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Kenneth Kang
Monday, December 16, 1996
Course in Progress Draft

Chemistry


Chemistry

"Chemistry is the study of the compostion of substances and the changes that substances undergo." The fields include:

The Scientific Method

"The scientific method incorporates observations, hypotheses, experiments, theories and laws." People make observations when they spot a pattern. Hypotheses then try to explain what is going on. The experiment and produce relavent data. This allows the affirmation or refutation and later reformulation of the hypothesis which after extensive testing becomes a theory. The difference between this and a law is that a law decribes nature, not explains it.

Chemistry developed from alchemy where people tried to change cheap metals to gold. This explored chemical properties.

Properties of Matter

Matter is stuff which occupies space and has stuff. "A substance is a particular kind of matter that has a uniform and definate composition." All matter possess unchangable qualities which are called physical properties. These characteristics can be observed without changing the substance itself.

The States of Matter


Property            SolidSolid           LiquidLiquid         GasGas or vapor      

Mass                Definite             Definite             Definite             

Shape               Rigid                Indefinite           Indefinite           

Volume              Definite             Definite             Indefinite           

Response to         Very small           Moderate expansion   Large expansion      
Temperature         expansion                                                      
Increase                                                                           

Compressibility     Almost               Almost               Compressible         
                    incompressible       incompressible                            



Table 1

Physical Changes

"A physical change will alter a substance without changing its composiotn." This is like changes of state.

Mixtures

Mixtures blend two plus substances either uniformly, homogeneously, or non-uniformly, herterogeneously. A type of homogeneous mixture is a solution, a thing dissolved in a fluid. A part of it is called a phase. To separate a solution, one distills it and vaporizes the liquid.

Elements and Compounds

Elements are the simplest forms of matter that exist in laboratories and retain the chemical properties. Combining them forms compounds with different properties.

Chemical Symbols

The chemical symbols are written with a capital letter and if necessary, lowercase letters. They can describe compounds and the ratio of elements in the compound.

Energy

There are many kinds of energy, but each is capable of doing work. Some of it has the potential energy can do stuff. Kinetic energy is already in movement. There is also energy in the form of heat which is the transfer of energy between areas of different temperature.

Conservation of Energy

Energy is converted between forms. It is lost along the way, but it is conserved and cannot be destroyed or created. This is called the law of conservation of energy.

Chemical Reactions

Chemical reactions change one or more substances into another substance(s). The stuff that you start with are called reactants and the stuff that comes out is called the product. Energy is often needed or released in these reactions. In some chemical changes a change of state occurs, specifically, if solids separate from a liquid, the solid is called a precipitate. Each substance has chemical properties which dictate how it acts with other substances.

Conservation of Mass

"Any physical or chemical reaction, mass is neither created nor destroyed," quoteth the law of conservation of mass.

Lecture 9-3-96: Big Bang

Chemistry generally studies on matter, or material, and its changes. This study can occur anywhere, including air, water, and test tubes. The formation of the matter has generally be created from the Big Bang.

This is the start of the universe from a small, dense ball which was a mass of energy at 1014 K that encompassed the whole universe. This explodes and goes to a solar system in 1 second. Quarks and electrons form in a millisecond. Within the second, protons and neutrons form. A minute to eight minutes passes and helium nuclei form creating masses of energy.

After 300,000 years, atoms form and light can pass through the universe. Electrons are resposible for interacting with light. When they are orbiting, they allow photons to travel through. It is unclear what happend between this time and the formation of galaxies after 1 billion years.

Large blobs would clean the area with gravity, creating enough pressure to conduct fusion up to Iron, and create stars after 1 million years. They had differing sizes. The large stars burn out the middle and cools with Iron. This implodes creating a supernova which forms all the elements to Uranium. Then it explodes because of the emense pressures and forms nebulas. The nebulas make new stars. If it was 10 times as big as our sun, the core can turn into a black hole, or it'll turn into a neutron star. During the early universe this happened a lot. Today, the temperature has dropped to 2.7 K.

Class Discussion 9-4-96

Matter has weight and takes volume. Gravity affects mass, but not energy. All masses attract each other using gravity. Energy is not attracted by other energy. Light is bent but the space itself is curved.

