Chem I chapter 1 pp

8/11/2019 Chem I chapter 1 pp

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Chapter 1 Chemistry:

Matter and Measurement

General Chemistry:An Integrated Approach

Hill, Petrucci, 4th

Edition


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Chapter 1: Chemistry: Matter andMeasurement

2

Chemistry: Principles and

ApplicationsChemical theory and applications are interwovenlike the threads of a fine fabric.

Chlorine gas is an example of achemical with many applications.Understanding the theory makes forbetter use of this chemical.

The applications of chemistry, muchlike the science itself, undergoconstant change .


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3

Getting Started: Some Key Ideas

CHEMISTRYThe study of

Composition whats in it?

E.g., water is 2 parts Hydrogenand 1 part Oxygen

EOS

Properties:

E.g., boiling point, density,flammability

Structure how is it

assembled?E.g., crystals


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4

Key Ideas, cont.

Matter = anything that has mass and occupies space

ATOMS smallest distinctive unit in a sample of matter

EOS

MOLECULES largerunits of 2 or more atoms.


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5

Properties A physical property is

displayed by a sample of matterwithout undergoing any changein the composition of the matter.

Physical properties include mass,color, volume, temperature,density, melting point, etc.

Chemical property displayedby a sample of matter as itundergoes a change incomposition.

Flammability, toxicity, reactivity,acidity are all chemical properties.

Copper is red-brown, opaque,solid: physical

properties.

Ethanol is flammable:

a chemical property.


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6EOS


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7

Key Terms: Properties In a physical change , there is no

change in composition. No new substances are formed.

Examples include: evaporation;melting; cutting a piece of wood;dissolving sugar in water.

In a chemical change or chemicalreaction , the matter undergoes achange in composition.

New substances are formed. Examples include: burning gasoline;

dissolving metal in acid; spoilage offood.

The liquid fuelevaporates: a

physical change.

The vapor burns,combining with

oxygen: a

chemical change.


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Chemical Symbols

A one- or two-lettered designation derived from thename of the element

EOS

Note that the first letter is always capitalized and thesecond is lowercase

Most symbols are based on English names:Hydrogen = H Neon = Ne Chromium = Cr


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10

Chemical Symbols

In some cases, symbols come from Latin names


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12

Models

Models are tangible items orrepresentative pictures of atoms

and molecules

EOS


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13

Scientific Measurements and Units

All measurements contain two essential piecesof information:

a number (the quantitative piece)a unit (the qualitative piece)

EOS

The number 60 is somewhat meaningless

without units. Consider this for ones wages: $ per week$ per hour which is preferable?!


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Chapter 1: Chemistry: Matter andMeasurement 14

Scientific Measurements and Units

Scientists worldwide use common measurement unitscalled the International System of Units (SI)


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Common SI Prefixes

EOS

Examples:

Gigahertz (GHz)Megabytes (MB)Terawatts (TW)


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Measuring Volume

Volume units typically use the Liters base unit

Very convenient formeasuring the volume ofirregularly shapedcontainers

EOS


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Measuring Volume, cont.

EOS

Regularly shapedobjects can use a

variant of the volumeunit cubic distanceunits

e.g., m 3, cm 3, etc.


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Comparing Temperature Scales

The SI unit for temperature iskelvins (K).Note that a change of 1 C = 1 K

EOS

Some Celsius/Fahrenheitequivalents

b.p. of water 100/212

f.p. of water 0/32Room -temperature 20/68


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Precision and Accuracy in

Measurements Precision refers to how closely individual scientific

measurements agree with one another. Accuracy refers to the closeness of the average of aset of scientific measurements to the correct ormost probable value.

Sampling errors occur when a group of scientificmeasurements do not represent the entire populationof the variable being studied.

EOS


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Precision & Accuracy Illustrated

EOS


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Significant Figures

EOS

All digits in a number that are known withcertainty plus the first uncertain digit

The more significant digits obtained, the better the precision of a measurement

The concept of significant figures applies only tomeasurements

Exact values have an unlimited number ofsignificant figures


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Rules for Zeros in

Significant FiguresZeros between two other significant digits ARE significant

e.g., 1 0023A zero preceding a decimal point is not significant

e.g., 0.1 0023

EOS

Zeros between the decimal point and the first nonzerodigit are not significant

e.g., 0.001 0023


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Rules for Significant Figures

in Calculations KEY POINT: A calculated quantity can be nomore precise than the least precise data used inthe calculation

EOS

Analogy: a chain is only as strong asits weakest link

and the reported result should reflect this fact


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Significant Figuresin Calculations

Multiplication and Division: the reported results shouldhave no more significantfigures than the factor with thefewest significant figures

1.827 m 0.762 m = ?

EOS

0.762 has 3 sigfigs so thereported answer is 1.39 m 2


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A Problem-Solving Method

Chemistry problems usually require calculations,and yield quantitative (numerical) answers

For example,1 inch = 2.54 cm

EOS

The unit-conversion method is useful forsolving most chemistry problems thefocus here is on unit equivalents


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Other Equivalents andConversion Factors

A conversion factoris the fractional

expression of theequivalents

EOS

1 2.54

2.54 1

inch cmor cm inch


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Two Examples

EOS

How many cm are in 26 inches?

26 in cmin

2.541

= 66 cm


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A pure substance has a mass of

12.333 g. What substance is it? We have no earthly idea! Mass is NOT an

intensive property.

That is, mass alone is not characteristic ofthe identity of the substance.


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Density

Density is the ratio of mass perunit volume of a substance

L g or

mL g or

cm g d

areunitscommonV m

Volumemass

d

3

...

EOS


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The density of a pure substance is

calculated to be 7.78 g/cm 3. What isthis pure substance? See the Table on the next page.


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Densities of Common Substances

EOS

Note that sincedensity is a ratio, it

can also be aconversion factor

e.g., Cu is 8.94 g

1 cm 3


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Density of blood serum lipoproteins

VLDL = 1.006-1.019 g/mL 5% protein

LDL = 1.019-1.063 g/ml 25% protein

HDL = 1.063-1.21 g/mL 50% protein


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A pousse-cafe

Cognac 0.954 g/mL light brown Curacao 1.096 blue

Crme de cacao 1.123 white Crme de menthe 1.132 green Grenadine 1.343 chartreuse

Liqueurs with most alcohol and least amountof dissolved sugar are on top.


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Summary of Concepts, cont.

Matter is made up of atoms and molecules and can besubdivided into two broad categories: substances andmixtures

EOS


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Summary of Concepts

Four basic quantities of measurement: mass,length, time, and temperature

Special attention should be paid to theconcept of significant figures in reportingcalculated quantities

Precision and accuracy are importantindicators of the validity and plausibility ofa set of measurements

EOS


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Summary of Concepts

Physical properties and changes exhibit nochange in composition, only appearance

Chemical properties and changes exhibitchanges in composition quantities Many chemistry problems can be solved

using the unit-conversion method

EOS

Chem I chapter 1 pp

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