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Basic Measurement Skills 2

Basic Measurement Skills 2. Unit 1 Chemistry. What are the objectives?. Significant figures and calculations Dimensional analysis English to English Metric to Metric English to Metric Metric to English Time Conversions Complex unit Temperature conversions. Connecting to your world.

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Basic Measurement Skills 2

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  1. Basic Measurement Skills 2 Unit 1 Chemistry Mrs. Medina

  2. What are the objectives? • Significant figures and calculations • Dimensional analysis • English to English • Metric to Metric • English to Metric • Metric to English • Time Conversions • Complex unit • Temperature conversions Mrs. Medina

  3. Connecting to your world In 1999, CNN NASA lost a 125 million Mars orbiter (crash landed) because a Lockheed Martin engineering team used English units of measurement while NASA’s team used the more conventional metric system for a key spacecraft operation, according to a review finding released Thursday. Mrs. Medina

  4. Significant Figures 1.65 cm A significant figure is a measurement that includes all the figures KNOWN and the last figure which is ESTIMATED. 1.65 cm is how many significant figures? Mrs. Medina

  5. Rules of Significant Figures • Rule #1: All nonzero digits are significant • Rule #2: Zeros in between nonzero numbers are significant • Rule #3: Zeros to the left of nonzero numbers are NOT significant. They are placeholders. • Rule #4: Zeros to the right of nonzero numbers are significant ONLY IF a decimal point is present or if it’s scientific notation. • Rule #5: If it’s not a measurement then it is said to have unlimited significance. • Conversion factors and things we can count Mrs. Medina

  6. Rule #1: All nonzero digits are significant 6 SF 3 SF 1 SF 9 SF 9345.34 cm 143 g 7 in 346598439 m Mrs. Medina

  7. Rule #2: Zeros in between nonzero numbers are significant 90.075 5 SF 3 SF 503 4 SF 5003 4 SF 500.3 Mrs. Medina

  8. Rule #3: Zeros to the left of nonzero numbers are NOT significant. They are placeholders. 0.75 2 SF 2 SF 0.075 2 SF 0.0075 3 SF 0.0304 Mrs. Medina

  9. Rule #4: Zeros to the right of nonzero numbers are significant ONLY IF a decimal point is present or if it’s scientific notation. 700 1 SF 3 SF 700. 1 SF 400 3 SF 4.00 x 102 Mrs. Medina

  10. Rule #5: If it’s not a measurement then it is said to have unlimited significance. Conversion factors and things we can count • 1 in = 2.54 cm • 1 m = 103 mm • 17 cars • 450 atoms • 2 students Unlimited significance They do not affect sig figs in calculations Mrs. Medina

  11. Significant figures Mrs. Medina

  12. Rounding 1809.3049 1809.305 1809.31 1809.3 1809 1810 1800 2000 Underline your number and look at the neighbor on the right and if its 5 and above, give your number a shove! 4 and below, leave your number alone! Use placeholders when rounding on the left of the decimal and/or scientific notation. Mrs. Medina

  13. Significant figures and Calculations • Adding and Subtracting • Least number of decimal places • Your answer will have the same number of decimal places as the measurement with the least number of decimal places (least precise). • Multiplying and Dividing • Least number of significant figures • Your answer will have the same number of significant figures as the measurement with the least number of significant figures. Mrs. Medina

  14. Significant figures and Calculations What is the least number of decimal places? 12.52 349.0 + 8.24 369.76 = 369.8 What is the least number of significant figures? 7.55 m x 0.34 m 2.567 m2 = 2.6 m2 • Adding and Subtracting • Least number of decimal places • Multiplying and Dividing • Least number of significant figures Mrs. Medina

  15. Significant figures and calculations Mrs. Medina

  16. Quantities and OFFICIAL SI units Mrs. Medina

  17. Commonly used units UnitsSymbolUsed to Measure: liter L volume meter m distance/length gram g mass (weight) Joule J energy second s time Pascal Pa pressure Mrs. Medina

  18. Dimensional Analysis • One of the best methods to solve a problem using the units (or dimensions) of the measurements. • Consistent problem solving approach • Reduces errors in algebra • Reinforces unit conversion • Simplifies computation • Improves understanding of math applications • Multiple ways to solve the same problem Mrs. Medina