Post Big Bang phenomenon created elements which are stuff that is composed of only one type of atom. They can exist alone but often combine to form compounds. The rearrangement in the compounds are chemical reactions. There is also a different reaction called a physical reaction which leaves the molecules alone. Generally energy is either required or produced in a chemical process. A substance is composed of pure compounds. When there is more than one compound, even when dissolved, is a mixture. The dissolved mixtures are homogeneous, or same throughout, and is also a solution.

Experiment 2 9-5-96

We examined solubility, magnetic response, color, and state of iron, sand, salt, sugar, baking soda, and magnsium. Then we did a mixuter with salt, sand, and water. We also burned magnesium and sugar and tested the solubility of the products. We also subjected magnesium, the burn products, and baking soda to HCl.

The general purpose was to distinguish from chemical and physical change. Physical change allows the substance to remain itself and change back; chemical change changes its properties.

Scientific Measurement

Topics:

  1. The Imporance of Measurement
  2. Accuracy and Precision
  3. Significant Figures in Measurements
  4. Significan Figures in Calculation
  5. The Metric System
  6. Units of Length
  7. Units of Volume
  8. Units of Mass
  9. Measuring Density
  10. Specific Gravity
  11. Measuring Temperature
  12. Measuring Heat
  13. Specific Heat Capacity

There are quantitative, or definate, and qualitative, or descriptive, measurements. (Lavoisier debunked the ancient theory of phlogiston, fire stuff.)

Accuracy determines how close the measurement is to the actual value. Precision is the reproducibility of the measurement. Significant figures refer to the known accurate digits plus the last uncertain digit. The least accurate measurement dictates the round off point. Scientific notatation, modifies a number such that it is between 0 and 10, multiplied by some power of 10. This makes every digit in the coefficient significant.

The general measurement standard is the metric system. This system was made in 1790 as Le Système International d'Unités or SI, or Internation System of Units. Length is measured in meters. Volume, or a measurement of space, is technically in cubic meters, but often is mentioned in liters.

Weight is not mass but a force. Mass is constant regardless of the acceleration due to gravity. A kilogram and a gram are the standard mass units defined as one liter and one centimeter cubed of water at 4 degrees celsius.

Density is the ration of the mass of an object to its volume. This changes with the temperature as the volume expands and contracts. This also allows stuff to float. Specific gravity, or the ratio of desities, has no units.

Heat is different from Temperature in that heat is energy and temperature is the transfer of energy.

"Specific Gravity is the comparison of the densities of asubstance to the density of a reference substance, usually at the same temperature," and as a ratio has no units. It is normally measured with a hydrometer, which has a float and when is filled with liquid, the level at which the float is determine the reading.

The hotness of something determines its temperature. When two objects of different temperature touch, there is a heat transfer. Because material expands and contracts, temerature can be measured using liquid thermometers. The Celsius scale is one measurement system and is very similar to the Kelvin scale where absolute zero is zero Kelvin. There are bimetalic strips, thermosisters, liquid crystals, and thermocouples.

Heat is energy and measured in joules. It is also measured in calories defined as the amount of heat to raise one gram of water 1 degree celsius. The amount of heat require to change an object's temperature is called heat capacity which varies with mass. Specific heat capacity or specific heat is what a fixed amount of mass needs to raise a fixed amount of temperature. The equation is h=mct (c is written s by class convention). Specific heat is measured in (cal/(kg x C)) or (J / (kg x C)). There are 4.18 Joules per calorie.

Problem Solving in Chemistry

Word Problems sections is an encourager. Chemical technicians are cool.

  1. Identify the unknown
  2. Identify what is known or given
  3. Plan a solution
  4. Do the calculations
  5. Check your work and units

Conversion factors are the ratio between equal measures (obviously 1). Dimensional anlysis checks the units and dimensions of the answer. The book also equates this to factor-label unit conversion.

Converting Between Units is easily done using factor-label. Multistep problems are just like conversions with more stuff. It is also important to control your varibles in experiments. Converting comples units is just like repeating the single units over and over.

Atomic Structure

Atoms

An atom is "the smallest particle of an element that retains the properties of that element." It includes Dalton's atomic theory.

  1. All elemetns are composed of tiny indivisible particles named atoms.
  2. Atoms of the same elements are identical. The atoms of any one element are different from those of any other element.
  3. Atoms of different elements can combine with one another in simple whole numbers.
  4. Chemical reactions occur when atoms are separated , joined, or rearranged. However, atoms of one element are not changed into atoms of another by a chemical reaction.

