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Measurement

Measurement. 100 mL Graduated Cylinder Units of Measuring Volume Reading a Meniscus Units for Measuring Mass Quantities of Mass SI-English Conversion Factors Accuracy vs. Precision Accuracy Precision Resolution SI units for Measuring Length Comparison of English and SI

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Measurement

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    1. Measurement 100 mL Graduated Cylinder Units of Measuring Volume Reading a Meniscus Units for Measuring Mass Quantities of Mass SI-English Conversion Factors Accuracy vs. Precision Accuracy Precision Resolution SI units for Measuring Length Comparison of English and SI Units Reporting Measurements Measuring a Pin Practice Measuring

    3. 100 mL Graduated Cylinder

    4. Instruments for Measuring Volume

    5. Units of Measuring Volume UNITS OF MEASURING VOLUME A measurement has two parts: a number and a unit. Note: NO NAKED NUMBERSUNITS OF MEASURING VOLUME A measurement has two parts: a number and a unit. Note: NO NAKED NUMBERS

    6. Reading a Meniscus

    7. Units for Measuring Mass UNITS FOR MEASURING MASS Mass amount of substance present. Does not change when going to the moon. Mass is measured on a pan balance. Weight related to gravity. Your weight is about 1/6 on the moon and 2.36X on Jupiter. As gravity increases your weight increases. Pull of gravity on jet fighter planes make your arms and legs very heavy and g-forces increase. Weight is measured on a scale.UNITS FOR MEASURING MASS Mass amount of substance present. Does not change when going to the moon. Mass is measured on a pan balance. Weight related to gravity. Your weight is about 1/6 on the moon and 2.36X on Jupiter. As gravity increases your weight increases. Pull of gravity on jet fighter planes make your arms and legs very heavy and g-forces increase. Weight is measured on a scale.

    9. Quantities of Mass

    11. Scientific Notation: Powers of Ten

    13. Metric Article

    14. SI-US Conversion Factors Dominoes ActivityDominoes Activity

    15. Accuracy vs. Precision Scientists repeat experiments many times to increase their accuracy. Scientists repeat experiments many times to increase their accuracy.

    16. Accuracy vs. Precision Scientists repeat experiments many times to increase their accuracy. Scientists repeat experiments many times to increase their accuracy.

    17. http://antoine.frostburg.edu/chem/senese/101/measurement/slides/sld016.htmhttp://antoine.frostburg.edu/chem/senese/101/measurement/slides/sld016.htm

    18. Types of errors

    19. Errors Systematic Errors in a single direction (high or low) Can be corrected by proper calibration or running controls and blanks. Random Errors in any direction. Cant be corrected. Can only be accounted for by using statistics. Systematic error is when you get the same mistake every time you perform a measurement, and random error is when the mistake varies randomly. Its much easier to compensate for systematic error than for random error.Systematic error is when you get the same mistake every time you perform a measurement, and random error is when the mistake varies randomly. Its much easier to compensate for systematic error than for random error.

    20. Accuracy Precision Resolution

    21. Accuracy Precision Resolution

    22. Standard Deviation One standard deviation away from the mean in either direction on the horizontal axis (the red area on the above graph) accounts for somewhere around 68 percent of the people in this group. Two standard deviations away from the mean (the red and green areas) account for roughly 95 percent of the people. And three standard deviations (the red, green and blue areas) account for about 99 percent of the people. The more practical way to compute it... In Microsoft Excel, type the following code into the cell where you want the Standard Deviation result, using the "unbiased," or "n-1" method: =STDEV(A1:Z99) (substitute the cell name of the first value in your dataset for A1, and the cell name of the last value for Z99.) One standard deviation away from the mean in either direction on the horizontal axis (the red area on the above graph) accounts for somewhere around 68 percent of the people in this group. Two standard deviations away from the mean (the red and green areas) account for roughly 95 percent of the people. And three standard deviations (the red, green and blue areas) account for about 99 percent of the people. The more practical way to compute it...In Microsoft Excel, type the following code into the cell where you want the Standard Deviation result, using the "unbiased," or "n-1" method: =STDEV(A1:Z99) (substitute the cell name of the first value in your dataset for A1, and the cell name of the last value for Z99.)

    23. SI Prefixes kilo- 1000 deci- 1/10 centi- 1/100 milli- 1/1000

    24. SI System for Measuring Length

    25. Comparison of English and SI Units

    26. Reporting Measurements Using significant figures Report what is known with certainty Add ONE digit of uncertainty (estimation) By adding additional numbers to a measurement you do not make it more precise. The instrument determines how precise it can make a measurement. Remember, you can only add ONE digit of uncertainty to a measurement.By adding additional numbers to a measurement you do not make it more precise. The instrument determines how precise it can make a measurement. Remember, you can only add ONE digit of uncertainty to a measurement.

