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7/25/2019 Chapter1 - Matter
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Learning outcomes:
Distinguish among elements, compounds, and mixtures.
Identify symbols of common elements.
Identify common metric prefixes.
Demonstrate the use of significant figures, scientific notation, and SI units in
calculations.
Att ach appr opr iate SI uni ts to defi ned quanti ties, and employ dimensional analysis in
calculations
Chapter 1Introduction: Matter and Measurement
Scientific
Method
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Atomic and Molecular Perspective
Chemistry The study of properties and behavior of matter.
Matter Anything that has mass and occupies space.
Atom The smallest stable building block of matter. Made upof protons, neutrons & electrons.
Molecule Groups of atoms held together with a specificconnectivity and shape.
EthanolStoichiometry = C2H6O
Melting Point = -115 CBoiling Point = 78 C
Density = 0.79 g/cm3
Chemical Prop. = Intoxicating
Ethylene GlycolStoichiometry = C2H6O2Melting Point = -16 C
Boiling Point = 197 C
Density = 1.11 g/cm3
Chemical Prop. = Toxic
Dimethyl EtherStoichiometry = C2H6O
Melting Point = -140 C
Boiling Point = -24 C
Density = Gas
Chemical Prop. = Intermediate
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Physical States of Matter
Types:1. Gas (vapor)2. Liquid3. Solid
Elements, Compounds & MixturesPure Substance Matter that has a fixed composition and distinct properties. Allsubstances are either elements or compounds.
Elements All atoms are the same kind, elements have only one type of atom. e.g.oxygen (O2), gold (Au), silicon (Si) and diamond (C).
Compounds Contains more than one type of atom, but all molecules (or repeatunits) are the same, e.g. water (H2O), ethanol (C2H6O), quartz (SiO2), sodiumchloride (NaCl).
Mixture Have variable composition and can be separated into component parts byphysical methods. Mixtures contain more than one kind of molecule, and theirproperties depend on the relative amount of each component present in the mixture.
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Periodic Table
Know the names and symbols forthese groups and common elements
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Compound
Elements
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Homogeneous & Heterogeneous Mixtures
Heterogeneous Mixture - Composition andproperties are non-uniform.
Chocolate Chip Cookie Chocolate, Dough, etc.
Concrete Cement, Rocks, etc.
Nachos Chips, cheese, jalapeos, salsa, etc.
Homogeneous Mixture - Composition andproperties are uniform. Sometimes called a solution.
Air principle components include O2, N2 & CO2
Vodka principle components are ethanol and water
Brass solid solution of Cu and Zn
Ruby solid solution of Al2O3 and Cr2O3
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Chemical and Physical PropertiesPhysical Properties Some properties can be readily measured
with our senses, e.g. odor and color, instruments are needed tomeasure other properties, such as electrical resistivity, hardness,melting point, boiling point, density, mass, volume, etc.
Chemical Properties Describe the reactivity of a substancetoward other substances. Examples include:
Ethanol burns in air (reacts with oxygen in the air)Sodium reacts vigorously with water,Corrosion of metal parts (rust),Trinitrotoluene (TNT) is explosive,
Properties of Matter
Intensive Properties:
Independent of the amount of thesubstance that is present.
Density, boiling point, color, etc.
Extensive Properties:
Dependent upon the amount of the
substance present. Mass, volume, energy, etc.
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Separation of Mixtures
Filtration Distillation
Column Chromatography
1 inch = 2.54 cm
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Temperature Scales
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Temperature
The Fahrenheitscale is not used inscientificmeasurements.
F = 9/5(C) + 32
C = 5/9(F 32)
The 9/5, 5/9, and32 are exact
numbers and do notinfluence significantfigures.
Temperature The Kelvin is the
SI unit oftemperature.
It is based on theproperties ofgases.
There are nonegative Kelvintemperatures.
K = C + 273.15
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Volume
Volumetric Glassware
Uncertainty in Measurements - Differentmeasuring devices have different usesand different degrees of precision.
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Densitymass per unit volume Density=
massvolume
Precision and Accuracy Precision is a measure of how closely individualmeasurements to agree with one another.
Accuracy refers to how closely individualmeasurements agree with the correct true value.
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Digital Reading Scale read by eye
Uncertainty and significant figures in a measurement
Significant Figures The term significant figures refers to digits
that were measured.
When rounding calculated numbers, we payattention to significant figures so we do notoverstate the accuracy of our answers.
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Significant Figures1. Zeros between non-zero numbers are always
significant.2. Zeros at the beginning of a number are never
significant, merely indicate the positon of thedecimal point.
3. Zeros at the end of the number after a decimalplace are significant if the number contains adecimal point.
4. Zeros at the end of a number before a decimalplace are ambiguous (e.g. 23,800 g), unless a
decimal point is written at the end (i.e. 23,800. g).Assume the zeros are insignificant, unless there is adecimal point.
How many significant figures are present ineach of the measured quantities?
Significant Figures
0.0012
108
2006
900.0
3.0012
0.002070
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After determining the appropriate number ofsignificant figures, round off your final answer.
1. If the first digit you drop is greater than 5, add 1to the last digit you keep. You are rounding up.
2. If the first digit you drop is less than 5, donothing to the digits you keep. You are roundingdown.
3. If the digit you drop is 5, and there are nofollowing digits, round down. If there are digits
following the 5, round up.
Rounding*
*You may receive a different rule #3 from your lab instructor.
Significant Figures & Calculations
Addition and Subtraction
Line up the numbers at the decimal point and theanswer cannot have more decimal places than themeasurementwith the fewest number of decimalplaces.
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Addition and Subtraction
The absolute uncertainty can be nosmaller than the least accurate number.
12.04
- 10.4
1.64 1.6
The answer should have no more decimal
places than the least accurate number.
3121 x 12 = 37452
Multiplication and Division
2
37452
2# sig. digits 4
= 3.7 x 104
The answer cannot have more significantfigures than the measurement with thefewest number of significant figures.
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Mixed OperationsDetermine accuracy in the same order as themathematical operations, # of significant digits in blue
but, retain at least one additional digit past thesignificant figures in combined operations, so roundingdoesnt affect results
-keep track of the proper significant figures to use atthe end.
d =2.79 g
8.34 mL - 7.58 mLv
m 2.79 g
0.76 mL=
33
3 3
2
2
d = 3.7 g/mL
=
Evaluate each expression to the correct
number of significant figures.(a) 4.184 100.620 (25.27 - 24.16) = 467
(b)
(c)
(d) 320.75 - (6102.1/3.1) = -1.6 x 103
8.925 - 8.904 100%
8.925
9.6 x 100.65
8.321+ 4.026
= 0.24%
= 1.2 x 102
Retain at least one additional digit past thesignificant figures in combinedoperations, sorounding doesnt affect results
-but keep track of the proper significant figuresfor the final answer.
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Dimensional Analysis
Units are multiplied together or divided intoeach other along with the numerical values. Keep track of both numerical values and units.
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Conversions
What is the volume of 7.20 g Ti?
1 c m
g
3
4 5 0.
7.20 g Ti x = 1.60 cm3 Ti
The density of Ti is 4.50 g/cm3
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Using Unit Conversions
Express a volume of 1.250 L in mL, cm3, and m3
110-6 m3
1 cm31,250 cm3 x = 1.250 x 10-3 m3
1 L
1000 mL1.250 L x = 1,250 mL
1 L
1000 cm31.250 L x = 1,250 cm3