chemistry

CHEMISTRY

Dr. Shyh-ching Yang

Chemistry, 6e

Steven S. Zumdahl 歐亞書局有限公司

　　　楊 士 慶

Chapter 1(a)

Chemical Chemical FoundationsFoundations

Introduction: Chemistry is around you all the time

Prof. Luis W. Alvarez solved the problem of the disappearing dinosaurs.

--- iridium 　銥　 77Ir --- niobium 鈮　 41 Nb Decline of Roman Empire --- A sweet syrup called “ Sapa” Boiling down grape juice in a lead-lined vessels, and cooled it down. It

is the reason for Sapa’s sweetness. It was “lead acetate”. Story of David & Susam --- Porphyria 一種稀有的血液疾病 Low cobalt level 27Co, could be result in personality disorder and violen

t behavior. Lithium salts have been shown to be very effective in controlling the eff

ects of manic 狂噪 depressive 憂鬱 disease.

Chemistry: A Science for the 21st Century

• Health and Medicine

• Sanitation 衛生 systems

• Surgery with anesthesia 麻醉• Vaccines 疫苗 and antibiotics 抗生素 •Energy and the Environment

• Fossil fuels

• Solar energy

• Nuclear energy

1.1

Chemistry: A Science for the 21st Century

• Materials and Technology

• Polymers, ceramics, liquid crystals

• Room-temperature superconductors?

• Molecular computing?

• Food and Agriculture

• Genetically modified crops

• “Natural” pesticides 殺蟲劑• Specialized fertilizers 肥料

1.1

（ 1.1). Chemistry: An Overview

What is matter made of ? – Atoms Very recently for the first time we can “see”

individual atoms—via STM (Scanning Tunneling Microscope)

One of the main challenges of chemistry is to understand the connection between the macroscopic world that we experience and the microscopic world of atoms and molecules.

Figure 1.01a: The surface of a single grain of table salt.

Figure 1.01b: An oxygen atom on a gallium 31Ga 鎵 arsenide 33As 砷 surface.

Figure 1.01c: Scanning tunneling microscope image showing rows of ring-shaped clusters( 串 ) of benzene molecules on a rhodium 45Rh 銠 surface.

Figure 1.2 A charged mercury atom shows up as a tiny white dot.

Figure 1.3: Sand on a beach looks uniform from a distance, but up close the irregular sand grains are visible.

Igniting soap bubbles filled with a mixture of hydrogen and oxygen.

(1.2) Steps in the Scientific Method(P.6)

1.1. ObservationsObservations

quantitative( involves both a number and a uniquantitative( involves both a number and a unit)t)

qualitativequalitative （（ does not involve a number)does not involve a number)

2.2. Formulating hypothesesFormulating hypotheses

possible explanation for the observationpossible explanation for the observation

3.3. Performing experimentsPerforming experiments

gathering new information to decidegathering new information to decide whether thwhether the hypothesis is valide hypothesis is valid

Outcomes( 結果） Over the Long-Term

Theory (Model)Theory (Model)

A set of tested hypotheses that give anA set of tested hypotheses that give an overall explanation of some natural overall explanation of some natural

phenomenon.phenomenon.

Natural LawNatural Law

The same observation applies to manyThe same observation applies to many different systemsdifferent systems

Example - Law of Conservation of massExample - Law of Conservation of mass

Law （定律） v. Theory

A A lawlaw summarizes what happens; summarizes what happens;

A A theorytheory (model) is an attempt to (model) is an attempt to explain explain whywhy it happens. it happens.

Figure 1.4: The fundamental steps of the scientific method.

Figure 1.5: The various parts of the scientific method.

Nature of Measurement

Measurement - quantitative observation Measurement - quantitative observation consisting of 2 partsconsisting of 2 parts

*Part 1 –number*Part 1 –number *Part 2 - scale (unit)*Part 2 - scale (unit)

Examples:Examples:

* 20 grams* 20 grams * 6.63 * 6.63 Joule seconds Joule seconds

(1.3) Unit of Measurement

International System

Based on metric system and units derived Based on metric system and units derived （取得）（取得） from metric systefrom metric systemm..

