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HONORS CHEMISTRY

HONORS CHEMISTRY. August 3-4, 2011. Brain Teaser Quizlet. Open Note Quizlet Place Notes (Ch 2.6-2.8) on your desk. Brain Teaser. What do you think will happen if I light the bubbles on fire? Why? Demo Record Observations Was your prediction correct? Explain the science behind it.

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HONORS CHEMISTRY

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  1. HONORS CHEMISTRY August 3-4, 2011

  2. Brain Teaser Quizlet • Open Note Quizlet • Place Notes (Ch 2.6-2.8) on your desk

  3. Brain Teaser • What do you think will happen if I light the bubbles on fire? • Why? • Demo • Record Observations • Was your prediction correct? • Explain the science behind it

  4. Agenda • Brain Teaser Quizlet • Measurement Terms • Numbers Notes: • SI Units • Intro to Significant Figures • Measurement and Significant Figures Mini Lab • Scientific Notation • Homework • Significant Figures Worksheet • Qualitative and Qunatitative Worksheet • Blubbenbacher’s Foods Lab Report  Due This Friday

  5. Quantitative Measurements Examples Give results in a definite form, usually values 24L, 10 cm, 14 ºC Data Terms

  6. Qualitative Measurements Examples Give results in a descriptive, non-numeric form. The beaker was warm. The density was greater than that of water. Data Terms

  7. Accuracy Examples How close a measurement comes to the actual value of whatever is being measured Water freezes at 0º C, and boils at 100º C. How close is the measurement to the values. Data Terms

  8. Precision Examples Reproducibility of the measurement 9 out of 10 lab groups report the temperature of boiling water to be 95º C. A basketball player shoots 20 free throws, 18 of which bounce off the right side of the rim. Data Terms

  9. Accuracy vs. Precision • Target Practice • Accurate Precise Accurate & Precise

  10. Percent error Theoretical – Experimental x 100 = % error Theoretical

  11. Closure • Give and example of a qualitative and quantitative measurement.

  12. SI Units (Le SystémeInternationale) Scientists need to report data that can be reproduced by other scientists. They need standard units of measurement. Units of measurement Base Units • A base unit is a defined unit in a system of measurement • There are seven base units in SI. • Refer to the handout on SI Units

  13. Base Units

  14. Significant Figures Digits in a measurement that have meaning relative to the equipment being used Significant Figures

  15. Place What is the increment on the equipment? What you know for sure. Significant Figures

  16. Digits with meaning Examples Digits that can be known precisely plus a last digit that must be estimated. Refer to Examples on the board: 1. 2. 3. 4 Significant Figures

  17. Scale Reading and Uncertainty Uncertainty: Limit of precision of the reading (based on ability to guess the final digit). Existed in measured quantities versus counted quantities Refer to Example (2 rulers)

  18. Equipment to Evaluate To what place (tenths, hundredths, etc.) can these measurement instruments accurately measure? What place is the estimation? Triple beam balance Analytical balance Thermometer Graduated cylinders Beakers Ruler Burette Significant Figures: Mini Lab

  19. What do you notice? Depends on type of equipment being used. Depends on size of equipment used. Significant Figures

  20. Raw Data Rules How do you know how many sig figs? All digits 1-9 are significant. Zeros between significant digits are always significant. Trailing 0’s are significant only if the number contains a decimal point Zeros in the beginning of a number with a decimal point are not significant. Zeros following a significant number with a decimal are significant. Significant Figures

  21. Pacific to Atlantic Rule Examples Pacific = Decimal Present Start from the Pacific (left hand side), every digit beginning with the first 1-9 integer is significant 20.0 = 3 sig digits 0.00320400 = 6 sig digits 1000. = 4 sig digits Significant Figures

  22. Atlantic Rule to Pacific Examples Atlantic = Decimal Absent Start from the Atlantic (right hand side), every digit beginning with the first 1-9 integer is significant 100020 = 5 sig digits 1000 = 1 sig digits Significant Figures

  23. Practice • How many significant figures are in • 400.0 • 4000 • 4004 • 0.004

  24. Rally Rows How many significant figures are in • 0.02 • 0.020 • 501 • 501.0 • 5000 • 5000. • 5050 • 01.0050 • 50300 • 5.0300

  25. Things to consider What do significant figures tell you about the measurement equipment? If you wanted to measure the mass of a whale, what scale would you want to use? Would it matter if you know its mass accurately to 1 gram? If you wanted to measure the mass a grain of sand , what scale would you want to use? Would it matter if you know its mass accurately to 1 gram? Summary

