Topics Covered Today:

Scientific Notation
Sources of Pollution
Atomic Structure

Chapter 1 The Air We Breathe (continued)

Scientific notation is a structured way of writing very large to very small numbers in a specific format that cuts down on error. For those students who may need a refresher or for the first time being introduced to the concept of scientific notation please refer to Appendix 2, page 467, of your book (Chemistry in Context 2/Text and Laboratory Manual: Applying Chemistry to Society). This type of notation if used correctly provides the student with an accurate way of interpreting and displaying data. For example: the number 21,000,000 is a large number with many commas and zeroes. There is always the chance that the reader of this number may read or recopy this number incorrectly, missing a comma or zero. In scientific notation the number 21,000,000 is 2.1x10⁷. As you can see there are fewer digits and no commas in the number expressed in scientific notation, therefore less of a chance in making mistakes in interpretation and writing.

Class Participation Examples of Scientific Notation:

21,000,000

Step #1: Assume that if there is no decimal that there is one at the very end of the number.: 21,000,000.

Step #2: Use the following formula.

Mantissa x 10 exponent

Mantissa = The decimal part of a common logarithm

The exponent is equal to the number of decimal places such that the last decimal lies behind the last single whole number. In this case the decimal will lie behind the "2" and one would have to count seven decimal places till one gets the decimal behind the "2". The exponent is seven or the power is to the 7th power (10⁷). The mantissa is equal to 2.1. There is no need to rewrite the zeroes since they are expressed by the power. Scientific notation of 21,000,000 is equal to 2.1x10⁷.

If the number to be expressed in scientific notation is greater than one then the exponent is positive (i.e. 10⁷), but if the number is less than one then the exponent is negative (i.e. 10^-7).

Other Examples:

781 = 7.81x10²

4,100 = 4.1x10³

.0046 = 4.6x10^-3

.000005 = 5.0x10^-6

.01 = 1.0x10^-2

Students will be expected to be able to translate regular numbers into scientific notation and vice versa.

Example: 7.8x10^-3 = 0.0078

In addition to converting numbers into scientific notation students will be expected to multiply, divide, add and subtract scientific numbers.

Rules of Division for Scientific Notation: 1.) Divide Mantissa numbers 2.) Subtract exponents

Example:

7.8x10^-3 = 3.9x10-3-(-1) = 3.9x10^-3 Rules of Multiplication for Scientific Notation:

1.) Multiply Mantissa numbers 2.) Add exponents

Example: (2.0x10³)(3.2x10^-20) = 6.4x10^-17

Rules of Addition for Scientific Notation:

1.) Add Mantissa numbers 2.) Keep same exponent (note -- numbers to be subtracted must have the same exponent)

Example:

4.0x10^-3 + 2.0x10^-2

*Cannot add numbers that do not have the same exponents

Convert:

4.0x10^-3 + 20x10^-3 = 24x10^-3

Rules of Subtraction for Scientific Notation:

1.) Subtract Mantissa numbers 2.) Keep same exponent (note: numbers to be added must have the same exponent)

Sources of Pollution

Questions Posed To The Class:

Where does pollution exist today? Which cities have the most pollution and what types of pollution do they have?

Pollution exists everywhere but the level of pollutants varies from place to place.

Los Angeles has one of the highest levels of nitrogen oxides in the United States. Los Angeles is also one of the most congested in cities in the United States in respect to the number of automobiles. One can make the inference that the high level of nitrogen oxides in Los Angeles can be attributed to its number of cars, or more specifically the exhaust pollution from all these cars.

Cities such as New York and Boston, which happen to be more industry oriented than other cities in the United States, have been found to have higher levels of sulfur dioxides. An important question to ask is where does sulfur dioxide originate from in industrial cities? Manufacturing plants use coal as their source of energy. Coal is used to generate a majority of the electricity we use in everyday living. About 8% to 11% of the energy we use is generated by nuclear power plants and that is on the decline due to a lack in technology of proper disposal of radioactive waste. An even smaller percentage of electrical power comes from hydroelectric technology.

