chapter1 - matter

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

chapter1 - matter

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