Chemistry In Action

On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mar’s atmosphere 100 km lower than planned and was destroyed by heat.

1.7

1 lb = 1 N

1 lb = 4.45 N

“This is going to be the cautionary tale that will be embedded （深留腦中） into introduction to the metric system in elementary school, high school, and college science courses till the end of time.”

1.7

Figure 1.6: Measure-ment of volume

Figure 1.7: Common types of laboratory equipment used to measure liquid volume.

Figure 1.8: An electronic analytical balance.

Figure 1.9: Measurement of volume using a buret. The volume is read at the bottom of the liquid curve (called the meniscus(新月 ).

(1.4) Uncertainty in Measurement

A digit that must be A digit that must be estimatedestimated is is called called uncertainuncertain. A . A measurementmeasurement always has some degree of always has some degree of uncertainty.uncertainty.

Figure 1.10: The results of several dart throws show the difference between precise （精確） and accurate （準確） .

Accuracy – how close a measurement is to the true value

Precision – how close a set of measurements are to each other

accurate&

precise

precisebut

not accurate

not accurate&

not precise

1.8

1.8

Scientific NotationThe number of atoms in 12 g of carbon:

602,200,000,000,000,000,000,000

6.022 x 1023

The mass of a single carbon atom in grams:

0.0000000000000000000000199

1.99 x 10-23

N x 10n

N is a number between 1 and 10

n is a positive or negative integer

Scientific Notation

1.8

568.762

n > 0

568.762 = 5.68762 x 102

move decimal left

0.00000772

n < 0

0.00000772 = 7.72 x 10-6

move decimal right

Addition or Subtraction

1. Write each quantity with the same exponent n

2. Combine N1 and N2 3. The exponent, n, remains

the same

4.31 x 104 + 3.9 x 103 =

4.31 x 104 + 0.39 x 104 =

4.70 x 104

Scientific Notation

1.8

Multiplication

1. Multiply N1 and N2

2. Add exponents n1 and n2

(4.0 x 10-5) x (7.0 x 103) =(4.0 x 7.0) x (10-5+3) =

28 x 10-2 =2.8 x 10-1 Division

1. Divide N1 and N2

2. Subtract exponents n1 and n28.5 x 104 ÷ 5.0 x 109 =

(8.5 ÷ 5.0) x 104-9 =1.7 x 10-5

Precision （精密度） and Accuracy（準確度）

Accuracy Accuracy refers to the agreement of a refers to the agreement of a particular value with theparticular value with the truetrue value.value.

PrecisionPrecision refers to the degree of refers to the degree of agreement among several elements of the agreement among several elements of the same quantity.same quantity.

Types of Error

Random Error Random Error (Indeterminate(Indeterminate 不能不能確定的 確定的 Error) - measurement has an equError) - measurement has an equal probability of being high or low.al probability of being high or low.

Systematic Error Systematic Error (Determinate Erro(Determinate Error) - Occurs in the r) - Occurs in the same directionsame direction each timeach time (high or low), often resulting from poor te (high or low), often resulting from poor technique.echnique.

(1.5) Significant Figures and Caculations:Rules for Counting Significant Figures - Overview

1.1. Nonzero integersNonzero integers 2.2. ZerosZeros leading zeros( does not count as leading zeros( does not count as

significant figures) ex. 0.0025 ( 2 sig.)significant figures) ex. 0.0025 ( 2 sig.) captive (captive ( 中間）中間） zeroszeros　　 (yes) ex. 1.008 ( 4sig.) (yes) ex. 1.008 ( 4sig.) trailing(trailing( 尾數）尾數） zeroszeros　　 ex. 100 (1 sig.); 100.(3 sig.)ex. 100 (1 sig.); 100.(3 sig.) 1.00*10**2 (3 sig.)1.00*10**2 (3 sig.) 　　 3.3. Exact numbers(Exact numbers( 精確數精確數

字）字）

Rules for Counting Significant Figures - Details

Nonzero integersNonzero integers always count as always count as significant figures.significant figures.