John Dalton proved the law of proportions for compounds. He also said that atoms were indestructable and there always was a one to one compound.

Electrons, Protons, and Neutrons

Atoms are composed of electrons, negatively charged, protons, positively chargered, and neutrons, no charge. Scientists could make a beam of electrons called a cathode ray. The discovery of the nucleus occured with the shoot the alpha particle through the gold foil experient in 1911.

The Structure of the Atom

"The nucleus of an atom is composed of Protons and neutrons." The number of protons determins the element. The subatomic particles did not exist that much in normal space, they were freaks of nature. To create the high energy collisions to create these elusive particles, scientists build accelerators which created the lepton family comprised of electrons, mu-mesons (muon), tau-meson, and three neutrinos. They are involved in radioactive decay. Leptons seem to be the simplest particles which act on electroweak force. The hadrons using the strong force, are composed of quarks called up, don, top, bottom, strange and charm. These have charges like +2/3, -1/3. They have anti-particles. They have weightless particles like gluons, photons, and others that have two forces like bosons. There are in sum 6 quarks, 6 leptons, 24 antiparticles, 8 gluons, W & Z Bosons, and the photon.

Atomic Number

The atomic number is the number of protons the element has.

Mass Number

To determine the mass of an atom, scientists use the amu or atmoic mass unit which is defined as one tweleth the mass of a carbon 12 atom. The mass number counts the weight of mainly the neutrons and protons.

Isotopes & Atomic Mass

Isotopes change elements only in the number of neutrons. Atomic mass is the weighted average of all the isotopes of the element. A mass spectrometer makes a thin gaseous form of the substance and slings it electrically and inertially filters it.

Class 9-12-96

Electrons were the first things pulled off atoms using high temperatures (3000°). The Curies also investigated the nucleus with radioactive things. Rutherford found the alpha particle, two neutrons and two protons, a helium ion. Tons of them went through the foil, but some bounced back.

Class 9-18-96

The book approaches the atoms by discovery rather than creation. In 500 BC, Democratis suggested that matter could only by divided finitely. Dalton found the constant ratio for the compounds. He was wrong that there was only one way for the combination of matter. He reformulated it to say that there are whole number factors. Thus, the gunk must be broken into basic particles. Since then they were able to put electrodes into a near vaccuum bottle (JJ Thompson). The electrons were pulled off with just a thousand volts. The neutral atoms had split! There were two theories for the remainder, where there was a positive / negative pie and the other where the positive was centralized with negative next to it.

The next thing was radioactive stuff. There were three rays, alpha (helium nucleus), beta , and gamma rays. Rutherford shot alphas into the gold foil. If it is a pudding, it should be uniform. If it is solid positive charged particles, it should reflect.

Atomic Structure

One proton or one neutron weighs one AMU. The atomic number is equal to the number of protons and electrons in a neutral atom.

Class 9-19-96

They found the nucleus had too much mass for just having protons. They couldn't extract the neutrons until the 20th century. The neutrons are variable. The symbol 1224Mg gives the 24 mass number and 12 protons, electrons, atomic number. The atomic mass is the weighted average of the isotopes.

Chemical Names and Formulas

The Periodic Table

The periodic table arranges the elements by their properties. Each column on the table is a group desigated by a letter and a number. The A group does not include the transition metals and are the representative elements which show the range of chemical properties. Metals are on the left side and they are shiny and conduct electricity and can by pounded and extruded. The transition metals are in group B and contain an inner set called the rare earths. Non-metals are not metals and some are gases and stuff with the stinky exception of hydrogen. There are also semi-metals or metalloids which have some metal properties.

Atoms and Ions & Compounds

Ions are atoms that have gained or lost electrons and thus charge. There are cation, positive, and anions, negative. Compounds will form only in fixed ratios of elements or the law of definite proportions. This makes sure that each molecule, or stable particle, will have the same number of atoms. "Compounds that are composed of molecules are molecular compounds." Ionic compounds form when an atom gives an electron to a neighbor who gains it.

Chemical Formulas

A chemical formula gives number and type of atom information about a substance. Similarly a molecular formula shows atom number and type information on a molecule or compound. This tells nothing of the structure. Chemists also use a formula unit which reduces the ratios to lowest whole numbers.