  19. Conversion Factors Conversion Factors are usefulin solving problems in which a given measurement must be expressed in some other unit of measure A quantity can be expressed several different ways When a measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quantity measured remains the same. A conversion factor is a ratio of equivalent measurements; the ratio equals 1 or unity Conversion factorsare exact Numbers so they have unlimited significant numbers; they do not affect the rounding of a number. Mrs. Medina

  20. Dimensional Analysis Steps How many hours are in 2530 seconds? Read question and identify any given information. Starting point = 2530 seconds Final point = ? hours 2. Write your starting point and your final point. 2530 seconds  ? hours 3. Find conversion factors (relationships) between your destination. 60 seconds = 1 minute 60 minutes = 1 hour 4. Add in between steps to your starting point and final point. 2530 seconds  ? Minutes  ? hours Mrs. Medina

  21. Dimensional Analysis Steps How many seconds are in 25 hours? Place your starting point and setup the first conversion. Use the first relationship (60 seconds = 1 minute). Match up the units top and bottom. Use the next relationship (60 minutes = 1 hour). Match up the units top and bottom. Mrs. Medina

  22. Dimensional Analysis steps Once done, cancel all the units from left to right. Multiply the top…multiply the bottom…divide top by bottom Mrs. Medina

  23. Dimensional Analysis: English to English Starting point = 9320 in Final point = ? mi 12 inches = 1 foot 5280 feet = 1 mile 9320 in  ? Ft  ? miles How many miles is 9,320 inches? Mrs. Medina

  24. Metric System Mrs. Medina

  25. Combining Prefixes and Units Values in the metric system must contain a unit and the units are typically preceded by a prefix milli gram = + milligram (mg) Prefixes tera (T) giga (G) mega (M) kilo (k) hecto (h) dek(c)a (da) deci (d) centi (c) milli (m) micro (µ) nano (n) Units liter (L) meter (m) gram (g) Joule (J) second (s) Pascal (Pa) kilo + liter = kiloliter (kL) centi + meter = centimeter (cm) Mrs. Medina *The lists of prefixes & units are not all-inclusive

  26. Metric System Substitute the unit where you see the word “base” Mrs. Medina

  27. Dimensional Analysis: Metric to Metric Starting point = 2.54 Gm Final point = ? mm 1 Gm = 109 m 1 m = 103 mm 2.54 Gm ? m  ? mm How many mm are in 2.54 Gm? Mrs. Medina

  28. Dimensional Analysis:English and Metric Conversions Starting point = 32.2 km Final point = ? in 32.2 km  ? m  ? cm  ? in 1 km = 1000 m 1 m = 102 cm 2.54 cm = 1 in Round to 3 SF How many inches in 32.2 km? Mrs. Medina

  29. Dimensional Analysis: Time Problems 60 sec = 1 min 60 min = 1 hr 24 hr = 1 day 7 day = 1 wk 52 wk = 1 yr 365 day = 1 yr 10 yr = 1 decade 10 decade = 1 century 100 yr = 1 century 10 century = 1 millenium Convert 1.25 years into seconds. 1 yr = 365 day 1 day = 24 hr 1 hr = 60 min 1 min = 60 sec Starting point = 1.25 yr Final point = ? sec 1.25 yr  ? Day  ? hr  ? Min  ? sec Round to 3 SF You are responsible for knowing time relationships Mrs. Medina

  30. Dimensional Analysis: Complex Units 1 mi = 5280 ft 3 ft = 1 yd 1 hr = 60 min Starting point = 3.50 mi/hr Final point = ? yd/min 3.50 mi/hr  ? yd/min mi  ft  yd hr  min Round to 3 SF A student walks at a brisk 3.50 mi/hr. Calculate the student’s speed in yards/minute. Mrs. Medina

  31. Dimensional Analysis:Complex units m3 to cm3 or yd3 Mrs. Medina

  32. Temperature Conversions • Temperature is a measure of how hot or cold an object is compared to another object. • indicates that heat flows from the object with a higher temperature to the object with a lower temperature. • is measured using a thermometer. • 4 Scales: • Fahrenheit • Celsius • Kelvin • Rankine Mrs. Medina

  33. Extra conversion factors Mrs. Medina

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