3456 3456 has has 4 4 sig figs.sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros Leading zerosLeading zeros do not count as do not count as

– significant figures.significant figures.

0.04860.0486 has has 33 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros Captive zerosCaptive zeros always count as always count as

– significant figures.significant figures.

16.07 16.07 hashas 4 4 sig figs.sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros Trailing zerosTrailing zeros are significant only are significant only

– if the number contains a dif the number contains a decimal pointecimal point （小數點）（小數點） ..

9.3009.300 has has 44 sig figs. sig figs.

Rules for Counting Significant Figures - Details

Exact numbersExact numbers have an infinite have an infinite number of significant figures.number of significant figures.

11 inch = inch = 2.54 2.54 cm, exactlycm, exactly

Significant Figures

1.8

•Zeros between nonzero digits are significant

•Any digit that is not zero is significant

1.234 kg 4 significant figures

606 m 3 significant figures

•Zeros to the left of the first nonzero digit are not significant

0.08 L 1 significant figure

•If a number is greater than 1, then all zeros to the right of the decimal point are significant

2.0 mg 2 significant figures

•If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant

0.00420 g 3 significant figures

How many significant figures are in each of the following measurements?

3001 g 4 significant figures

0.0320 m3 3 significant figures

6.4 x 104 molecules 2 significant figures

560 kg 2 significant figures

1.8

24 mL 2 significant figures

Significant Figures

1.8

Addition or Subtraction

The answer cannot have more digits to the right of the decimalpoint than any of the original numbers.

89.3321.1+

90.432 round off to 90.4

one significant figure after decimal point

3.70-2.91330.7867

two significant figures after decimal point

round off to 0.79

Significant Figures

1.8

Multiplication or DivisionThe number of significant figures in the result is set by the original number that has the smallest number of significant figures

4.51 x 3.6666 = 16.536366 = 16.5

3 sig figs round to3 sig figs

6.8 ÷ 112.04 = 0.0606926

2 sig figs round to2 sig figs

= 0.061

Significant Figures

1.8

Exact Numbers( 精確數字）Numbers from definitions or numbers of objects are consideredto have an infinite number of significant figures

The average of three measured lengths; 6.64, 6.68 and 6.70?

6.64 + 6.68 + 6.703

= 6.67333 = 6.67

Because 3 is an exact number

= 7

Rules for Significant Figures in Mathematical Operations

Multiplication and Division: Multiplication and Division: # sig figs # sig figs in the result equals the number in the least in the result equals the number in the least precise measurement used in the precise measurement used in the calculation.calculation.

6.38 6.38 2.0 = 2.0 =12.76 12.76 13 (2 sig figs)13 (2 sig figs)

Rules for Significant Figures in Mathematical Operations

Addition and Subtraction: Addition and Subtraction: # sig fig# sig figs in the result equals s in the result equals the number of decthe number of decimal(imal( 小數點小數點 ) places in the least precis) places in the least precisee measurement. measurement.

66.8.8 + 11.934 = + 11.934 = 18.734 18.734 18.7 18.7 (3 sig figs) (3 sig figs)

(1.6)Dimensional Analysis

Proper use of “unit factors” leads to Proper use of “unit factors” leads to proper units in your answer.proper units in your answer.

(1.7)Temperature

Celsius scale =Celsius scale =CCKelvin scale =Kelvin scale =KKFahrenheit scale =Fahrenheit scale =FF

Figure 1.11: The three major temperature scales.

Figure 1.12: Normal body temperature on the Fahrenheit, Celsius, and Kelvin scales.

