Index

Measured Values• Conversion Factors

• Percent Error

• Deviations

Index

Scientific Notation

Index

Index

Measured Values• Accuracy of a measurement is

the closeness of the measurement to the true value.• Precision refers to the

reproducibility within a group of measurements.

IndexPrecision, Accuracy and Error

• Accuracy = % Error

= 100 X (Experimental – Actual)

Actual Value

• Precision = % Deviations

= 100 X ( ave. deviation)

mean

deviation = l measured – mean l

Index

Measuring values

More Precise

Index

Measured Values: Precision

• Significant Digits (means MEASURED)

–ALL Numbers are important

–need Rules to know how many to write

IndexSig Fig Rules 1. 4567

2. 34.989

3. 0.006040

4. 45.0387

5. 2.00

6. 34.900

7. 5000

8. 0.00783

9. 900.

10. 45078

IndexSig Fig Rules : multiply and divide

Answer has same number of significant digits as the number with the least significant digits.

Ex. 12.65 x 42.1 = 532.565

XX

=533

4 3

3

Index

RULES: ADD AND SUBTRACT

decimal place determines the number of digits.

The last COMMON decimal place is the last number you can justify

Ex. 10.13

+ 20.5

30.63X

= 30.6

Index

Index

Dimensional What?Dimensional What? AnalysisAnalysis

Index

DIMENSIONAL ANALYSIS

UV radiation is very energetic and causes your skin to burn. If you are exposed to 1.00 Mole of photons with a wavelength of 305. nm, what amount of energy (in kilojoules per mole) are you being hit by?

Speed of light = 2.998 x 108 m/sPlank’s Constant = 6.626 x 10-34 J s

Index

There’s more?There’s more? MetricsMetrics

IndexTypes of Observations and Types of Observations and MeasurementsMeasurements

• We make We make QUALITATIVEQUALITATIVE observations of reactions — observations of reactions — changes in color and physical changes in color and physical state.state.

• We also make We also make QUANTITATIVE QUANTITATIVE MEASUREMENTSMEASUREMENTS, which involve , which involve numbersnumbers..

• Use Use SI unitsSI units — based on the — based on the metric systemmetric system

Index

UNITS OF MEASUREMENTUNITS OF MEASUREMENTUse Use SI unitsSI units — based on the — based on the

metric systemmetric system

Length Length

MassMass

TimeTime

TemperatureTemperature

Meter, mMeter, m

Kilogram, kgKilogram, kg

Seconds, sSeconds, s

Celsius degrees, ˚CCelsius degrees, ˚Ckelvins, Kkelvins, K

Index

Units of LengthUnits of Length• 1 kilometer (km) = ? meters (m)1 kilometer (km) = ? meters (m)

• 1 meter (m) = ? centimeters (cm)1 meter (m) = ? centimeters (cm)

• 1 centimeter (cm) = ? millimeter (mm)1 centimeter (cm) = ? millimeter (mm)

• 1 nanometer (nm) = 1.0 x 101 nanometer (nm) = 1.0 x 10-9-9 meter meter

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm

Index