chemical basics 1 - university of sussex · physical universe chemistry 120 the scientific method:...

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Chemistry 120

Chemistry 120Dr. J. F. C. Turner

409 Buehler Hall

Office 4-8591

Lab 4-9316

email [email protected]

Chemistry 120

• Lecture: 80%

• 6 Quizzes 25%

• 3 Examinations 25%

• Final 30%

• Lab: 20%

Chemistry 120

• Grade Cutoffs ‘

A 100 – 80 C+ 68 – 69.9

B+ 78 – 79.9 C 60 – 67.9

B 70 – 77.9 D 50 – 59.9

F 0 – 49.5

There is no curve

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Chemistry 120

1. Matter, Measurement and the Scientific Method (Ch. 1)

2. Atoms, Molecules and Ions (Ch. 2)

3. Stoichiometry (Ch. 3)

4. Chemical reactions in Aqueous solution (Ch. 4)

5. Gases (Ch. 5)

6. Thermochemistry (Ch. 6)

7. Atomic Structure (Ch. 7)

8. Atoms, Electrons and the Periodic Table (Ch. 8)

9. Chemical Bonds (Ch. 9)

10. Molecular Structure (Ch. 10)

11. States of Matter and Intermolecular Forces (Ch. 11)

Chemistry 120

“People have now-a-days,” he said, “got a strange opinion that everything should be taught by lectures. Now I cannot see that lectures can do so much good as reading the books from which the lectures are taken. I know nothing that can be best taught by lectures, except where experiments are to be shown. You may teach chemistry by lectures. – You might teach making of shoes by lectures”.

Samuel Johnson to Boswell, 1766, A Guide to Old English 1991

Chemistry 120

Chemistry is an ancient science, with many hundreds of years of history.

Chymistry, an art whereby sensible bodies contained in vessels........are so changed, by means of certain instruments, and principally fire, that their several powers and virtues are thereby discovered, with a view to philosophy or medicine.

Samuel Johnson, A Dictionary of the English language 1755

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Chemistry 120

Chymistry, an art whereby sensible bodies contained in vessels..are so changed, by means of certain instruments, and principally fire, that their several powers and virtues are thereby discovered, with a view to philosophy or medicine.

Dr. Samuel Johnson, (1709–1784)literary titan of the 18th century, essayist,lexicographer, poet,editor, critic, second most quoted person in the English language, after Shakespeare

Chemistry 120

The etymology of chemistry is based on the word alchemy, which, in turn, is based on the Greek ? ? ??? or ?????? , found in the Decree of Diocletian against ‘the old writings of the Egyptians, which treat of the ? ? ???(transmutation) of gold and silver’.

Chemistry 120

‘....the old writings of the Egyptians, which treat of the ?????? (transmutation) of gold and silver....’Gaius Aurelius Valerius Diocletianus(240? – 311)

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Chemistry 120

Chemistry 120

Experimentz of alkamye ·Þe poeple to deceyue.

William Langland (1332? – 1400?)

The vision of William concerning Piers Plowman. 1377

Les Très Riches Heures du Duc de BerryMarch Folio 3v

Chemistry 120

A modern definition of chemistry.....

That branch of physical science and research, which deals with the several elementary substances, or forms of matter, of which all bodies are composed, the laws that regulate the combination of these elements in the formation of compound bodies, and the various phenomena that accompany their exposure to diverse physical conditions.

Oxford English Dictionary http://dictionary. oed.com/

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Chemistry 120

Chemistry is concerned with the structure and properties of matter as well as the interchange of matter by reaction.

It differs from the other natural sciences or physical sciences as it is

CREATIVE

and thus has elements of art and is a sciencenonetheless.

Chemistry 120

We ask the question:

What is matter?

- if we are to understand chemistry, we need to know what we mean by matter.

Chemistry 120

What is matter?

Matter is the material of which the physical world is composed – the fabric of the universe.

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Chemistry 120

The Fabric of the Universe?

Chemistry 120

Some forms of matter I

Matter comes in many different forms........

Chemistry 120

Some forms of matter II

Matter comes in many different forms........

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Chemistry 120

? Defects on the surface of copper metal

Impurities in the surface of copper metal ?

Some forms of matter III

Chemistry 120

The Scientific Method

The Scientific Method is a way of thinking about the physical world which allows us to:

1 Rationalize what we observe

2 Predict what we may observe

3 Understand the underlying principles of the physical universe

Chemistry 120

The Scientific Method: Knowledge of the World

Knowledge comes in two forms

– ‘interior’ and ‘exterior’Interior: Fred and Jane are in love.