  26. Instrument Measure • Need to make sure you are measuring and recording to the correct number of digits • Measure what you know for sure and then guess one more digit • Rulers • Draw a line on your paper and measure it to the correct number of digits • Beaker vs. graduated cylinder • Electronic balance vs. triple beam balance

  27. Scientific Notation

  28. Scientific Notation Example Shorthand way of expressing numbers that make them easier to work with 6.02 x 1023 2.34 x 105 3.78 x 10-3 Scientific Notation

  29. Any Patterns? Scientific Notation

  30. Rules Base number 1-9 Exponent = the number of times the decimal must be moved to bring the base number to 1-9. Numbers greater than 1 have a positive exponent, numbers less than 1 a negative exponent Scientific Notation

  31. Examples 0.0025 1,750,000 2.5 x 10-3 1.75 x 106 Scientific Notation

  32. Problems Express in Scientific Notation 0.0000678 998953000000 0.5768 Scientific Notation

  33. Problems Express in Standard Notation 1.567 x 10-3 6.02 x 1023 3.14 x 102 Scientific Notation

  34. Sig Figs in Scientific Notation • The numbers expressed in the scientific notation are significant • Examples: 5.02 x 104 5.02x 104 3 S.F • The number of significant figures in a set of numbers will be the # of sig figs in the scientific notation. • Examples: 50.200  5 SF  5.0200 x 101

  35. Survivor Science • Convert the following to exponential notation or to ordinary notation • Tell me how many Sig Figs. • 76 • 896745 • 8.9 x 103 • 3.45 x 10-1 • 0.222

  36. 6. 5.38 x 10-3 • 5 million • 8.00 x 104 • 0.00859 • 953.6

  37. What are Significant Digits? Examples Triple Beam Balance Graduated Cylinder All the certain digits plus the estimated digit in a measurement. How many decimal places can we count Significant Figures in Calculations

  38. Exact Numbers Examples Infinite # of sig figs Do not affect the number of significant digits in the final answer. They are not measurements!! 1000m = 1 km 12 in = 1 foot Significant Figures in Calculations

  39. Multiplication and Division Example The number with the smallest number of significant digits determines how many significant digits are allowed in the final answer. Volume of a box L x W x H (3.05m)(2.10m)(0.75m) 2 sig figs 4.8m3 Significant Figures in Calculations

  40. Example Density of a penny M = 2.53g V = 0.3mL D = M / V # significant figures allowed D = 8g/mL Significant Figures in Calculations

  41. Addition and Subtraction Example The number of significant digits depends on the number with the largest uncertainty. (you may be using different scales) Shoes 951.0 g Clothes 1407 g Ring 23.911 g Glasses 158.18 g Total 2540. g Significant Figures in Calculations

  42. Example What is the mass of a penny if, the weighing paper alone has a mass 0.67 g and weighing paper plus the penny has a mass of 3.2 g. 3.2 g -0.67 g 2.5 g Significant Figures in Calculations

  43. Remember A calculated number can only be as precise as the least precise measurement in the calculation. Significant Figures in Calculations

  44. Practice Calculate each of the following to the correct number of significant figures. Include units on your answer. • (25 g/mol)(4.0 mol) = • (3.48 in)(1.28 in)(0.010 in) = • 2.06 cm + 1.8 cm + 0.004 cm = • If the mass of a lead cube is 176.91 g and it measures 2.51cm x 2.49 cm x 2.49 cm, what is the density of lead?

  45. Practice Calculate each of the following to the correct number of significant figures. Include units on your answer. • (25 g/mol)(4.0 mol) =1.0 x 102 • (3.48 in)(1.28 in)(0.010 in) = .045 in3 • 2.06 cm + 1.8 cm + 0.004 cm = 3.9 cm • If the mass of a lead cube is 176.91 g and it measures 2.51cm x 2.49 cm x 2.49 cm, what is the density of lead? 11.3 g/cm3

  46. Rally rowsSig figs in Calculations • 12 cm + 0.031cm + 7.969 cm = • (41.025 g - 23.38g) ÷ 8.01 mL= • 17.3 cm x 6.2 cm + 3.28 cm2 = • 109.3758 m2  45.813 m = • What is the mass of Salt (NaCl) if the sodium has a mass of 22.99 g and the Cl a mass of 35.5g?

  47. Partner Challenge

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