1 Regents Chemistry Tyna L. Meeks

Measurement 2 What is the PURPOSE of measuring/measurements? Why is there a need to measure things? 2) Is there a need to standardize measurements? 3) Who decides on the standards?

Measurement 3 Measurements are so often taken for granted we sometimes do not appreciate the grand importance measurements play in our lives. On a baseline level, measurements fall into the categories of weight, area, volume, length and even temperature. While we look at these various categories as stoic forms of mathematical measurements a closer examination of things we do in everyday life reveals their clear importance… 3

Measurement 4 Taking proper medicine…. 4

Measurement 5 Taking proper medicine…. If you have an illness (whether serious or minor) you need to take your medicine and take it in the proper amount. If you take too little or too much then you are not going to get the proper benefit from it. 5

Measurement 6 Cooking properly. Cooking of all forms is based on proper attention to measurement. 6

Measurement 7 Cooking properly. Cooking of all forms is based on proper attention to measurement. Can you bake a chicken at 600 degrees? Well, you can but the results would be pretty catastrophic! Could you may a cup of tea by dipping a tea bag into a teaspoon of warm water? 7

Measurement 8 Purchasing clothes. Now, how important could measurements be when selecting clothes? Playing sports… you really need to be accurate and comes from a clear sense of depth and distance. Making estimations. Often we do not have an exact answer so we need to make an estimation which is essentially a guess of measurement. 8

Measurement 9 Keeping yourself warm or cool. Understanding weight. Proper use of capacity. Telling time. Transportation. Structure. 9

Measurement 10 Standardized Measurements? Subjective Measurement? Objective Measurement? 10

Measurement 11 Standardized Measurements? Subjective Measurement : an observation which cannot be seen or is describing an idea, thought, or opinion Objective Measurement : an observation that can be seen, felt, heard, smelled… 11

Measurement 12 Standardized Measurements? Can I interest you in a grave of chocolate? Perhaps a piece of land, 2 square smoots? 12

Measurement 13 Standardized Measurements? Can I interest you in 1000 lbs of chocolate? Perhaps a piece of land, 2 square Harvard Bridges? 13

Measurement 14 Standardized Measurements? Can I interest you in a grave of chocolate? Perhaps a piece of land, 2 square smoots? International Union of Pure and Applied Chemistry… IUPAC 14

Measurement 15 Metric System K H D u d c m Base Units Derived Units 15

Base Units This list has the current definitions of each of the seven base units… Length - Meter ( m ) Mass - Kilogram ( kg ) Time - Second ( s ) Electric Current - Ampere ( A ) Temperature - Kelvin ( K ) Amount of a Substance - Mole ( mol ) Luminous Intensity - candela ( cd )

Derived Units This list has the current definitions of each of the seven base units… Pressure - Pascal ( Pa ) – kg/m·s2 Force - Newton ( N ) - m·kg/s2 Energy - Joule ( J ) – kg·m2/s2 Density – g/mL or g/cm3 Volume – m3

Quality of Measurements 18 How do we know we have good measurements? What is the difference between accuracy and precision? 2) How do I read instruments to the correct precision? 3) How do I determine how accurate my measurement is? 18

Quality of Measurements 19 How do we know we have good measurements? 4) What are significant figures? 5) How do I perform order of operations with significant figures? 19

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Quality of Measurements 27 Significant Figures All measurements are inaccurate intrinsically measured quantities are reported such that the last figure is uncertain… Precision and Accuracy Precision - how closely individual measurements agree Accuracy- how closely the measurements agree with the true value 27

Quality of Measurements 28 Good Precision Poor Accuracy Good Precision Good Accuracy Poor Precision Poor Accuracy 28

Quality of Measurements 29 Percent Error: (accepted value - measured value) *100 accepted value 29

Factor Label Method 30 How do we convert between units? How do we convert between prefixes using the metric system? 2) How do we convert between units that are NOT metric? 30

Factor Label Method 31 50 mi. 1 hour 5280 ft 12 in. = in Use Units throughout the calculation (helps “guide” calculation. Should always yield the proper units Uses conversion factors How fast is 50 mph in in/sec.? 50 mi. 1 hour 5280 ft 12 in. = in 1 hour 3600 sec. 1 mi. 1 ft sec. 31

Factor Label Method 32 Determine the length in kilometers of a 500.0 mi automobile race, knowing that 1.61 km equals 1 mile 32