUREMENT (A Quantitative Observation) MEASUREMENTS always have 2 things: Number & Unit All measurements have error in them! A measurement consists of.
Uncertainty in Measurements
Measurements: Every measurement has UNITS.
Do Now The speed of light is 300,000,000 m/s
POWERPOINT THE SECOND In which you will learn about: Scientific notation +/-/x/÷ with sig figs Rounding.
Using and Expressing Measurements
Measurements: Every measurement has UNITS.
Scientific Notation Converting into Sci. Notation: –Move decimal until there’s 1 digit to its left. Places moved = exponent. –Large # (>1)  positive.
I II III I. Using Measurements CH. 2 - MEASUREMENT.
Measurement book reference p Accuracy  The accuracy of the measurement refers to how close the measured value is to the true or accepted value.
The Importance of measurement Scientific Notation.
Scientific Measurement. Measurements are fundamental to the experimental sciences.  Measurement: A quantity that has both a number and a unit.  Scientific.
Calculations Notes. Multiplication and Division Number of the sig. figs. is the result of the measurement with the smallest number of sig. figs. (least.
I II III I. Using Measurements CH. 2 - MEASUREMENT.
SIGNIFICANT FIGURES. What are they?  It is important to be honest when reporting a measurement, so that it does not appear to be more accurate than the.
Significant Figures. What is a significant figure? The precision of measurements are indicated based on the number of digits reported. Significant figures.
I II III I. Using Measurements (p. 8-15) CH MEASUREMENT.
Mastery of Significant Figures, Scientific Notation and Calculations Goal: Students will demonstrate success in identifying the number of significant figures.
Scientific Notation and Significant Figures. Going from scientific notation to standard number form. ◦A positive exponent means move the decimal to the.
What is the difference between accuracy and precision? Good precision Low accuracy = average position Low precision High accuracy.
“Scientific Measurement”. Measurements and Their Uncertainty OBJECTIVES: Convert measurements to scientific notation.
Chapter 2 - Section 3 Suggested Reading Pages Using Scientific Measurements.
Uncertainty and Measurements There are errors associated with any measurement. Random error Random error – These errors can be caused by a variety of sources:
Accuracy & Precision & Significant Digits. Accuracy & Precision What’s difference? Accuracy – The closeness of the average of a set of measurements to.
I II III Using Measurements MEASUREMENT. Accuracy vs. Precision  Accuracy - how close a measurement is to the accepted value  Precision - how close.
Significant Figures. Rule 1: Digits other than zero are significant 96 g = 2 Sig Figs 152 g = __________ Sig Figs 61.4 g = 3 Sig Figs g = __________.
Units of Measurement SI units (Systeme Internationale d’Unites) were developed so that scientists could duplicate and communicate their work. Base UnitsDerived.
SCIENTIFIC NOTATION 5.67 x 10 5 –Coefficient –Base –Exponent 1. The coefficient must be greater than or equal to 1 and less than The base must be.
Chapter 2 Sec 2.3 Scientific Measurement. Vocabulary 14. accuracy 15. precision 16. percent error 17. significant figures 18. scientific notation 19.
DAY 14 DAY 14 – Sig figs / Scientific Notation Day 15 - Density LAB Day 16 – Measurement / sig fig quiz.
SIGNIFICANT digits (a.k.a. Sig Figs). What are sig figs?  It is important to be honest when reporting a measurement, so that it does not appear to be.
Mastery of Significant Figures, Scientific Notation and Calculations Goal: Students will demonstrate success in identifying the number of significant figures.
I. Using Measurements (p )
Significant Figures. Rule 1: Nonzero numbers are always significant. Ex.) 72.3 has 3 sig figs.
DAY 14 DAY 14 – Sig figs / Scientific Notation Day 15 - Density LAB Day 16 – Measurement / sig fig quiz.
Units 1: Introduction to Chemistry
III. Using Measurements (p )
Unit 1 Chapter 2 Pages
Measurement: Significant Figures
Scientific Notation and Significant Figures
CH. 2 - MEASUREMENT I. Using Measurements.
Significant Figures
I. Using Measurements (p )
-Accuracy & Precision - Significant Digits -Scientific Notation
Lesson 2 – Sci. Notation, Accuracy, and Significant Figures
Chapter 3 Scientific Measurement 3.1 Using and Expressing Measurements
Chapter 3 Scientific Measurement 3.1 Using and Expressing Measurements
Section 3-2 Uncertainty in Measurements
Measurements & Calculations
Measurement book reference p
Chapter 3 Scientific Measurement 3.1 Using and Expressing Measurements
I. Using Measurements (p )
Section 2-3 Using Measurements
Chapter 3 Scientific Measurement 3.1 Using and Expressing Measurements
CH. 2 - MEASUREMENT I. Using Measurements.
MEASUREMENT Using Measurements C. Johannesson.
Accuracy vs. Precision & Significant Figures
Lesson 2 – Sci. Notation, Accuracy, and Significant Figures
CH. 2 - MEASUREMENT I. Using Measurements.
I. Using Measurements (p )
Chemistry Measurement Notes
2.b Using Scientific Measurements
I. Using Measurements (pp )
Uncertainty in Measurement
SCIENTIFIC NOTATION 5.67 x 105 Coefficient Base Exponent
2.3 Using Scientific Measurements
Aim: Why are Significant Figures Important?
Presentation transcript:

Accuracy vs. Precision Measurements need to accurate & precise. Accurate -(correct) the measurement is close to the true value. Precise –(reproducible) several measurements are close in value.

Good Precision Good Accuracy Poor Precision Poor Accuracy Good Precision Poor Accuracy Accuracy vs. Precision

Sources of Error human (mistakes in experiment, measurements, etc.) equipment (faulty or broken equipment, etc.) Calculating Error Accepted Value - true (correct) value - look it up. Experimental Value - measured in lab Error = Accepted value - Experimental value

Example You look up the density of water & it is 1 g/ml You calculate the density in the lab to be 0.8g/ml Error = 1 g/ml - 0.8g/ml = 0.2 g/ml

Percent Error Formula =  Accepted value- calculated value  x 100 Accepted value Example Accepted value for the density of water is 1 g/ml You calculate the density in the lab to be 0.8g/ml % error =  0.2 g/ml  x 100 = 20% error 1 g/ml absolute value of the error makes it a positive number The units cancel out so it is a %

Scientific Notation the product of two numbers: a coefficient & a power of 10. Ex: 3.6 x the coefficient must be greater than 1 but less than 10. there is only one number to the left of decimal. Ex:

Practice: Write the following in scientific notation: =_____________ =______________ 1343= _____________ 0.791= ____________

Scientific Notation on a Calculator GET OUT YOUR CALCULATOR!!! Type in the coefficient (use +/- if needed) EE or EXP (use 2nd or inv. if needed) exponent (use +/- if needed) Example: 3.0 x 10 4 Type in 3.0 push the EE or EXP Type in 4

Multiplying Scientific Notation (practice on your calculator) (3.6 x 10 4 ) x (2.22 x ) What’s happening? Multiply coefficients and ADD exponents. How to do it on a calculator: Type in 3.6 push the EE or EXP button Type in 4 (use +/- if needed) push multiply Type in 2.22 push the EE or EXP button Type in 2 (use +/- if needed) push =

Dividing Scientific Notation How to do it on a calculator: Follow the same steps as above but divide instead of multiply (1.98 x 10 4 ) = (2.34 x ) What’s happening mathmatically? Divide coefficients & SUBTRACT exponents.

Adding/Subtracting: 5.40 x x 10 2 = How to do it on a calculator: Follow the same steps as above but add/subtract instead of multiply. What’s happening? the exponents are made then same then add/subtract coefficients.

Significant Figures Rules: 1)In science we only record significant figures. 2) All digits are significant starting with the first non-zero digit on the left Examples:  3 sig fig  2 sig fig  6 sig fig

Significant Figures Rules: 3) Exception to the rules: If a whole number ends in zero the zeros at the right are not significant. Examples: 15,000  2 sig fig 150  2 sig fig 20,650  4 sig fig 6.0  2 sig fig

Significant Figures ?’s 1) How do you represent 15,000 if all the figures are significant? x ) What if only the 1st 3 places were significant? 1.50 x 10 4 Calculating Significant Figures Multiplying or dividing: the final answer can have no more sig figs than the least reliable measurement. 25 x 25 = 625  should only have 2 sig figs so round off to 630

Calculating Significant Figures Addition and Subtraction: Only keep sig figs when the places match up. 16.5? 8.44?  round off  round off