Ch. 1: Chemical Foundations · Chemistry: An Overview

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Ch. 1: Chemical Foundations

· Chemistry: An Overview

What is matter made of ?

The Nobel Prize in Physics 1986

L: Heinrich Rohrerb(b1933) ,

R: Gerd Binnig(1947),

IBM Zurich Research Laboratory Rüschlikon, Switzerland

Scanning Tunneling Microscope (STM)

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Figure 1.01a: The surface of a single grain of

table salt.

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Figure 1.01b: An oxygen atom on a gallium

arsenide surface.

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Figure 1.01c: Scanning tunneling microscope image showing rows of ring-shaped clusters of

benzene molecules on a rhodium surface.

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Figure 1.2: A charged mercury atom shows up as a

tiny white dot.

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

are visible.

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Oxygen atom, hydrogen atom, water molecule

＊ Substances are made of ~100 atoms

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Water turning to oxygen and hydrogen

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Oxygen and hydrogen becoming water

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Figure 1.4: The fundamental steps of the scientific method.

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Steps in the Scientific Method

1.1. ObservationsObservations

quantitativequantitative

qualitativequalitative

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 the hypothesis is validwhether the hypothesis is valid

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Outcomes 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 overall explanation of some

natural 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 Example - Law of Conservation of MassMass

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Law vs. 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.

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Figure 1.5: The various parts of the scientific method.

However, we tend to see what we expect to see and often fail to notice things that we do not expect. Thus the theory we are testing helps us because it focuses our questions. However, this focusing process may limit our ability to see other possible explanation.

It is also important to keep in mind that scientists are human. They have prejudices; they misinterpret data; they become emotionally attached to their theory and thus lose objectivity; and they play politics. Science is affected by profit motives, budgets, fads, wars, and religious beliefs. The scientific methods are only as effective as the humans using them. They do not automatically lead to progress.

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Nature of Measurement

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

Part 1 - numberPart 1 - number Part 2 - scale (unit)Part 2 - scale (unit)

Examples:Examples:20 grams20 grams

6.63 6.63 Joule seconds Joule seconds

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International System

Based on metric system and units Based on metric system and units derived from metric system.derived from metric system.

English System

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The Fundamental SI Units

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Figure 1.6: Measurement of volume

1 liter = 1000 cm3

= 1000 mL

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

volume.

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Figure 1.8: An electronic analytical balance.

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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.

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

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Precision and Accuracy

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

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

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Figure 1.10: The results of several dart throws show the difference between precise

and accurate.

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Types of Error

Random Error Random Error (Indeterminate Error) - (Indeterminate Error) - measurement has an equal probability of measurement has an equal probability of being high or low.being high or low.

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

Type of Errors:(1). Determinate (or systematic) error: Can be detected, measured, and eliminated; affect the accuracy of results.

1. Instrument errors -Calibration2. Method errors

-Analysis of standard samples-Independent analysis-Blank determinations-Variation in sample size

3. Personal errors-Care and self-discipline

(2). Indeterminate (or random) errors: Cannot predict exactly a results from examination of other results; affect the precision of measurement.

-Overall uncertainty.

Precision and Accuracy (exercise 1.2)

Volume shown by Volume shown

Trial graduated cylinder by the buret

-------------------------------------------------------------------------- 1 25 mL 26.54 mL 2 25 mL 26.51 mL 3 25 mL 26.60 mL 4 25 mL 26.49 mL 5 25 mL 26.57 mL

Average 25 mL 26.54 mL

Results: Good precision for a graduated cylinder.This graduated cylinder is not very accurate. It has systematic error.

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Significant Figures and Calculations

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Rules for Counting Significant Figures - Overview

1.1. Nonzero integersNonzero integers

2.2. ZerosZeros

leading zerosleading zeros

captive zeroscaptive zeros

trailing zerostrailing zeros

3.3. Exact numbersExact numbers

Exact numbers were determined by counting, not Exact numbers were determined by counting, not obtained from measurement. obtained from measurement.

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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.