The Law of Multiple Proportions & Ionic Charges of the Elements & Polyatomic Ions & Common and Systematic Names

The law of multiple proportions says that when two elements for a compoud, they mix in a fixed ratio. It is easy to get the charges of the group A elements, the transition metals however have multiple charges denoted by -ous and -ic or roman numerals. Polyatomic ions are compounds that carry a charge, so there. Bases are compounds that give off OH-. Most polyatomic ions end in -ite (one less oxygen than -ate) or -ate but the anions generated end in -ide. The people named compounds after discoverors or their qualities and stuff, but now they use the standard di-, mono-, tri- -ide naming scheme for most stuff (exception: water).

Pharmacy from Scheel to the Present

Originally they used leaves and stuff to make drugs. Scheele conducted experiements in 1756. He isolated elements in the time of the fire, water, air thing. He duplicated synthetically, a naturally occuring chemical.

Writing Formulas for Binary Ionic Compounds & Naming Them

Composed of two compounds, binary compounds are composed of a monoatomic cation and a monatomic anion. They are electrically neutral. There exists confusion as CuO can also be Cu2O because of Copper(I) and Copper(II). The roman numerals are derived as neccessary and each formula must be evaluated.

Ternary Ionic Compounds

Ternary compounds, which contain three elements, contain polyatomic ions which are balenced using parenthesis and can be identified by the -ate or -ite endings.

Binary Molecular Compounds & Acids

Using the prefixes (p105), we can name the compound using the names with the last one modified to -ide. Acids are compounds when dissolved in water give hydrogen ions, and are written H(). The nomenclature is as follows:

Summary is on Text p107. Chemistry Data Banks store compound information. One example is CIS, Chemical Information System (1971), which has dial-up access. These are also used to fight chemical spills, fires, and poisoning.

Class 9-20-96: Atom Struct

After 300,000 since the big bang, the electrons calmed down to form hydrogen atoms with shells orbitals. Each shell has a capacity. The structure is related to the periodic table because the columns tell the outer shell electron number. Transition metals is where the 3rd or higher shell that is not outer shell can hold upto 18 electrons.

Compounds are formed by sharing, giving, or getting electrons. The outer shell in this sense are the movers and shakers. The shell wants eight or zero electrons on in compounds. An ionic compound of Li, F is litium flouride. This is a salt.

Movie: 9-23-96

Chemistry and the periodic table showed that the periodic table shows metals, nonmetals, and metalloids. It also explained that there is a relationship between groups and melting point, conductivity and ion potential. The orbitals are subdivided into sub-orbitals in s, p, d, f. S is spherica, p is a infinity-iod, d is a broken infinity-oid with a torus. The ordering of energy levels are done with a table with the major levels on the vertically increasing down and the sub levels at the top from s.-f. then the filling sequence follows the diagonals to the SW.

Class 9-24-96

In the Litium atom, there are three neutrons, three protons, and three orbiting neutrons two in the inner and one in the outer. The outer shell wants eight or none. Use dots around the symbol to show outer shell electrons. This ionizes and creates an ionic compound. It loses all its properties. The positive charges gets negatives on all six sides and this continues to crystalize. To name compounds, we take the first element is the metal or positive ion then the second element gets an -ide ending for a two element compound. When these ionic compounds, the ions separate between water molecules. The smallest thingy for the compound is called a formula unit.

Class 9-25-96

Valence is the ionic charge and is also known as the oxidation state. The transition metals have multiple oxidation states and are written like Iron(II) to denote the state. They also have a -ous (lower) and -ic (higher) valence numbering stuff.

Class 9-26-96: Ternary Compounds

Ternaries are stuff with three atoms. The atoms also start sharing electrons in polyatomic ions, for example PO43+ and SO42- (sufate). They are a non-metal and oxygen, normally, consisting of more than one element and is charged, behaving like a molecule.


Polyatomic Ion      Name           

SO42-               Sulfate        

PO43-               Phosphate      

ClO3-               Chlorate       

NO3-                Nitrate        

CO32-               Carbonate      

CrO42-              Chromate*      

C2H3O2-             Acetate*       

NH4+                Ammonium*      

OH-                 Hydroxide*     



Table 2: Polyatomic Ions

* These elements do not have the -ite thing listed on the table. The acidification of the polyatomics is important. You can add hydrogen to partially neutralize the charge such as hydrogen phosphate (HPO42-). Then we add another hydrogen creating dihydrogen phosphate H2PO4. Then the final hydrogen creates phosphoric acid H3PO4.

