Scientific & Chemical Fundamentals

Dr. Ron Rusay

Fall 2007

© Copyright 2003-2007 R.J. Rusay© Copyright 2003-2007 R.J. Rusay

Scientific & Chemical Fundamentals

Chemistry & the Scientific Method Matter : Classification & Properties Mathematics / Arithmetic:

Exponents, Significant Figures

Measurement & Units: (SI & metric) Conversions and Relationships:

Dimensional Analysis: Density, Percent VOCABULARY: Key Terms, Bold Style Learning

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© Copyright 1998-2007 R.J. Rusay

Textbook Reading

Chemical Foundations

1.1 Chemistry: An Overview1.2 The Scientific Method1.3 Units of Measurement1.4 Uncertainty in Measurement1.5 Significant Figures and Calculations1.6 Dimensional Analysis1.7 Temperature1.8 Density1.9 Classification of Matter

Science & The Science & The Scientific Method Scientific Method

Law vs. Theory

QUESTIONThe difference between a scientific law and a scientific theory can, at times, be confusing. For example, we will refer to the “Atomic theory” or perhaps the “Law of Gravity.” Should the Law of Gravity be changed to the Theory of Gravity?

1. Yes, no one can see gravity, it is better described as a theory.2. No, scientific laws are based on summaries of many

observations and gravity observations are well known andpredictable.

3. Yes, gravity is better described as a theory because gravity explains why masses attract each other and theories are about explaining observations.

4. No, keep it as a law, laws offer explanations and gravity explains why masses attract each other and laws are about explaining observations.

ANSWERChoice 2 follows the agreed-upon distinction between a theory and a law. Observations that consistently agree and provide the same result in a variety of systems become “Laws.” Theories are attempts to offer human interpretations and explanations about what was observed. Therefore, we should continue calling the summary about attractions the Law of Gravitation.

Section 1.2: The Scientific Method

Some Possible Steps in the Scientific Method

1.1. ObservationsObservations• qualitativequalitative• quantitativequantitative

2.2. Formulating hypothesesFormulating hypotheses• possible explanation(s) for the possible explanation(s) for the

observationobservation 3.3. Performing experimentsPerforming experiments

• gathering new informationgathering new information• testing whether the hypotheses are testing whether the hypotheses are

validvalid 4.4. Developing a theoryDeveloping a theory 5.5. Testing & RefiningTesting & Refining

Chemistry: The Study of Matter In all of its forms & all of its behaviors Sub-categories (not so distinct any longer)

• Organic: carbon• Inorganic: non-carbon• Organometallic: organic + inorganic• Analytical: what?, how much?, how pure?• Biological / Biochemistry: living organisms• Physical: energy, changes, rates• Nuclear: the nucleus• Environmental: interdisciplinary, eg. Oceanography

© Copyright 1998-2007 R.J. Rusay

Chemistry & Matter (Chemicals)

How many different chemicals do you think have been reported in the scientific literature?

A) 100,000B) 1,000,000C) 10,000,000D) 100,000,000E) 1,000,000,000

CAS Registry : ~12,000 in 1907; > 31 million June 2007CAS Registry : ~12,000 in 1907; > 31 million June 2007

Today ~ 500 new molecules are added / hrToday ~ 500 new molecules are added / hr

Chemistry & Matter (Chemicals)

How many different chemicals do you think have been reported in the scientific literature?

A) 100,000B) 1,000,000C) 10,000,000D) 100,000,000E) 1,000,000,000

CAS Registry : ~12,000 in 1907; > 31 million June 2007CAS Registry : ~12,000 in 1907; > 31 million June 2007

Today ~ 500 new molecules are added / hrToday ~ 500 new molecules are added / hr

Chemistry & Matter:Properties & States

• Physical vs. Chemical Properties

• Solid (s), Liquid (l), Gas (g)

• Homogeneous vs. Heterogeneous Mixtures

• Organization of atoms/molecules:

atoms/elements molecules/compounds

• Extensive vs. Intensive PropertiesVaries with amount (extensive) or does not vary

with amount (intensive)

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© Copyright 1998-2007 R.J. Rusay

Observations of Physical & Chemical Properties

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are needed to see this picture.