    27. Measuring a Pin

    28. Practice Measuring PRACTICE MEASURING Estimate one digit of uncertainty. a) 4.5 cm b) * 4.55 cm c) 3.0 cm *4.550 cm is INCORRECT while 4.52 cm or 4.58 cm are CORRECT (although the estimate is poor) By adding additional numbers to a measurement you do not make it more precise. The instrument determines how precise it can make a measurement. Remember, you can only add ONE digit of uncertainty to a measurement. In applying the rules for significant figures, many students lose sight of the fact that the concept of significant figures comes from estimations in measurement. The last digit in a measurement is an estimation. How could the measurement be affected by the use of several different rulers to measure the red wire? (Different rulers could yield different readings depending on their precision.) Why is it important to use the same measuring instrument throughout an experiment? (Using the same instrument reduces the discrepancies due to manufacturing defects.) PRACTICE MEASURING Estimate one digit of uncertainty. a) 4.5 cm b) * 4.55 cm c) 3.0 cm *4.550 cm is INCORRECT while 4.52 cm or 4.58 cm are CORRECT (although the estimate is poor) By adding additional numbers to a measurement you do not make it more precise. The instrument determines how precise it can make a measurement. Remember, you can only add ONE digit of uncertainty to a measurement. In applying the rules for significant figures, many students lose sight of the fact that the concept of significant figures comes from estimations in measurement. The last digit in a measurement is an estimation. How could the measurement be affected by the use of several different rulers to measure the red wire? (Different rulers could yield different readings depending on their precision.) Why is it important to use the same measuring instrument throughout an experiment? (Using the same instrument reduces the discrepancies due to manufacturing defects.)

    29. Implied Range of Uncertainty When the plus-or-minus notation is not used to describe the uncertainty in a measurement, a scientist assumes that the measurement has an implied range, as illustrated above. The part of each scale between the arrows shows the range for each reported measurement.When the plus-or-minus notation is not used to describe the uncertainty in a measurement, a scientist assumes that the measurement has an implied range, as illustrated above. The part of each scale between the arrows shows the range for each reported measurement.

    30. A student reads a graduated cylinder that is marked at 15.00 mL, as shown in the illustration. Is this correct? NO Express the correct reading using scientific notation. 15.0 mL or 1.50 x101 mLA student reads a graduated cylinder that is marked at 15.00 mL, as shown in the illustration. Is this correct? NO Express the correct reading using scientific notation. 15.0 mL or 1.50 x101 mL

    31. Reading a Vernier

    32. Reading a Vernier Image courtesy: http://www.northerntool.com/images/product/images/558470_lg.jpgImage courtesy: http://www.northerntool.com/images/product/images/558470_lg.jpg

    36. How to Read a Thermometer (Celcius)

    37. Record the Temperature (Celcius)

    38. Measurements

    39. Using Measurements MEASUREMENT

    40. Accuracy vs. Precision Accuracy - how close a measurement is to the accepted value Precision - how close a series of measurements are to each other

    41. Percent Error Indicates accuracy of a measurement

    42. Percent Error A student determines the density of a substance to be 1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL.

    43. Significant Figures Indicate precision of a measurement. Recording Sig Figs Sig figs in a measurement include the known digits plus a final estimated digit

    44. Significant Figures Counting Sig Figs (Table 2-5, p.47) Count all numbers EXCEPT: Leading zeros -- 0.0025 Trailing zeros without a decimal point -- 2,500

    45. Significant Figures

    46. Significant Figures Calculating with Sig Figs Multiply/Divide - The # with the fewest sig figs determines the # of sig figs in the answer.

    47. Significant Figures Calculating with Sig Figs (cont) Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer.

    48. Significant Figures Calculating with Sig Figs (cont) Exact Numbers do not limit the # of sig figs in the answer. Counting numbers: 12 students Exact conversions: 1 m = 100 cm 1 in any conversion: 1 in = 2.54 cm

    49. Significant Figures 5. (15.30 g) (6.4 mL)

    50. Scientific Notation Converting into scientific notation: Move decimal until theres 1 digit to its left. Places moved = exponent. Large # (>1) ? positive exponent Small # (<1) ? negative exponent Only include sig. figs.

    51. Scientific Notation 7. 2,400,000 ?g 8. 0.00256 kg 9. 7 ? 10-5 km 10. 6.2 ? 104 mm

    52. Scientific Notation Calculating with scientific notation

    53. Proportions Direct Proportion

    54. Reviewing Concepts Measurement Why do scientists use scientific notation? What system of units do scientists use for measurements? How does the precision of measurements affect the precision of scientific calculations? List the SI units for mass, length, and temperature. Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 20 Why do scientists use scientific notation? Scientific notation makes very large or very small numbers easier to work with. What system of units do scientists use for measurements? Scientists use a set of measuring units called SI. How does the precision of measurements affect the precision of scientific calculations? The precision of a calculation is limited by the least precise measurement used in the calculation.Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 20 Why do scientists use scientific notation? Scientific notation makes very large or very small numbers easier to work with. What system of units do scientists use for measurements? Scientists use a set of measuring units called SI. How does the precision of measurements affect the precision of scientific calculations? The precision of a calculation is limited by the least precise measurement used in the calculation.

    56. Significant figures: Rules for zeros

    57. Significant Digits

    58. How to pick a lab partner

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