The United States has vast resources of coal. Not all of the stockpiles of coal are necessarily of the highest grade, meaning that the coal contains impurities such as sulfur. Coal itself is composed of carbon and oxygen and degraded/combusted into carbon dioxide. Coal can contain 1-4% sulfur. When coal is burned sulfur dioxide (SOX) is produced. The letter X, as in many mathematical equations, stands for a number. This number is equal to the number of oxygen molecules bond to sulfur.

Coal is combusted to form SO₂, SO₃, and/or H₂SO₄ (a component of acid rain). More oxygen atoms can be attached to sulfur at the top of the combustion stack of an industrial/manufacturing plant due to a higher concentration of oxygen coming from the atmosphere rather than the bottom of the stack.

Production of SO₂ in the stack:

S + O₂ (SO₂)

At the top of the stack:

SO₂ + O₂ ( SO₃)

Balance:

4SO₂ + 2O₂ = 4SO₃

Reduce:

2SO₂ + O₂ ( 2SO₃)

This is typically a slow reaction and wind helps push the sulfur oxide away from the stack but ash, a byproduct of the combustion of coal, acts as a catalyst. SO₃ collects at the top of the stack and the reaction of water and sulfur trioxides is speeded up by ash to create sulfuric acid, a.k.a. acid rain.

SO₃ + H₂0(atmosphere) = H₂SO₄ (exists as an aerosol of fine suspended droplets of water; Wind pushes the acid rain across borders.)

In the United States, most of the acid rain is produced in the midwestern states (i.e. Ohio) that rely heavily on manufacturing as a major source of capital. In fact, many regions of the world in which a lot of acid rain precipitation occurs are not responsible for this pollution but receive it from clouds containing sulfuric acid as they are pushed along jet streams. It is also important to note that many countries do not place the same restrictions the U.S. has imposed on sulfur oxide production from its industries. Regulation is often outweighed by political agendas for a stronger economy in those countries.

In the 1980’s and 1990’s, with the help of social outcries and the Clean Air Act, there have been low tech and high tech adjustments made to try deal with the problem of sulfur dioxides in the environment caused by the manufacturing and power industries.

Low tech: Using a higher grade of coal.
Low tech: Higher smoke stacks which enable winds to disperse of the sulfur oxides more efficiently than at lower altitudes.
High tech: Putting ‘scrubbers’ on stacks which prevent ash as acting as a catalyst.

Another Type of Pollution: Nitrogen Oxides

Automobiles are the main culprits in the production of nitrogen oxides or NOX. The exhaust coming from automobiles is a combination of water, carbon dioxide, and incompletely burned organic molecules (i.e. carbon monoxide). States today regulate the concentration of gases that are emitted from your car’s tailpipe. Most often cars will be emission tested annually or biannually for the percentage of carbon monoxide and carbon dioxide that are in the cars exhaust fumes. The advent of the catalytic converter was crucial in bringing down the levels of carbon monoxide in the atmosphere over the last decade or so.

Catalytic converter reaction: CO (a combustion product) + O₂ = CO₂ + H₂O How then do cars produce nitrogen oxides if nothing in the fuel contains nitrogen? The nitrogen is coming simply from the air we breathe.

N₂ (air) + O₂ + Heat (engine) + 2NO

Cars of today are run hotter than in the past, which is a problem because it speeds up the reaction that creates nitrogen oxides.

Cars also produce ozone. At ground level ozone is a hazardous pollutant. We want it in the stratosphere where it can aid in blocking harmful radiation.

*Students will be held responsible for reading the section in the book pertaining to "Risk Assessment".

Photochemical Smog

Photochemical smog is termed ‘photochemical’ because it requires sunlight to cause the chemical reaction that creates smog.

In your book on page 23 there is a picture of smog in downtown Los Angeles. It is a brown haze that blankets cities and is strongest when the sun is at its peak, usually around 2:00-3:00pm. As the day goes on the more smog can be seen with the belief that more cars are out on the streets providing the gaseous pollution (NOXs) that make up smog.

Cars ( Nitrogen Oxides + Volatile Organic Components (VOCs) + Energetic Push from Ultraviolet Light ( Brown Haze, a.k.a. Smog)

VOCs = little inorganic molecules not completely burned in combustion by the engine

Smog affects certain people differently. To a certain degree the healthy, young adult to middle-aged person can deal with daily smog. Children, asthma and emphysema patients, and the elderly undertake serious health risks when smog is around. Smog is an irritant to the lungs and many of the long-term affects are still undetermined.

