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Honors ChemistryUnit 1: Introduction to Chemistry
Science Measurement and MathSignificant Figures, SI Units, and Scientific Notation
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Honors ChemistryUnit 1: Introduction to Chemistry
Learning Objectives:
I can use task appropriate instruments to obtain accurate measurements.
I can use the language of science to represent values in a clear and accurate manner.
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BeakerSoln prep, storage, rxns
250 mL (+/- 10 mL )
Graduated CylinderVolume transfer
250 mL (+/- 1 mL )
Volumetric FlaskPrecise final vol for dilutions
250 mL (+/- 0.08 mL )
Consider 3 types of glassware for liquids:
LO: I can use task appropriate instruments to obtain accurate measurements.
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LO: I can use task appropriate instruments to obtain accurate measurements.
Accuracy vs. Precision
Accurate: WHY?!
Precise: WHY?!
Accurate and precise: WHY?!
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Confidence in Measurements
Accuracy: How close a number is to the actual value
Precision: How close the measurements are to each other; reproducible
% Error = l Experimental – Theoretical ITheoretical Value
X 100
LO: I can use task appropriate instruments to obtain accurate measurements.
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How do you determine the correct number of digits to record from a measurement?
Include: All readable digits…CertainPlus 1 estimated digits…Uncertain
An estimated digit should be included in ALL measurements taken in lab.
Number of digits in a measurement tells how CONFIDENT you are in that measurement.
LO: I can use task appropriate instruments to obtain accurate measurements.
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Include all digits with certainty plus one with uncertainty
Triple Beam Balance Mass = 2 7. 7 0 g
One digit of uncertainty
LO: I can use task appropriate instruments to obtain accurate measurements.
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Tell your neighbor what you think the length of this piece of paper is. To what place should you report the value?
11.63 cm
LO: I can use task appropriate instruments to obtain accurate measurements.
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1)To what place should the volume be reported?
2) What is the volume of liquid in the graduated cylinder?
hundredths
Volume = 21.62 mL
22
LO: I can use task appropriate instruments to obtain accurate measurements.
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LO: I can use the language of science to represent values in a clear and accurate manner.
What confidence should you have in values that you didn’t measure?
Value Sig Figs
0.0005 12.07 3400 11.0 2
9000. 40.0000703 3
Can you figure out the rules?
Significant Figures!!
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Significant Figures The Rules
1. Non-zero #’s are ALWAYS significant
2. Zeros between two non-zeros are significant
3. Decimal present: -Trailing zeros are significant (ex. 27.00 4 sig figs) -Zeros in front of the non-zeros are NOT significant (ex. 0.00345 3 sig figs)
4. Decimal absent:-Trailing zeros are NOT significant (ex. 8900 2 sig figs)
LO: I can use the language of science to represent values in a clear and accurate manner.
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Calculations w/ Significant Figures The Rules
Multiplication/Division
Limited by the value with the fewest sig figs
23.4 x 1.9 = 44.46
Addition/Subtraction
Determined by the largest digit of
uncertainty
35.78+ 67.9
103.68
= 44
2 sig figs X
= 103.6
4 sig figs
LO: I can use the language of science to represent values in a clear and accurate manner.
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LO: I can use the language of science to represent values in a clear and accurate manner.
Scientists use the SI (Système international) of measurement
-To improve communication-Convenience -Diminish likelihood of errors
Curious about how and why standardized units came to be? Learn more here: The Bitter Class Struggle Behind Our Definition of the Kilogram
https://www.theatlantic.com/science/archive/2018/10/standard-units-kilogram-tyranny/574276/
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SI Base Unit used in Chemistry:Quantity Unit Abb. Measurement
ToolLength Meter m Ruler,
meterstickMass Kilogram* kg Balance
Time Second s Stopwatch
Temperature Kelvin* K ThermometerAmount of Substance
Mole* mol NA
Current Ampere* A Ammeter
Luminous Intensity
Candela cd Photometer
LO: I can use the language of science to represent values in a clear and accurate manner.
*How we define these base units will change on World Metrology Day, May 20, 2019. Learn more here.
https://www.nature.com/news/new-definitions-of-scientific-units-are-on-the-horizon-1.22837
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All measurements have what two things?
LO: I can use the language of science to represent values in a clear and accurate manner.
Fundamental Units vs. Derived Units
Number and Unit
Function of fundamental
units
Base Units defined wrt natural
phenomenon
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LO: I can use the language of science to represent values in a clear and accurate manner.
Quantity Symbol Unit
Area A m2
Volume V m3
Velocity v m/s
Acceleration a m/s2
Wavenumber σ m-1
Density ρ kg/m3
Concentration c mol/m3
SI Derived Units expressed in terms of Base Units
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LO: I can use the language of science to represent values in a clear and accurate manner.
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LO: I can use the language of science to represent values in a clear and accurate manner.
Scientific Notation
Coefficient between1 and 10
5478.8 = 5.4788 x 10 3
base
exponent
Standard Notation Scientific Notation
93456.78
0.003467
8.327 x 107
67.00942
6.48 x 10-6
3.467 x 10-39.345678 x 104
6.700942 x 10183270000
0.00000648
123
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LO: I can use the language of science to represent values in a clear and accurate manner. Metric Prefixes Scientific Notation
Prefix Sym Multiplier Exp Norm E Giga G 1,000,000,000 109 1 x 109 1E9
Mega M 1,000,000 106 1 x 106 1E6
Kilo k 1000 103 1 x 103 1E3
Hecto h 100 102 1 x 102 1E2
Deka da 10 101 1 x 101 1E1
Base Unit (gram, meter, liter, etc.) 100 1 x 100 1E0
Deci d 0.10 10-1 1 x 10-1 1E-1
Centi c 0.01 10-2 1 x 10-2 1E-2
Milli m 0.001 10-3 1 x 10-3 1E-3
Micro m 0.000001 10-6 1 x 10-6 1E-6
Nano n 0.000000001 10-9 1 x 10-9 1E-9
Pico p 0.000000000001 10-12 1 x 10-12 1E-12
Me
mo
rize
!!!
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LO: I can use the language of science to represent values in a clear and accurate manner.
1. How many picoliters are in 1 liter?
2. How many grams are in 1 megagram?
3. How many meters are in 1 dekameter?
4. How many deciseconds are in 1 second?
1 L = 1 x 10-12 pL
1 x 102 m = 1 dam
1 x 106 g = 1 Mg
1 x 101 ds = 1 s
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Human hair ~10-50 µm
LO: I can use the language of science to represent values in a clear and accurate manner.
What is the width of a human hair in meters?
Dimensional Analysis
1. Start with what is given2. Convert to the base unit desired unit
10 µm= ? mX
1 m
106 µm
= 10-5 m
1
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LO: I can use the language of science to represent values in a clear and accurate manner.
1. Convert 4.5 ng to mg.
2. Convert 1.5 dm to hm.
Try these:
X4.5 ng
X1g
109 ng
103 mg
1 g 1
4.5 x 10-6 mg=
X1.5 dm
1X
1 m
101 dm
1 hm
102 m 1
1.5 x 10-3 hm=
1
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LO: I can use the language of science to represent values in a clear and accurate manner.
Convert 8.3 m/s to nm/ms
How about this one?
Some tips:1. Identify the conversions 2. Work one at a time3. Always check by cancelling units
X8.3 m
sX
109 nm
1 m
1 s
103 ms ms
8.3 x 106 nm=
m nm, s ms
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