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ZerosZerosLeading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.04860.0486 has has

33 sig figs. sig figs.

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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.

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ZerosZeros Trailing zerosTrailing zeros are significant only are significant only

if the number contains a decimal if the number contains a decimal point.point.

9.3009.300 has has

44 sig figs. sig figs.

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

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

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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 in the result equals the number in the least precise measurement used in the least 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)

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Rules for Significant Figures in Mathematical Operations

Addition and Subtraction: Addition and Subtraction: # sig figs in the # sig figs in the result equals the number of decimal places result equals the number of decimal places in the least precise measurement.in the least precise measurement.

6.8 + 11.934 =6.8 + 11.934 =

18.734 18.734 18.7 (3 sig figs)18.7 (3 sig figs)

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Dimensional Analysis

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

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Temperature

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

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Temperature

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Density

Density Density is the mass of substance per unitis the mass of substance per unit

volume of the substance:volume of the substance:

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Matter:Matter: Anything occupying Anything occupying

space and having mass.space and having mass.

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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 the Liquid: definite volume but assumes the shape of its containershape of its container

Gas: no fixed volume or shape - assumes Gas: no fixed volume or shape - assumes the shape of its containerthe shape of its container

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

represent hydrogen atoms).

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Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

AA homogeneous mixturehomogeneous mixture is a solution (for is a solution (for example, vinegar)example, vinegar)

AA heterogeneous mixtureheterogeneous mixture is, to the naked eye, is, to the naked eye, clearly not uniform (for example, a bottle of clearly not uniform (for example, a bottle of ranch dressing)ranch dressing)

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Figure 1.14: Simple laboratory distillation apparatus.

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Pure Substances

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

ChromatographyChromatography

FiltrationFiltration

DistillationDistillation

CrystalizatiomCrystalizatiom

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Element:Element: A substance that cannot be A substance that cannot be decomposed into simpler substances by decomposed into simpler substances by chemical means.chemical means.

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes.

分離的分類（以物質狀態）：

固體 - 固體混合物：

固體 - 液體混合物：

固體 - 氣體混合物：

液體 - 液體混合物：

氣體 - 氣體混合物：

分離的分類（以方法）：

利用大小的差異：利用薄膜：

利用相的變化：其他分離方法 :

利用化學性親和力：

利用色層分離：分離科學，楊思廉審定，銀禾文化出版。

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利用大小的差異：過濾

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利用大小的差異：

利用相的變化：

利用化學性親和力：（ A ）溶劑 ( 媒）萃取（ like dissolves like）

液體 - 液體萃取 :

超臨界流體（ Supercritical fluid) 萃取 :

de-caffeine, proteins, vitamin

Solvent of Green (sustainable) Chemistry

(B) 吸附 ( 液體 - 固體、氣體 - 固體）：吸附劑：活性炭、矽膠、粘土、沸石、陰陽離子交換樹脂

色層分離 (chromatography separation)

移動相固定相方法

氣體固體，液體 GSC, GLC 氣相體色層分離

液體固體，液體 LC 液相色層分離

超臨界流體固體，液體 SFC 超臨界流體色層分離

對掌性異構物 (enantiomers):具有相同的物性及化性

（乳酸）

對掌性 (Chiral) 的重要性

N

O

ONH

O

O

*

thalidomide

R formS formR formS form

鎮靜效果畸胎原

Different biological effect

(沙利竇邁 )

Taste and absolute configuration of some amino acids---------------------------------------------------------------Amino acid Taste/enantiomer

D-form L-form----------------------------------------------------------------Asparagine sweet tastelessHistidine sweet tastelessIsoleucine sweet bitterLeucine sweet bitterTryptophan sweet tastelessTyrosine sweet bitter-----------------------------------------------------------------

Odour of two terpenes

Terpene Odour R-(-)-carvone spearmintS-(+)-carvone carawayR-(+)-limonene orangeS-(-)-limonene lemon--------------------------------------

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Ch. 1: Chemical Foundations · Chemistry: An Overview