Class 9-27-96

ClO3- is chlorate, and you may remove an oxygen atom without changing the charge. Now it is ClO2-, chlorite. When we take away one more oxygen, we get ClO- or hypochlorite. If you add oxygen to chlorate, you get hyperchlorate or perchlorate (ClO4-). These polyatomics can be used like element in compound naming.

Class 10-1-96

The charges must be balenced. This is named using the -ide convention, but no mono-, di-, tri-, tetra-, penta-, hexa-, septa-, octo-, nona-, and deca-. There are roman numerals for multiple permutation. The different from ionic bonds is covalent bond which forms molecules. This is where they share electrons. This occurs with non-metal compounds. The polyatomic ions are mainly -ate and -ite. Adding hydrogen to an -ate gives an -ic and the -ite goes to -ous. The hypo- and (hy)per- remains. The element itself is hydro- -ic.

Class 10-2-96

Type                                    Compound                                 

I                                       Ionic with Representative Elements (no   
                                        transition metals)                       

II                                      Ionic with Transition Elements           

III                                     Covelent                                 


Table 3: Compound types

IMPORTANT NOTE: Ionic compounds do NOT have the di-, mono- prefixes. Polyatomic ions have used (#33 in Ch. 5) di- prefixes BUT they are DIFFERENT ions!

Chemical Quantities

We face the challenge of measuring matter. Chemists use moles (6.02*10^23 particles = Avogardro's Number) which count representative particles, or the particles like molecules, ions, and atoms that tend to react with others. Most elements are atoms except for H, NN, O, F, Cl, Br, and I which are diatomic. The gram atomic mass (gam) is "the number of grams of an element that is numerically equal to the atomic mass in amu." It is also equal to one mole of particles of a monoatomic element. Similarly the gram molecular mass (gmm) is the mass of one mole of any molecular compound. For ionic compounds which have two or more representative particles, it is the gram formula mass (gfm). All of these definitions are sometimes reduced to molar mass. Using these things backward, one can find the gram weight of something measured in moles.

One mole of any gas a standard temperature and pressure (STP) of 1 atm and 0° C takes up 22.4 L. Given a density at STP, one can find the gfm (weight of the formula). Thus we have examined the mol's relation to volume, particles, and mass. Avogadro unified Gay-Lussac's experiments where one liter of oxygen and two liters of hyrdrogen formed two liters of water vapor. They acted more alike in terms of molecules. They found the diatomicity of oxygen using the one molecule O and two molecule H forms two molecules of water. Percent composition is done by mass.

"The empirical formula gives the lowes whole-number ratio of elements in a compound." We will take the example of 25.9% of Nitrogen and 74.1% of Oxygen. We can assume without loss of generality that our sample is 100g and thus we have 25.9 g Nitrogen and 74.1 g Oxygen. Now we convert to mols using by multiplying the masses by the gram to mole conversion (multiply by 1 mol / molar weight of the element). Now we have a ratio and divide through by the smallest number and fractionalize. To get the molecular formula, we must multiply by some constant. We just need the gram formula mass to find the formula.

Chemical Reactions

Chemical equations have reactants on the left of an arrow and products on the right. There is the unbalenced equation which is called a skeleton equation. There are catalysts which speed up reations without changing themselves. One can use = instead of the arrow. In a reversible reation, there is a double arrow. A down arrow is used to denote a product that is a precipitate. An up arrow similarly denotes a gaseous product. Dissolved things are (aq) while solids, liquids and gases are (s), (l) and (g). A delta or "heat" on the arrow says that heat is needed. You can also put a catalyst over the arrow. Balencing equations makes sure that both sides have the same amount of atoms.

One could do all possible reactions in a laboratory, but that's too hard so one should be able to predict outcomes. A simple one is a combination reation where some stuff combines. Decomposition reactions are the opposite to the combination reaction; only they normally require energy. However, it is hard to predict the products.

A more complicated reation is the single replacement reaction where some atom replaces another. This is activity is shown by an activity series of metals (Table 7.2, p. 155). This lists stuff increasing level of actvity, and this chart can be made for the nonmetal halogens.

