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Chapter 2--Measuring/Calculating

Chapter 2--Measuring/Calculating. SI units. Basic units of System International: Length meter m Mass kilogram kg Volume liter l Time second s Pressure pascal p Temperature kelvin K Quantity mole mol . Prefixes. Metric prefixes to know:

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Chapter 2--Measuring/Calculating

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  1. Chapter 2--Measuring/Calculating

  2. SI units • Basic units of System International: • Length meter m • Mass kilogram kg • Volume liter l • Time second s • Pressure pascal p • Temperature kelvin K • Quantity mole mol

  3. Prefixes • Metric prefixes to know: • Kilo k1000 (103) • Mega M million (106) • Deci d .1 (10-1) • Centi c .01 (10-2) • Milli m .001 (10-3) • Microµ .000001(millionth)(10-6) • Nano n .000 000 001(billionth • Pico p .000 000 000 001(trill)

  4. Factor/Label Method or dimensional analysis Conversion factors to know: Length: 1Km = 1000 M 1M = 1000mm 1M = 100 cm 1M = 10 dm

  5. Mass: 1 Kg = 1000g 1 g = 1000mg 1g = 100 cg

  6. Volume: 1L = 1000 ml 1L = 1000cc 1ml = 1 cm3 (cc) 1dm3 = 1L

  7. Conversion: Convert: a) 60 g to mg b) 134 mg to kg c) 150 cm to km Which is shortest? 12 cm, 100mm, or .5 meters

  8. Vocab • Weight---measurement of the gravitational pull • newton—unit of wt • scale—measures wt • Mass---measurement of the quantity of matter • Kg, g, mg • Balance– measures mass

  9. Metric Measurement • Diameter of quarter cm • Distance from NY to LA Km • New pencil cm • Thickness of dime mm

  10. Metric Measurement Mass measurement Nickel g Newborn baby kg Chocolate chip mg 10 speed bike kg

  11. Metric Measurement body temp 37oC room temp 250C inside refrigerator 5oC water boils 1000C water freezes 00 C

  12. Temperature • Kelvin = 0C + 273 • Water boils at 3730 K • Water freezes at 2730 K

  13. Vocab • Accuracy---refers to how close a measurement is to the accepted value • Precision---refers to how close a set of measurements are to each other • ex: 22.1 cm, 22.09 cm, 21.99 cm

  14. Percent Error • All measurements are uncertain and we measure the margin of error present by: • % error = your value – lit. value_____ x100 literature value

  15. Percentage Error • Example: If the temperature of the student was determined to be 100.40F, what is the percentage error? • % error = 100.4 -98.6 x 100 • 98.6 • = 1.82% • (Difference between your value and literature value is always positive)

  16. Vocab • Derived units---units used to express measurements of speed, area, volume, density) • Must include more than one basic unit • miles/hour • cm x cm = cm2 • cm x cm x cm = cm3 • mass/volume g/ ml

  17. Significant Digits • Rules for assigning significant digits: • 1) all non-zero digits are significant • 22.4 liters 3 sig fig • 2) trapped zeros are significant • 22.004 liters 5 sig fig • 3) ending zeros at the right of the decimal are significant • 22.00 liters 4 sig fig

  18. Significant Digits • 4) leading zeros are NOT significant • 0.000345 liters 3 sig fig • 5) Ending zeros on an exact number(one that no estimation is needed) are significant 200 cars = 3 sig fig • 6)Ending zeros on non-exact numbers are not significant 200 kg = 1 sig fig

  19. Sig Fig • Examples: • 10.0 350 people • 0.020 1600 grams • 34.05 • 45.600 • 0.00405 • 102.00

  20. Sig Fig • Rules governing the number of significant figures in a calculated answer: • 1) When you add or subtract, the number you get as an answer can have no more digits to the right of the decimal than there are in the number which has the least number of digits to the right of the decimal

  21. Sig Fig • 100.2 • 46.32 • 7.538 • ______________ • 154.058 round off to 154.1

  22. Sig Fig • B) 438.686 • 78.22 • 360.466 round to 360.47

  23. Sig Fig • 2) When you multiply or divide, your answer can have no more significant figures than the multiplier, divisor, or dividend that has the least number of significant figures )

  24. Sig Fig • A) 46.25 X 0.25 = 11.5625 rd off to 12 • B) 0.70 = 0.015053 can have only 2 sf • 465 • 1.5 X 10-2

  25. Sig Fig • 350 X 6.0 = 2100 or 2.1 X 103 .0045 x .105 = .0004725 = 4.7 X 10-4

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