If we take any Fred, is this Fred in love with Jane?

Exterior: The mass of a mole of iron atoms is 55.845 (2) gmol-1

If we take 1 mole of iron, it always has a mass of 55.845 (2) gmol-1

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Chemistry 120

The Scientific Method: Knowledge of the World

Interior Knowledge comprises

revealed truths

- such truths are dependent on the person(s) involved.

Exterior Knowledge comprises

empirical or experimental truths

- such truths are measurable and are independent of person.

Chemistry 120

The Scientific Method: Natural Laws

We can define a Natural Law as the sum of human ‘exterior’ observations.

- All human observations fit with the natural law else it cease to be a law – some thing is missing and the natural law is not universal.

- Logic is not sufficient to explain Science as Science is based in Human Experience

Chemistry 120

The Scientific Method: Logic and the problem of ravens

We can state that

“All ravens are black”

which is equivalent to

“All non-ravens are non-black”

However, observation of e.g. a red car does not demonstrate the color of ravens

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Chemistry 120

Structure Of The Scientific Method:

Hypothesis – an abstract model of the system in question

Experiment – the test of the hypothesis by careful procedures that control the variables in the hypothesis that generate data

Interpretation and Modification

Chemistry 120

Structure Of The Scientific Method:

Hypothesis

Experiment

DataInterpretation

Modification of hypothesis

Chemistry 120

The Scientific Method: Scientific Knowledge

Scientific Knowledge is:

1. Reproducible

2. Testable

3. Predictive

4. Tentative

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Chemistry 120

The Scientific Method: Natural Laws

We can define a Natural Law as the sum of human ‘exterior’ observations.

- All human observations fit with the natural law else it cease to be a law – some thing is missing and the natural law is not universal.

Chemistry 120

The Scientific Method: Reproducibility

If the structure and dynamics of the Universe can be explained by a non-random set of ‘Natural Laws’, then independent measurements of the same system MUST reproduce the same result.

Chemistry 120

The Scientific Method: Testability

As a ‘Natural Law’ is the sum of human experience of a system, then we must be able to test the system and derive ‘experience’ of the system.

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Chemistry 120

The Scientific Method: Predictive

If the hypothesis about the system is correct, it must be able to predict properties of that system that we can measure.

Chemistry 120Chemistry 120Matter, Measurement and the Scientific Method

The Scientific Method: Uncertainty

All ‘Natural Laws’ are uncertain and are subject to change when human experience runs contrary to these laws.

Relativity Newton’s Laws of Motion

Quantum Mechanics Newtonian Gravitation

Chemistry 120

Conservation of Mass and Energy

One of the most basic Natural Laws

Matter and Energy are neither created or destroyed

Chemical transformations, by reaction or through physical means, always conserve mass

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Chemistry 120

Two Chemical processes...

? one fast,

one slow ?

.......that both conserve

mass and energy.

Chemistry 120

Classification of Matter

Matter can be divided into two classes

– solids

– fluids

- gases

- liquids

Chemistry 120

Solids

• Rigid – they have shape

• Incompressible

• Have a definite volume

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Chemistry 120Fluids

• Have no shape

• Liquids are incompressible

• Gases are compressible

• A liquid has a volume but a gas has the volume of the container.

Chemistry 120

Chemical Composition of the World: Atoms 101

???? “indivisible, uncuttable”All matter is composed of atoms which cannot be further split into smaller portionsAtoms are completely solidAtoms are homogeneous, with no internal structureBetween atoms there is empty spaceAtoms differ in size

Democritus (c.460 -c.370 B.C.)

Chemistry 120

John Dalton (1766 -1844)

Chemical Composition of the World: Atoms 200

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Chemistry 120

Chemical Composition of the World: Atoms 300Thomson’s“blueberry muffin” modelElectrons embedded in a shell of positive charge

Rutherford’s modelElectrons randomly circulating around nucleus made of protons

Chemistry 120

The Chemical Composition of the World

There are 112 distinct chemical building blocks or ELEMENTS which make up all known matter

• An element cannot be transformed into any other element by chemical means or by ‘conventional’ physical processes

• Elements can be combined to produce ‘compound bodies’ - compounds

Chemical Basics

Chemistry 120Chemical Basics

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Chemistry 120

Chemical elements are abbreviated with a symbol, usually but not always abbreviated to their name:

Calcium Ca Radon Rn

Barium Ba Magnesium Mg

Chlorine Cl Oxygen O

Chemical Basics

Chemistry 120

Elements, whose symbols are not always abbreviated to their name:

Sodium Na (Latin Natria)

Potassium K (Latin Kalia)

Silver Ag (Latin Argentum)Gold Au (Latin Aurum)

Mercury Hg (Latin Hydrargyrum)Tungsten W (from the mineral Wolframite)

Chemical Basics

Chemistry 120

Elements are combined into compounds, where the number of atoms in the compound is shown by a subscript

FeCl3 C6H12O6 H2O CO2

Physical processes

Melting, boiling, crushing, evaporating, freezing

do not change compounds or elements

Chemical Basics

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Chemistry 120

Chemical processes convert

Elements into compounds

Compounds into elements

Compounds into compounds

Chemical Basics

Chemistry 120

Elements and compounds are termed

Substances

which we can define as

A species of matter which is homogenous and with a definite chemical composition

Chemical Basics

Chemistry 120

Substances (elements or compounds) can form

Mixtureswhich are either

heterogenous- different in different places in

the sampleor

homogenous- the same everywhere in the

sample

Chemical Basics

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An example of a heterogenous mixture is granite

- it appears to be one material but........


...it is composed of a mixture of minerals in varying proportion, where each point in the piece is not necessarily the same.


An example of a homogenous mixture is airwhich is composed of

Gas Mole percent Boiling point

Nitrogen (N2) 78.084 -195.79 °C

Oxygen (O2) 20.947 -182.9 °C

Argon (Ar) 0.934 -185.8 °C

An example of a homogenous mixture is airwhich is composed of

Air can be cooled to remove the oxygen and thus separate the mixture

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Chemistry 120

Elements

Compounds

Heterogenous

MixtureHomogenous

Mixture

Substances

Physical changes

Chemical changes

Chemical Basics


Scientific Measurement and Notation

Imagine we measure the mass of a ball bearing a number of times and we find that the mass is

1 4.76g 2 4.74g 3 4.75g

4 4.74g 5 4.75g 6 4.76g

The average mass is the sum of the masses divided by the number of measurements:

Chemistry 120


Average mass = 4.76+4.74+4.75+4.74+4.75+ 4.766

Chemical Basics

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Average mass = 28.56



Average mass = 4.75g




but we know that there is uncertainty in the measurement in the last figure – it varies between 0.04 and 0.06.

So we say that there are two figures that are certain and one in which there is a small uncertainty and we say that there are

3 Significant figures

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but we know that there is uncertainty in the measurement in the last figure – it varies between 0.04 and 0.06.

So we say that there are two figures that are certain and one in which there is a small uncertainty and we say that there are

3 Significant figures



The Rules for Significant figures

1. All non-zero figures are significant

2. All zeros to the left of a non-zero figure are not significant e.g. 0.00593

3. All zeros between non-zero figures are significant e.g. 7.098532

4. All zeros to the right of non-zero digits are significant



In a multiplication or division calculation:

Give the answer only to the number of significant figures that occur in the measurement that has the smallest number of significant figures.

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Density = ? = m/V

When m = 123g and V = 66ml,

? = m/V = 123/66 = 1.86363636364gml-1

? = 1.87gml-1

? = 1.9gml-1

2 significant figures

Round up



In a addition or subtraction calculation:

Give the answer only to the number of significant figures that occur in the measurement that has the smallest number of decimal places.



17.421g + 1.92g =

1420ml + 0.1223ml =

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17.421g + 1.92g = 19.341g

= 19.34g

1420ml + 0.1223ml = 1420.1223ml

= 1420ml


Scientific Units

In science, we use SI (Systeme Internationale) exclusively.

For chemists, the most important areLength meter mMass kilogram kgTime second sTemperature kelvin K (not oK!!)Amount of substance mole mol

Chemistry 120

Units are important.......Mars Climate Orbiter (MCO) was launched in late 1998, followed by Mars Polar Lander (MPL) and Deep Space 2 launched in early 1999. MCO failed to achieve Mars orbit because of a navigation error, resulting in the spacecraft entering the Mars atmosphere instead of going into the planned orbit. ............. Spacecraft operating data needed for navigation were provided to the JPL navigation team by prime contractor Lockheed Martin in English units rather than the specified metric units. This was the direct cause of the failure.

Chemical Basics

~ $250m

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Scientific Units

In science, we use SI (Systeme Internationale) exclusively.

For chemists, the most important areLength meter mMass kilogram kgTime second sTemperature kelvin K (not oK!!)Amount of substance mole mol


Scientific Units

Large or small fractions of the basic units, (m, kg, s, K) are written in scientific notation with the order of magnitude shown by a power of ten.