Temperature

(1.8)Density

Density Density is the mass of substance per is the mass of substance per unitunit

volume of the substance:volume of the substance:

MatterMatter （物質）（物質） :: Anything occupying sp Anything occupying space and having mass.ace and having mass.

(1.9) Classification of Matter

Three States of Matter:Three States of Matter:

– Solid: rigid - fixed volume and shapeSolid: rigid - fixed volume and shape

– Liquid: definite volume but assumes Liquid: definite volume but assumes the shape of its containerthe shape of its container

– Gas: no fixed volume or shape – Gas: no fixed volume or shape – assumes the shape of its containerassumes the shape of its container

Figure 1.13: The three states of water (where red spheres represent oxygen atoms and blue spheres represent hydrogen atoms).

Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

AA homogeneous mixture(homogeneous mixture( 均勻混合物）均勻混合物）is a solution(for example, vinegaris a solution(for example, vinegar 食用醋食用醋 ))

AA heterogeneous mixtureheterogeneous mixture （不（不均勻混合均勻混合物物 is, to the naked eye, clearly not uniform (fois, to the naked eye, clearly not uniform (for example, a bottle of dressing)r example, a bottle of dressing)

Pure Substances

Can be isolated by separation Can be isolated by separation methods:methods:

ChromatographyChromatography FiltrationFiltration DistillationDistillation

Figure 1.14: Simple laboratory distillation apparatus.

Figure 1.15a: Paper chromatography of ink. (a) A line of the mixture to be separated is placed at one end of a sheet of porous paper.

Figure 1.15b: Paper chromatography ( 層析） of ink. (b) The paper acts as a wick （燈心） to draw up the liquid.

Figure 1.15c: Paper chromatography of ink.

(c) The component with the weakest attraction for the paper travels faster than the components that cling （吸住） to the paper.

ElementElement （元素）（元素） :: A substance that cannot bA substance that cannot be decomposed into simpler substances by chee decomposed into simpler substances by chemical means.mical means.

Compound(Compound( 化合物）化合物） :: A substanceA substance （物質） （物質） wiwith a constant composition that can be broken down th a constant composition that can be broken down into elements by chemical processes.into elements by chemical processes.

The element mercury (top left) combines with the element iodine (top right) to form the compound mercuric iodide (bottom). This is an example of a chemical change.

Figure 1.16: The organization of matter.

25. How many significant figures are in each of the following?

3

5

.12

.1098

.2001

.2.001 10

.0.0000101

.1.01 10

.1000.

.22.04030

a

b

c

d

e

f

g

h

26. How many significant figures are in each of the following?

2

3

3

3

.100

.1.0 10

.1.00 10

.100.

.0.0048

.0.00480

.4.80 10

.4.800 10

a

b

c

d

e

f

g

h

27. Round off each of the following numbers to three significant figures, and write the answer in standard exponential notation.

3

.312.54

.0.00031254

.31,254,000

.0.31254

.31.254 10

a

b

c

d

e

28. Use exponential notation to express the number 480 to

one significant figure. two significant figures. Three significant figures. four significant figures.

29. Perform the following mathematical operations, and express each result to the correct number of significant figures.

A. 97.381+4.2502+0.99195B. 171.5+72.915-8.23C. 1.00914+0.87104+1.2012D. 21.901-13.21-4.0215

30. Perform the following mathematical operations, and express each result to the correct number of significant figures.

23

4 3 2

6

7

0.102 0.0821 273.

1.01

.0.14 6.022 10

.4.0 10 5.021 10 7.34993 10

2.00 10.3.00 10

a

b

c

d

66. Classify each of the following as homogeneous or heterogeneous.

A. Soil B. the atmosphere C. a carbonated soft drink D. gasoline E. gold F. a solution of ethanol and water

68. Classify each of the following as a mixture or a pure substance

A. Water B. Blood C. The Ocean D. Iron E. Brass F. Uranium G. Wine H. Leather I. Table Salt