States of Matter

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are needed to see this picture.

Organization of Matter01_15

Heterogeneousmixtures

Physicalmethods Homogeneous

mixtures (solutions)

Atoms

Compounds Elements

Nucleus Electrons

Pure substances

Protons Neutrons

Quarks Quarks

Matter

Physicalmethods

Chemicalmethods

leptonsleptons

Up,down, strange, charm, bottom, topUp,down, strange, charm, bottom, top

Classification Classification of Matterof Matter

Organization of Matter01_15

Heterogeneousmixtures

Physicalmethods Homogeneous

mixtures (solutions)

Atoms

Compounds Elements

Nucleus Electrons

Pure substances

Protons Neutrons

Quarks Quarks

Matter

Physicalmethods

Chemicalmethods

leptonsleptons

up,down, strange, charm, bottom, topup,down, strange, charm, bottom, top

muons, tau, muons, tau, neutrinosneutrinos

Classification Classification of Matterof Matter

Using Physical & Chemical Properties: Distinguishing a Compound & a Mixture

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The effects of a The effects of a magnet on iron: filings magnet on iron: filings in a mixture and atoms in a mixture and atoms in a molecule. in a molecule.

Types of Mixtures

Mixtures have variable composition of two or Mixtures have variable composition of two or more components.more components.

AA homogeneous mixture homogeneous mixture is a solution (for is a solution (for example, vinegar: water + acetic acid, or steel & example, vinegar: water + acetic acid, or steel & bronze: solid metals)bronze: solid metals)

AA heterogeneous mixture heterogeneous mixture is, to the naked is, to the naked eye, clearly not uniform (for example, a bottle of eye, clearly not uniform (for example, a bottle of ranch dressing with two layers: water + oil, or two ranch dressing with two layers: water + oil, or two solids: iron and sulfur)solids: iron and sulfur)

Separating Mixtures• : Separates components of a mixture based upon differences in particle size. Examples: a precipitate from a solution, or particles from an air stream.

• Separation based upon differences in solubility of components in a mixture. Ideally the impurities are much more soluble in the solvent than the material being purified.

• Separation based upon differences in volatility (boiling points) of components in a homogeneous mixture. Example: ethanol & H2O

Filtration:

Crystallization:

Distillation:

Separating Mixtures

• Separation based upon differences in a compound’s solubility between two different solvents, typically immiscible liquids. Examples: ether & H2O, gasoline (hydrocarbons) and water.

• Separation based upon differences a compound’s solubility in a solvent versus a stationary phase. Examples: paper, thin layer (TLC), column, gas-liquid (GC); liquid-liquid: (HPLC), reverse phase.

Extraction:

Chromatography:

Filtration

Crystallization

Closer to an actual apparatus

Paper Chromatography

Thin Layer Chromatography

Stationary phase: silica or alumina

Procedure for Column Chromatography

Gas-Liquid ChromatographyGC at DVC

Element:Element: A substance that cannot be A substance that cannot be broken into simpler substances by broken into simpler substances by chemical means, eg. Fe, Iron or Schemical means, eg. Fe, Iron or S8 8 SulfurSulfur

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements only by broken down into elements only by chemical processes,eg. FeS, Iron chemical processes,eg. FeS, Iron (II) sulfide(II) sulfide

Elements & Compounds

QUESTIONIs a cup of coffee a homogeneous solution or a compound? Which of the following agrees with your reasoning?

1. The coffee in the cup is a homogeneous solution because it contains the same components throughout, but there are many compounds dissolved to make coffee.

2. The coffee in the cup is a compound because it has a setratio of components that make it the same throughout.

3. The coffee in the cup is both a compound and a solution.It looks the same throughout like a true solution, yet it alwayshas the same amount of each component.

4. The coffee in the cup is a heterogeneous solution not homogeneous because it contains distinct, differentcompounds dissolved to make coffee.

ANSWERChoice 1 provides the best reasoning. The coffee in the cup is a homogeneous mixture of components, making it a solution. The amount of each component can vary greatly from coffee bean to coffee bean. Compounds do not have a variable composition like solutions.

Section 1.9: Classification of Matter