Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A Project of the American Chemical Society PowerPoint slide presentation by Carl E. Heltzel, Transylvania University

Chapter One The Air We Breathe

The Composition of Our Air It’s a mixture – a physical combination of two or more substances present in variable amounts 1.2

What’s in a Breath? Typical Composition of Inhaled and Exhaled Air SubstanceInhaled air (%) Exhaled air (%) Nitrogen Oxygen Argon0.9 Carbon dioxide Water

Concentration Terms Parts per hundred (percent) Parts per million (ppm) Parts per billion (ppb) Atmosphere is 21% oxygen = 21 oxygen molecules per 100 molecules of air Midday ozone levels reach about 0.4 ppm = 0.4 ozone molecules 1 x 10 6 molecules of air Sulfur dioxide in the air should not exceed 30 ppb = 30 sulfur dioxide molecules 1 x 10 9 molecules of air 1.2

21% means 21 parts per hundred means 210 parts per thousand means 2,100 parts per ten thousand means 21,000 parts per hundred thousand means 210,000 parts per million The difference between pph and ppm is a factor of 10,000 Try Chapter 1 Figures Alive! for practice 1.2

EPA’s Air Quality Index Air Quality Index (AQI) Values Levels of Health Concern Colors When the AQI is in this range:...air quality conditions are:...as symbolized by this color: 0  50 GoodGreen 51 – 100ModerateYellow 101 – 150Unhealthy for sensitive groups Orange 151 – 200UnhealthyRed 201 – 300Very unhealthyPurple 301 – 500HazardousMaroon 1.3

YearGood (0–50) Moderate (51–100) Unhealthy for Sensitive Groups (101–150) Unhealthy (>150) Table 1.4 Air Quality Index values for Houston 1.3

1.4 Toxicity – intrinsic health hazard of a substance Air Pollutants: Risk Assessment Exposure – the amount of the substance encountered

1.4 Characteristics of Risk Perception Exposurevoluntaryinvoluntary Effectimmediatedelayed Alternativesnonemany Knowledge of consequenceknownunknown Occupational encounteredyesno Image of hazardcommondread Severity of consequencereversible irreversible Controllableyesno AcceptableUnacceptable

The Regions of the Lower Atmosphere Atmospheric pressure changes with altitude 1.5

Classifying Matter All Matter Pure Substances Mixtures Can it be separated by a physical process? CompoundsElements YES NO Can it be broken down into simpler ones by chemical means? NOYES 1.6

Classifying Matter Classify each of these as an element, a compound, or a mixture: carbon dioxide nickel cocaine water compound element compound fluorine table salt soap sea water element compound mixture 1.6

Group Period The Periodic Table

A space filling model for a water molecule, H 2 O Oxygen atom Two hydrogen atoms A molecule is a combination of a fixed number of atoms held together in a certain spatial arrangement. The chemical formula symbolically represents the type and number of each element present. 1.7

Many nonmetals occur as diatomic (made up of two atoms) molecules H2H2 N2N2 O2O2 Cl 2 1.7

Naming Binary Compounds 1. Name the more metallic element first, followed by the name of the less metallic element, modified with the suffix “ide” KBr postassium bromide BeO beryllium oxide ZnS zinc sulfide 1.8

2. Prefixes are used to designate the number of each type of element: Naming Binary Compounds number of atomsprefix 1mono 2di 3tri 4tetra 5penta 6hexa 7hepta 8octa 9nona 10deca 1.8

Chemical reactions are characterized by the rearrangement of atoms when reactants are transformed into products C + O 2 CO reactants product But the number of atoms on each side of the arrow must be equal (Law of Conservation of Mass) 2 C + O 2 2 CO (balanced) 2 carbon atomstwo carbon atoms 2 oxygen atomstwo oxygen atoms This is an example of a combustion reaction 1.9

+ 2 C + O 2 2 CO 2 1.9

Balancing equations: -if an element is present in just one compound on each side, balance it first -balance anything that exists as a free element last - balance polyatomic ions as a unit - check when done – same number of atoms, and same total charge on both sides C 3 H 8 + O 2 CO 2 + H 2 O C 3 H O 2 3 CO H 2 O 3 C atoms 8 H atoms 10 O atoms 3 C atoms 8 H atoms 10 O atoms 1.9

Coal + O 2 SO 2 (1-3% sulfur) SO 2 + O 2 2 SO 3 Direct Source of Sulfur Trioxide Good News: Since 1985 we have seen a 25% reduction in SO 2 emissions in the U.S.

1.11 Direct Source of Nitrogen Oxides N 2 + O 2 + high temp 2 NO (nitrogen oxide) High temperatures from auto engine or coal-fired power plant NO is very reactive: 2 NO + O 2 2 NO 2 Simplified version of chemistry that occurs

1.11 Catalytic converters are used to catalyze the conversion of CO to CO 2 The converters also reduce the amount of Volatile Organic Compounds (VOCs) from tailpipe exhaust

1.12 Formation of Tropospheric Ozone NO 2 NO + O O + O 2 O 3 sunlight O 3 is not directly emitted, it is a secondary pollutant- produced from other pollutants Discuss the relationship between hydrocarbon and ozone concentrations in the atmosphere

Ozone (O 3 ) If one breath of air contains 2 x molecules and atoms, and the acceptable ozone level is 0.12 ppm, how many molecules of O 3 are in each breath? 2 x molecules and atoms in a breath of air x 0.12 O 3 molecules 1 x 10 6 molecules and atoms in air = 2 x O 3 molecules in a breath How many oxygen atoms are in each breath? 2 x O 3 molecules x 3 O atoms___ 1 O 3 molecules = 6 x O atoms 1.12

1.14 Indoor Air Pollutants?