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THE METRIC SYSTEM

Learn about the metric system, its units of measurement, and conversions. Explore significant figures and the concepts of accuracy and precision in measurements. Includes a tutorial on significant figures.

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THE METRIC SYSTEM

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  1. THE METRIC SYSTEM SOME DAY, WE’LL BE TRADING OUR FEET FOR METERS.

  2. MEASUREMENT NUMBERS ARE OBTAINED BY COUNTING OR DEFINITION MEASUREMENTS ARE OBTAINED BY COMPARING THE OBJECT IN QUESTION TO A STANDARD UNIT NUMBERS ARE EXACT, BUT MEASUREMENTS ARE INEXACT (HAVE A CERTAIN DEGREE OF ERROR). MEASUREMENTS CONSIST OF TWO PARTS – A NUMERIC VALUE AND A UNIT.

  3. THE SO CALLED “ENGLISH” SYSTEM OF MEASUREMENTS IS STILL USED IN A FEW COUNTRIES, INCLUDING THE U.S. IT IS A SYSTEM THAT GOES BACK TO ROMAN TIMES, AND IT HAS BEEN CHANGED SEVERAL TIMES. FOR EXAMPLE, THE ROMAN FOOT WAS SLIGHTLY LESS THAN 12 INCHES, AND THE ANGLO-SAXON FOOT WAS SLIGHTLY MORE.

  4. THE FOOT AS WE KNOW IT WAS STANDARDIZED UNDER THE REIGN OF HENRY THE 1 (1100 – 1135). THE ROMAN MILE HAD BEEN 5000 FEET, BUT THIS WAS CHANGED TO 5280 FEET TO MAKE IT AN EVEN NUMBER OF FURLONGS. THE SYSTEMS OF MEASURING VOLUME AND WEIGHT ARE EQUALLY CRAZY.

  5. WITH INTERNATIONAL TRADE, MOST OF THE WORLD HAS GONE TO THE SI OR METRIC SYSTEM.

  6. (CNN) -- NASA lost a $125 million Mars orbiter on September 23, 1999 because a Lockheed Martin engineering team used English units of measurement while the NASA’s team used the more conventional metric system for a key spacecraft operation.

  7. THE METRIC SYSTEM IS BASED ON THREE DEFINED UNITS. m the meter for length kg the kilogram for mass s the second for time ALL THE OTHER UNITS ARE DERIVED FROM THESE THREE. BY COMPARISON: 1 m = 1.094 yard 1 kg = 2.205 lb 1 s = 1 s

  8. WE CAN COMBIND THE KILOGRAM, THE METER, AND THE SECOND TO MAKE MORE UNITS. AREA = LENGTH X LENGTH = m x m = m2 VOLUME = L X L X L = m x m x m = m3 1 m3 = 1,000 liters The liter is the unit we will use for volume. 1 liter = 1.05669 quarts = 1.06 quarts

  9. THE ORIGINAL METRIC SYSTEM WAS STARTED IN FRANCE IN 1670. THE SYSTEM, AS WE KNOW IT, WAS PUT IN PLACE IN 1960, AND IS KNOWN AS THE INTERNATIONAL SYSTEM OF MEASUREMENT, OR "Système International” IN FRENCH OR SI.

  10. THE MORE COMMON PREFIXES

  11. OUR MORE COMMON UNITS OF MEASURE: MASS: gram, g 454 grams = 1 lb 1 kilogram, kg = 1000 g 1 milligram = 0.001 g VOLUME: liter, l 1 l = 1.06 quarts 1 milliliter, ml = 0.001 l LENGTH: meter, m 1 meter = 1.09 yard 1 cm = 0.01 m 2.54 cm = 1 inch 1 mm = 0.001 m

  12. SOME COMPARISONS LENGTH: A DIME IS 1 mm THICK A QUARTER IS 2.5 cm DIAMETER AV. HEIGTH OF ADULT MALE 1.8 m MASS: A NICKEL IS 5 g A 120 lb PERSON HAS A MASS OF 55 kg VOLUME: A 12 oz SODA HAS A VOLUME OF 360 ml

  13. ANOTHER IMPORTANT MEASUREMENT IS TEMPERATURE. TEMPERATURE IS A MEASURE OF THE AVERAGE KINETIC ENERGY. THE HIGHER THE TEMPERATURE, THE FASTER THE PARTICLES THAT MAKE UP THE OBJECT ARE VIBRATING (SOLID) OR MOVING (LIQUID OR GAS). THERE ARE THREE TEMPERATURE SCALES THAT ARE USED – FAHRENHEIT, CELCIUS, AND KELVIN.

  14. THESE SCALES DIFFER BY THE TEMPERATURES SELECTED FOR THE REFERENCE POINTS. THEY ALL USE THE SAME THREE REFERENCE POINTS: - THE BOILING POINT OF WATER - THE FREEZING POINT OF WATER - ABSOLUTE ZERO THE EXTERNAL PRESSURE IS 1 ATMOSPHERE (760 MM Hg) FOR THE BOILING POING AND THE FREEZING POINT.

  15. THE CONVERSION EQUATIONS REFLECT THE DIFFERENCES IN NUMBER OF DEGREES BETWEEN THE REFERENCE POINTS AND THE VALUES SELECTED FOR THE REFERENCE POINTS.

  16. SOME OF THE EQUIPMENT WE WILL USE

  17. ANY MEASUREMENT HAS TWO PARTS – A NUMBER AND A UNIT. 12 grams number units WE REPORT A MEASUREMENT BY RECORDING ALL THE CERTAIN DIGITS PLUS THE FIRST UNCERTAIN DIGIT. THESE ARE CALLED SIGNIFICANT FIGURES.

  18. WHEN YOU ARE DOING AN EXPERIMENT, YOU SHOULD RECORD YOUR RESULTS TO THE APROPRIATE NUMBER OF SIGNIFICANT FIGURES – THIS WAY, THE UNCERTAINTY IN MEASUREMENT WILL BE KNOWN. FOR EXAMPLE, RATHER THAN WRITING 25 ml IF YOUR MEASUREMENT IS ACCURATE TO THE NEAREST 0.01 ml, YOU WOULD WRITE 25.00 ml

  19. A COUPLE OF TERMS YOU WILL HERE IN REFERENCE TO MEASUREMENTS ARE: ACCURACY – REFERS TO THE AGREEMENT OF A PARTICULAR VALUE WITH THE TRUE VALUE. PRECISION – REFERS TO THE DEGREE OF AGREEMENT AMONG SEVERAL VALUES.

  20. http://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.htmlhttp://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.html THIS IS A TUTORIAL ON THE USE OF SIGNIFICANT FIGURES. WORK THE FIRST 10 SAMPLE PROBLEMS.

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