1 / 25

Chemistry Mathematics

Chemistry Mathematics. Measurement 3221.MATH.1; 3221.MATH.2. Learning Goals. Write the names and abbreviations for the units used in measurements of length, volume, and mass Label measurements as accurate or precise Write a number in scientific notation

raven
Télécharger la présentation

Chemistry Mathematics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemistry Mathematics Measurement 3221.MATH.1; 3221.MATH.2

  2. Learning Goals • Write the names and abbreviations for the units used in measurements of length, volume, and mass • Label measurements as accurate or precise • Write a number in scientific notation • Determine the number of significant figures in measured numbers • Adjust calculated answers to the correct number of significant figures. • Use numerical prefixes to do metric conversions through decimal placement.

  3. Units of Measurement • 2 parts to any measurement: number and unit • Units are extremely important in reporting and working with scientific numbers and they must be included • The number of digits in a measurement reflects a degree of precision: the more digits in the measurement, the more precise it is; fewer digits, less precision Why is this important??

  4. Read the following: • When my son was 7 he walked 3, and when he was 4 he threw his baseball 8 and said his school was 5 away. • When my son was 7 months old he walked 3 steps, and when he was 4 years old he threw his ball 8 feet and said his school was 5 minutes away. • The units make all the difference!!!

  5. Uncertainty in Measurement • Accuracy: how close a measurement is to the accepted value • Precision: degree of “agreement” between several measurements of the same quantity • A MEASUREMENT CAN ONLY BE AS PRECISE AS THE INSTRUMENT USED!!!

  6. Accuracy and Precision Illustration

  7. Two major systems: • English system -used only in the United States -inches, yards, pounds 2. Metric system -International System (SI system) is the system of measurement for the scientific world -centimeters, meters, kilograms

  8. Fundamental SI Units

  9. What do the units mean? • Unit: predefined standard of measurement or basis of comparison • Second: 60 s = 1 min • 1 meter is slightly longer than 1 yard a 100 yd football field is only 91.4 m • 1 kg = 2.205 lb Remember: mass is different than weight, which is affected by gravity

  10. Prefixes in SI system

  11. Prefix Multipliers • Used with the standard units of the SI system, rather than having different “units” with which to make comparisons • Multipliers change the value of the unit by powers of 10 • Prefix multipliers allow us to express a wide range of measurements in units that are similar in size to the quantity we are measuring • Choose the prefix that is most convenient for a particular measurement

  12. Derived SI Units ANY UNIT OF LENGTH, WHEN CUBED (RAISED TO THE THIRD POWER), BECOMES A UNIT OF VOLUME 1 cm3 = 1 mL 1 dm3 = 1 L

  13. Uncertainty in Measurements • Measured numbers: numbers you obtain when you use a measuring tool to determine your height, weight, or temperature • To report a measurement, first read the numerical value of the marked line. Finally, estimate between the smallest marked lines. • When an estimate ends on a marked line, a zero is written for the estimated digit.

  14. Significant Figures Scientific numbers are recorded so that every digit is certain except for last, which is estimated. 48.872 When recording measurements, only estimate ONE digit beyond the smallest division on the instrument being used!!

  15. Reading Volume • Meniscus: the curved portion at the top of a volume of liquid • Most liquids have a concave meniscus, however mercury has a convex meniscus

  16. Rules for determining significant figures: • All nonzero digits are significant 1.05 0.0110 2. Interior zeros (zeros between 2 numbers) are significant 1.0208 50.1 3. Trailing zeros (zeros after a decimal point) are significant 5.10 3.00 4. Leading zeros ( zeros to the left of the first nonzero number) are not significant. They only serve to locate the decimal point. 0.00005

  17. Practice Problems • 0.00789 • 2.0012 • 0.001 • 4.100 • 0.1000 • 2.65001 • 100.25

  18. Solutions to Problems • 0.00789 3 significant figures (0.00789) • 2.0012 5 (2.0012) • 0.001 1 (0.001) • 4.100 4 (4.100) • 0.1000 4 (0.1000) • 2.65001 6 (2.65001) • 100.25 5 (100.25)

  19. Exact numbers Exact numbers have an unlimited number of significant figures • 3 sources 1. accurate counting of discrete objects 3 atoms means 3.000000 atoms 2. defined quantities 100 cm = 1 m means 100.000 cm =1.00m 3. integral numbers that are part of an equation radius = diameter/ 2

  20. Significant Figures in Calculations • In multiplication or division, the result carries the same number of significant figures as the factor with the fewest significant figures • In addition or subtraction, the result carries the same number of decimal places as the quantity carrying the fewest decimal places

  21. Scientific Notation • Used to write cumbersome numbers in a compact manner 1.2 x 10-10 exponent (n) Decimal partexponential part To convert a number to scientific notation: 1. move the decimal point to obtain a number between 1 and 10. 2. multiply by 10 raised to the number of places you moved the decimal point -if decimal moved left: positive exponent -if decimal moved right: negative exponent

  22. Practice

  23. Percent Error • The percentage by which a measurement deviates from the accepted value • NO MEASURED VALUE WILL EVER BE EXACT!! • % Error = Accepted Answer - Experimental Answer x 100 Accepted Answer

  24. Practice Problems 1. Samantha S. Sloppiness measured the volume of her soda before she drank it for her midmorning snack. She measured the volume of the 12 oz. bottle to be 14 oz. 2. Clyde Clumsy was directed to weigh a 500 g mass on the balance. After diligently goofing off for ten minutes, he quickly weighed the object and reported 458 g. 3. Pretty Patty Pestilence had casually recorded her grades for the nine weeks in her notebook. She concluded she had 250 points out of 300 for the grading period. However, Miraculous (chemistry teacher) determined she had 225 points out of 300 and awarded her a "C" for the grading period. 4. Drew D. Ditzy came to Miraculous with a problem. Drew was told to measure 50 cm of copper wire to use in an experiment. Since his ruler only measured to 45 cm he used this amount of wire and his experiment was a failure. 5. Henry Heavyfoot was just arrested for speeding by Officer O'Rourke for traveling 65 mph in a 55 mph zone. Henry claimed his speedometer said 55 mph not 65 mph.

More Related