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Chapter One The Air We Breathe What is in the air that we breathe? Can air be dangerous to our health? How can understanding chemistry help us decide?

The Composition of Our Air It’s a mixture – a physical combination of two or more substances present in variable amounts. 1.1

What’s in a Breath? Typical Composition of Inhaled and Exhaled Air Substance Inhaled air (%) Exhaled air (%) Nitrogen78.0 Oxygen Argon0.9 Carbon dioxide Water vaporvariable 1.1

Concentration Percent by mass Percent by volume Percent by number % by mass = mass of solute x 100% total mass % by volume = volume of solute x 100% total volume % by # = # of solute particles x 100% total # of particles 1.2

Concentration Parts per million (ppm) Parts per billion (ppb) ppm = # of solute particles million total particles ppb = # of solute particles billion total particles 1.2

Scientific Notation: A review = = 1.1 x x 10 – x 10 – = 1730 = 1.73 x x 10 –23 = 0.000,000,000,000,000,000,000, ,200,000,000,000,000,000,000 = x Note: same number of significant figures on both sides of each example.

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

The Bad Gases Carbon monoxide Ozone Sulfur oxides and nitrogen oxides Particulate matter, PM 1.2 We’ll take a closer look at each of these each in turn…

1.3 Toxicity – intrinsic health hazard of a substance. Air Pollutants: Risk Assessment Exposure concentration – Higher concentrations are more hazardous. Risk Assessment – evaluating scientific data and making predictions in an organized manner about the probabilities of an occurrence. Exposure time – at higher concentrations, exposure times must be shorter to minimize the hazard. Rate of respiration – at higher rates of breathing, more of the pollutant is taken into the body per minute.

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1.4 Average concentrations of air pollutants at selected locations in the U.S., in comparison with national ambient air quality standards.

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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50GoodGreen 51–100ModerateYellow 101–150 Unhealthy for sensitive groups Orange 151–200UnhealthyRed 201–300Very unhealthyPurple 301–500HazardousMaroon 1.4

Figure 1.9 Air Quality Index values for Phoenix 1.4 Variations reflect those in the local weather patterns. Regional events such as forest fires and volcanic eruptions can influence air quality.

AIRNOW Website for Local Air Quality Conditions and Forecasts

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Winter Haze in Paris: Looking down the Champs Elysees from the top of the Arc de Triomphe

Air Quality in Hawai’i Volcanoes National Park: Warning sign along crater trail

Air Quality in Hawai’i Volcanoes National Park: Halema’uma’u Crater (steam and sulfur dioxide emissions)

Air Quality in Hawai’i Volcanoes National Park: Sign at Park Ranger Station

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

Simplest form of matter: can't be broken down by chemical means Most elements are metals Shiny, malleable, ductile, good conductors of heat and electricity, most are solid at room temperature Non-metals Most gases at room temperature Solids are brittle not good conductors of heat or electricity Non-metals at upper right part of periodic table Metalloids Found along diagonal on PT separating metals and non-metals. Semiconductors (basis for computers, cell phones,...) base on metalloids Elements

Group Period The Periodic Table 1.6

Periodic Table Organized by properties Elements in a column usually have similar properties Rows called 'Periods' Columns called 'Groups' Group 1 – Alkali metals: most reactive metals Group 17 – Halogens: most reactive non-metals Group 18 – Noble Gases: almost never react

Atoms Smallest particle of an element ~ m in diameter There are about 5 x atoms in a single drop of water

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

Molecules Formed by bonding between two non metals Two or more atoms tied together by molecular (covalent) bonds Molecules have a fixed structure and arrangement of atoms. Some elements naturally exists as diatomic molecules: H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 –Hydrogen + “7” = seven diatomic elements

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

Chemical Formulas Shows composition, and sometimes structure, of a molecule Use chemical symbols from PT Subscripts on each symbol show how many of that atom are in the formula H 2 O, CO 2, CH 3 COOH, C 4 H 8

Naming Molecular Compounds For Binary compounds – made of only two elements: Name each element in order Change the ending of the second element to 'ide' Use prefixes to represent the subscripts from the formula 'Mono' is usually not used for first element

1. 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

2. Prefixes are used to designate the number of each type of element: Naming Binary Compounds of Nonmetals 1.8 N 2 O = dinitrogen monoxide (laughing gas) P 2 O 5 =diphosphorus pentoxide Notice the dropped “a” from “penta” – when both the prefix and suffix (in this case “oxide”) end and start, respectively, in a vowel, the vowel of the prefix is typically dropped; pentoxide rather than pentaoxide.

Chemical Reactions – Occur when compounds change into other compounds Reactants – compounds/elements that react – placed on left side of the equation Products – compounds/elements that are produced – placed on right side of the equation An arrow shows the direction of the reaction, left to right.

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

Chemical Equations Shows the reactants, products, and other information about the reaction: Phases – solid, liquid, gas reaction conditions – temperature, pressure catalysts The equation must be balanced to conserve mass – the initial and final mass must be the same

2 C + O 2 2 CO 1.9 Another look, pictorially – using space-filling models

Balancing Equations Write proper formulas – DO NOT CHANGE Place coefficients in front of each element or compound to balance one element at a time. Balance elements that occur in only two compounds first (often balance H and O last) Next balance elements that are in only one unknown (compounds without coefficients) Continue until all compounds are balanced Reduce coefficients to lowest whole #s Double check that all elements are balanced

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 (if any) 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

Complete combustion: fuel + oxygen → water + carbon dioxide CH 4 + 2O 2 → 2H 2 O + CO 2 Incomplete comb.: fuel + oxygen → water + carbon monoxide 2CH 4 + 2O 2 → 2H 2 O + 2CO Catalytic converters in automobiles catalyze the reaction to promote complete combustion and reduce CO emissions.

Hydrocarbons – All compounds that contain only hydrogen and carbon: Natural gas, Propane, many fossil fuels (gasoline has other additives to improve combustion) Organic Compounds – Compounds that contain at least one C-H bond Hydrocarbons are organic molecules Volatile organic compounds – VOCs VOCs include liquid fuels and industrial solvents. VOCs are pollutants and potential health threats to people and the environment.

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. One reason for removing tetraethyl lead from gasoline is that the lead gunked up or poisoned the catalysts in the converters. The other reason was to reduce the amount of lead in the air.

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1.13 Indoor Air Pollutants? Do you think of harmful pollutants when you light your incense candle or want to begin painting a room in the house? Why do you think these are considered indoor air pollutants?

Indoors and pollution: Staying indoors may protect against some pollutants: Ozone (O 3 ), SO x, and NO x are usually less than outside. Many pollutants may be trapped inside, though, so concentrations may be higher: Carbon monoxide and volatile organics (VOCs) may be the same or higher (from cleaning solvents, paint fumes, new textiles, incomplete combustion) Radon – seeps up from ground, or from some granite countertops, and is trapped indoors -Radon has been linked to lung cancer

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 1.14