RegentsRegentsChemistryChemistry

Tyna L. MeeksTyna L. Meeks

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MeasurementMeasurement

What is the PURPOSE of measuring/measurements?

1) Why is there a need to measure things?

2) Is there a need to standardize measurements?

3) Who decides on the standards?

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MeasurementMeasurement

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…

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MeasurementMeasurement

Taking proper medicine….

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MeasurementMeasurement

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.

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MeasurementMeasurement

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

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MeasurementMeasurement

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?

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MeasurementMeasurement

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.

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MeasurementMeasurement

Keeping yourself warm or cool.

Understanding weight.

Proper use of capacity.

Telling time.

Transportation.

Structure.

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MeasurementMeasurement

Standardized Measurements?

Subjective Measurement?

Objective Measurement?

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MeasurementMeasurement

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…

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MeasurementMeasurement

Standardized Measurements?

Can I interest you in a grave of chocolate?

Perhaps a piece of land, 2 square smoots?

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MeasurementMeasurement

Standardized Measurements?

Can I interest you in 1000 lbs of chocolate?

Perhaps a piece of land, 2 square Harvard Bridges?

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MeasurementMeasurement

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

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MeasurementMeasurement

Metric System

K H D u d c m

Base Units

Derived Units

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Base UnitsBase Units

This list has the current definitions of each of the This list has the current definitions of each of the seven base units…seven base units…

Length - Meter ( m )Length - Meter ( m ) Mass - Kilogram ( kg )Mass - Kilogram ( kg ) Time - Second ( s )Time - Second ( s ) Electric Current - Ampere ( A )Electric Current - Ampere ( A ) Temperature - Kelvin ( K )Temperature - Kelvin ( K ) Amount of a Substance - Mole ( mol )Amount of a Substance - Mole ( mol ) Luminous Intensity - candela ( cd )Luminous Intensity - candela ( cd )

Derived UnitsDerived Units

This list has the current definitions of each of the This list has the current definitions of each of the seven base units…seven base units…

Pressure - Pascal ( Pa ) – kg/m·sPressure - Pascal ( Pa ) – kg/m·s22 Force - Newton ( N ) - m·kg/sForce - Newton ( N ) - m·kg/s22

Energy - Joule ( J ) – kg·mEnergy - Joule ( J ) – kg·m2/s2/s22 Density – g/mL or g/cmDensity – g/mL or g/cm33 Volume – mVolume – m33

Quality of MeasurementsQuality of MeasurementsHow do we know we have good

measurements?

1) 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?

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Quality of Measurements Quality of Measurements How do we know we have good

measurements?

4) What are significant figures?

5) How do I perform order of operations with significant figures?

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Significant FiguresSignificant FiguresAll measurements are inaccurate intrinsicallymeasured quantities are reported such that the last figure is uncertain…

Precision and AccuracyPrecision and AccuracyPrecision - how closely individual measurements agree

Accuracy- how closely the measurements agree with the true value

Quality of Measurements Quality of Measurements 28

Good PrecisionPoor Accuracy

Good PrecisionGood Accuracy

Poor PrecisionPoor Accuracy

Quality of Measurements Quality of Measurements 29

Percent Error:

(accepted value - measured value) *100 accepted value

Factor Label MethodFactor Label MethodHow do we convert between units?

1) How do we convert between prefixes using the metric system?

2) How do we convert between units that are NOT metric?

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Factor Label MethodFactor Label Method• 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.?

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50 mi.50 mi. 1 hour1 hour 5280 ft5280 ft 12 in.12 in. = = inin1 hour1 hour 3600 sec.3600 sec. 1 mi.1 mi. 1 ft1 ft sec.sec.

Factor Label MethodFactor Label MethodDetermine the length in kilometers of a 500.0 mi

automobile race, knowing that 1.61 km equals 1 mile

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