1 / 24

Measurements and Conversions

Measurements and Conversions. Why Measure?. Measurements give specific information Different types: - Base Units: System International Units (or Metric) Standard for many scientific measurements - Derived Units Combinations of base units Ex: density or volume. Metric Units

onella
Télécharger la présentation

Measurements and Conversions

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. Measurements and Conversions

  2. Why Measure? • Measurements give specific information • Different types: - Base Units: System International Units (or Metric) • Standard for many scientific measurements - Derived Units • Combinations of base units • Ex: density or volume

  3. Metric Units Mass – the amount of matter in an object, grams (g) Volume – the amount of space an object occupies, liter (L) Length – distance between two points, meter (m)

  4. Metric Prefixes

  5. Converting with metric units • K H D __ d c m • Place 1 under starting prefix • Place 2 under ending prefix • Draw an arrow from 1 to 2. This is the direction to move the decimal point. • Count the number of places to go from 1 to 2. Be sure to count the __ space. • Move decimal point and rewrite number.

  6. Make the following metric conversions 13.5 g  ___ kg 2.75 mL  ___ L 150 mm  ___cm0.0150 m  ___cm 0.195 cg  ___ mg 0.750 L  ___mL 2.46 mg ___ kg 5.79 HL  ___ L 7.53 km  ___cm0.0432 g  ___mg 4150 cL ___ L 739 dm  ___ m 81.8 cg  ___kg418.2 m  ___ km

  7. Scientific Notation – a way of showing very large or small numbers. • 4.7 x 103 4.7 E 3 4.7 exp3 • 4.7 x 10 x 10 x 10 = 4,700 • Only significant numbers remain • The “number out front” is only allowed to have one nonzero digit to the left of the decimal point.

  8. Converting TO Scientific Notation • Place the decimal after the first digit • Count from the original decimal place to the new location. • That number will become the exponent. • If you counted: • To the left (starting # > 1) then + exponent • To the right (starting #< 1) then - exponent • Write “new” number x 10exponent • Do not write any placeholding zeros • Non-significant numbers

  9. Converting FROM Scientific Notation • The exponent or power tells how many places the decimal point will be moved. • If the exponent is positive, the decimal point moves to the right. - The number will be > 1 • If the exponent is negative, the decimal point moves to the left. - The number will be < 1

  10. Warm-Up • Convert the following: 1. 41,300 L to kL 2. 13,200 kg to g 3. 72 cm to mm • 41.3 kL • 13,200,000g • 720mm

  11. Warm-Up • Express is Scientific Notation: • 1600 • 0.0053 • 134.8 1. 1.6 x 103 2. 5.3 x 10-3 3. 1.348 x 102

  12. Reliability of Measurements • Exact numbers - counting numbers - Not measurements - A stated value that is certain • Example: 100 years = 1 century, 1 foot = 12 inches • Measured numbers- have uncertainty because of the equipment/device used and the observer

  13. Accuracy and Precision • Accuracy - How close the measured value is to the accepted value • Precision - How close a series of measurements are to each other

  14. Significant Figures • Scientists use significant figures to show how precisely an experiment was performed • Significant Figures (sig figs) – all known digits in a measurement plus one estimated digit. • Scientists use rules to determine the number of significant figures in a particular value

  15. When to use Sig Fig • When something is MEASURED • Not when something is COUNTED

  16. Coast to Coast Sig Figs Atlantic/Pacific Rule: • If a decimal point is absent, count from the Atlantic (right) side starting with the first nonzero digit. • If a decimal point is present, count from the Pacific (left) side starting with the first nonzero digit

  17. Coast to Coast practice • 47.08020 • 10 • 5400600 • 1.158 • 0.007013 • 100.

  18. Rounding numbers in calculations • Add/subtract: the answer will have the same number of places past the decimal point as the measurement with the fewest places past the decimal point. • Multiply/divide: the answer will have the same number of sig figs as the measurement with the fewest number of sig figs. • Rounding off numbers: 0-4 drop, 5-9 add 1 • Defined or exact numbers have an infinite number of significant figures.

  19. WHEN to round off significant figures • When the rules for rounding change • i.e. going from addition  division or multiplication  addition • At the end of the problem, and you are giving the final answer

  20. Conversions that you are responsible for knowing… • 12 in = 1 ft • 3 ft = 1 yd • 5280 ft = 1 mile • 60 sec = 1 min • 60 min = 1 hr • 24 hr = 1 day • 7 day = 1 wk • 365.25 days = 1 yr • 16 oz = 1 lb • 2000 lb = 1 ton • 8 oz = 1 cup • 2 cups = 1 pint • 2 pints = 1 quart • 4 quarts = 1 gallon

  21. Unit Analysis/Dimensional Analysis • A method of converting from 1 set of units to another set of units using a series of conversion factors. • A conversion factor is a fraction made from the two parts of the equivalency. • 12 in. = 1 ft • Each equivalency can produce two conversion factors.

  22. Convert 22 inches to feet • List possible conversion factors: • Set up grid with starting number and units in the upper left side • Plug in conversions so that the same units are on the diagonal

  23. Unit Analysis Practice • 5.75 min  months • 135 km  cm • 17.5 oz  gal • 1.5 mile  inch • 145 mg  hg • 135 mL  L

  24. 5.75 min  month • 5.75 min_ 1 hr 1 day 1 yr 12 mos= 1.31 x 104 months • 60 min 24 hr 365.25 day 1 yr • 135 km  cm • 135 km 1000 m 1 cm = 13,500,000 cm • 1 km 0.01 m • 17.5 oz  gal • 17.5 oz 1 qt 1 gal = 0.138 gal • 32 oz4 qt • 1.5 mile  inch • 1.5 mile 5280 ft 12 in = 95,000 in • 1 mile 1 ft

More Related