1200 m = 1.2 x 103 m

0.0012 m = 1.2 x 10-3 m

0.00000000012 g = 1.2 x 10-10g


67,000,000 s =

0.00005 K =

34 m =

4,500,000,000,000,000,000,000 m =

5,768,000 s =

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67,000,000 s = 6.7 x 108 s

0.00005 K = 5 x 10-5 K

34 m = 3.4 x 101 m

4,500,000,000,000,000,000,000 m = 4.5 x 1021 m

5,768,000 s = 5.678 x 106 s


Scientific Units

We denote the powers of ten by a prefix to the unit symbol.

The common ones are

103 kilo km 10-2 centi cm

106 mega MJ 10-3 milli mm

109 giga Gpa 10-6 micro ?m

10-9 nano ns


Length defines the spatial extent of a body in one dimension.

The formal definition is

"The metre is defined as the length of the pathtravelled by light in vacuum during a time interval of 1/299 792 458 of a second"

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Area defines the spatial extent of a body in two dimensions

L1

L2

A = L1 x L2

Unit of area is a derived unit – it is combination of other units. In this case they are the same – the square meter, m2.

Units are still OK for

circular areas: A = 4?r2


Volume defines the spatial extent of a body in three dimensions

Unit of volume is a derived unit – it is combination of other units. In this case they are the same – the cubic meter, m3.

L1

L2

L3

V = L1 x L2 x L3

Units are still OK for

spherical volumes: V = 4/3?r3


Area conversions

1 cm = 1 x 10-2 m

1 cm2 = (1 x10-2 m)2 = (1 x 1 x 10-2 x 10-2)m2

= 1 x 10-4 m2

1 cm

1 cm 1 cm2

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Volume

1 cm = 1 x 10-2 m

1 cm3 =


Volume

1 cm = 1 x 10-2 m

1 cm3 = (1 x 10-2 m)3

=


Volume

1 cm = 1 x 10-2 m

1 cm3 = (1 x 10-2 m)3

= (1 x 1 x 1 x 10-2 x 10-2 x 10-2 ) m3

=

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Volume

1 cm = 1 x 10-2 m

1 cm3 = (1 x 10-2 m)3

= (1 x 1 x 1 x 10-2 x 10-2 x 10-2 ) m3

= 1 x 10-6 m3


So if I know that 1 cm3 = 1 x 10-6 m3, 3.4 cm3 can be found in m3 by

1 cm3 = 1 x 10-6 m3



3.4 x 1 cm3 = 3.4 x 1 x 10-6 m3

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3.4 x 1 cm3 = 3.4 x 1 x 10-6 m3

3.4 cm3 = 3.4 x 10-6 m3


So if I know that 1 cm2 = 1 x 10-4 m2, 78 cm2 can be found in m2 by

1 cm2 = 1 x 10-4 m2



78 x 1 cm2 = 78 x 1 x 10-4 m2

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78 x 1 cm2 = 78 x 1 x 10-4 m2

78 cm2 = 78 x 10-4 m2



78 x 1 cm2 = 78 x 1 x 10-4 m2

78 cm2 = 78 x 10-4 m2

BUT 78 x 10-4 m2 = 7.8 x 101 x 10-4 m2



78 x 1 cm2 = 78 x 1 x 10-4 m2

78 cm2 = 78 x 10-4 m2

BUT 78 x 10-4 m2 = 7.8 x 101 x 10-4 m2

SO 78 x 10-4 m2 = 7.8 x 10-3 m2

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Chemistry 120

Distance to the Horizon 1026 m

Distance to M31 1022 m

Distance to the center of the galaxy 1020 m

Distance to the Nearest Star 1017 m

Distance of Earth to Sun 1011 m

Radius of Sun 108 m

Radius of Earth 106 m

Chemical Basics

Chemistry 120

Radius of Knoxville TN 104 m

A small cow 100 m

Unraveled human DNA strand 10-3 m

Typical size of dust 10-4 m

Typical size of a cell 10 -6 m

(1 micron, 1?m)

Chemical Basics

Chemistry 120Chemical BasicsThe Planck Length 10-35 m

Radius of the proton: 10-18 m

Radius of Electron "orbit"

about an atomic nucleus 10-15 m

Wavelength of 1 MeV gamma-ray : 10-12 m

Spacing of atoms in solid copper : 10-10 m

(1 Ångstrom, 1Å)

?

chemical basics 1 - university of sussex · physical universe chemistry 120 the scientific method:...

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