*Remember that the test will comprised of problems contributed by homework problems, material assigned to be read, and your lecture notes.

Chapter 2 Protecting the Ozone Layer

The molecular formula for ozone is O₃. The molecular formula for the oxygen we breathe is O₂. With the molecular formulas for ozone and oxygen almost being the same what is the difference between the two? Ozone and oxygen are allotropes of each other.

Allotropes are different molecular forms of the same element. In order to address the previously posed question we must have a basic understanding of bonding.

Although there are 26 known parts to the atom we are only interested in 3 of them: Protons, Neutrons, and Electrons.

A table constructed in class:

PARTICLE	MASS	CHARGE	LOCATION
Proton	1 amu	p +	Nucleus
Neutron	1 amu	0	Nucleus
Electron	1/1838 amu	e -	Outer shell(s)

Chapter 2 will be continued next class

Safety Lab Movie: Key Highlights

Starting with safety:
You will be introduced to new and sometimes dangerous techniques so let’s be careful.

1.) Know the rules and techniques well in advance before entering the lab.
2.) Handle chemicals safely. Use small controllable containers.
3.) Mix chemicals only when advised by instructor.
4.) Read and reread instructions.
5.) Know our chemicals.
6.) Add acids to a container of water via a rod.

Contaminants:

1.) Hold your stoppers. Do not let them touch contaminated surfaces.
2.) Keep chemicals away from your face.
3.) Do not touch or directly smell chemicals.
4.) Smell chemicals at an arm’s length away and fan the odor towards you.
5.) Set bottles and containers containing chemicals out of your way if not directly using them.
6.) Know which chemicals need to be opened in the fume hood.
7.) Work only with clean glassware.
8.) Pour out of reagent bottles and not into them to prevent contamination.
9.) Pour waste in specific containers designated for waste.
10.) No mouth-pipetting.

Spills:

1.) Report spills immediately to your instructor.
2.) Allow your teacher to assess the cleanup procedures.
3.) Use absorbent material when necessary. Then sweep up absorbent.
4.) The material that is spilled should have its own waste container.
5.) Do not pour chemicals down the drain unless told to do so.
6.) Clean your hands after the spill has been contained and disposed.

Bunsen Burners:

1.) Gas comes from an outlet.
2.) There is a hose that distributes the gas to the Bunsen burner.
3.) Check the hose to make sure that there are no holes or cracks.
4.) Hose must be snug at the outlet of the gas and at the inlet of gas on the burner.
5.) There is a valve at the bottom of the burner that controls the amount of gas flowing.
6.) Light the Bunsen burner with a starter or match. Strike near the side of the top of the burner but never directly in the path of where the flame would occur.
7.) A blue flame is the hottest flame possible (there should be a lighter blue inner cone and at this tip is where the hottest temperature is reached).
8.) If at any point you smell gas you should immediately turn off the gas source.
9.) Cracks in glassware are lethal.
10.) Water baths are useful for heating test tubes evenly and safely.
11.) Only heat containers with openings.
12.) Heated glassware needs to be handled with gloves and tongs.
13.) Heat volatiles in a water bath and never directly over a flame.

Thermometer Safety:

1.) Don’t Break Them! If you do alert your instructor and those around you immediately.

Glass Tubing Safety:

1.) Don’t Cut Yourself! Handle all glassware delicately.

Clothing:

1.) Must be sturdy.
2.) Preferably not flammable.
3.) Clothes should not be loose. Snug yet not constricting movement.
4.) Use a chemical apron.
5.) No open-toed footwear.
6.) Hair needs to be tied up.
7.) Remove rings and watches.
8.) Only long pants and skirts.
9.) Goggles at all times.
10.) No contact lenses if possible.

Behavior In Lab:

1.) No fooling around. 2.) Keep personal belongings out of the lab.
3.) No putting on of cosmetics in the lab.
4.) No food in the lab.

Emergency Equipment: 1.) Locate where the eyewash, fire blanket, fire extinguishers, shower and exits are in the lab.

Last piece of business: Starting on page 111 of your book read the experiment for Friday’s lab: Preparation and Properties of Gasses in a Breath.

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