There are double replacement reactions which exchange positive ions between compounds. It must produce a precipitate, gas, or molecular compound like water. Most chemistry at the high school level is wet and qualitative. The quantitative wet chemistry requires really precise mesurements using instruments. They uses quantities around 0.001 down to 0.000001 with mass spectrometers and spectral analysis.

A combustion reaction occurs when oxygen reacts with antoher substance producing heat and light. A candle is a complicated reaction. It melts and vaporizes was. The air is mixed and burns, some doesn't burn completely and heats releasing the yellow light. The upper part burns it completely with more oxygen. The bunsen burner mixes the gases ahead of time and burns more completely. There is a final reaction called an oxygen reduction reaction.

Firefighting cuts off heat, oxygen, or fuel. Class A fires are standard wood fires that can use water. Class B fires are liquid fuel and class C fires are electrical and class D fires are with burning metal. Carbon dioxide is used for B & C. Baking soda is used in dry chemical powder extinguishers and monoammonium phosphate is commonly used for A & B & C extinguishers in households.

Class 10-23-96

The double replacement reaction requires that something gaseous, non-soluble, or another thing with greater attraction be created (Lab Workbook P.317). This is like the single replacement reaction which requires the thing replacing an element to be of a higher reactivity (Textbook P.155).

Class 10-28-96: Double Decomposition

Double replacement needs the insoluble pricipitate, gas or molecule. The solubility is generally determined by higher charges such as AlP which has 3 (2 works too) charges or by larger atoms like AgCl (Silver Chloride is insoluble). An exception is the hydroxide which form insoluble compounds with the double charges. These formulas could be written in ionic forms where ions are written alone. This form results in two ions that don't do anything, so you can write the net ionic form which gets rid of the "useless" ions.

There is another kind of reaction. Such as HCl + KOH -> KCl + H20. This is the formation of the molecule. Combustion decomposes to water and carbon dioxide.

Stoichiometry

Stoichiometry is the calculation of quantities in chemical equations. Reading a chemical equation, one can find the number of particles and moles, mass, and volume. Of these factors, only mass and atoms are conserved during reactions. One must measure quantities of stuff in grams then convert to mols. Similarly one can document a reaction in particles, mass or STP Liters. Since chemical reactions require ratios determined by the balencing, one can be limited by the amount of a material that one has and this is a limiting reagent. If one has too much of something this is an excess reagent. In a chemical equation, there is a theoretic yield from the formulas. In a laboratory there is the actual yield from an experiment. The percent yield is what part of the actual stuff is the theory say. "Exothermic reactions release energy in the form of heat." This is from the energy in the chemical bonds. There are also chemical reactions which require and take in heat; these are called endothermic reactions. By writing the heat things down, we get a thermochemical equation. To measure heat, we can melt ice or use a foam cup. The foam cup is not closed and loses heat. Advanced calorimeters have a closed chamber, stirer and thermometer. The amount of heat that something has at a given temperature and pressure is enthalpy, symbolized by an H. When a reaction occurs and heat is given or taken, it is called the heat of reaction. When everything is burned, they change the name to heat of combustion. The enthalpy and delta-H are arbitarily set to zero when the element is in its pure, natural form (diatomics are paired as usual). "The delta-H for a reaction in which 1 mol of a compound is formed from its elements is the standard heat of formation." The standards for enthalpy in terms of temperature and pressure is 25° C and 1 atm.

The States of Matter

Gases

The kinetic theory of matter is the theory that all particles of matter are constantly in motion thus gases are spread far apart and have no particulate attractions, move rapidly, and are bouncy when they collide. Kinetic energy of a particle is given by . The particles have different kinetic energies, but form a bell curve that spreads wider as it gets higher. There is no upper limit on this energy, but there is a lower limit, absolute zero.

Pressure is the amount of force per a unit area and is measured in Pascals (N/m2) mmHg (one millimeter of mercury, as pressre does not depend on the crossection of the mercury column), and atm (one standard atmosphere). Gas pressure is caused by tons of gas molecule collisions. Without these collisions, there is a vacuum. Atmospheric pressure (101.3 kPa) decreases with altitude and changes slightly with the weather, making our barometers. Ancient barometers uses a long tube of mercury that was inverted into a dish of mercury while today's barometers uses a chamber with a diaphram.

Avogardro's hypothesis stated, "equal volues of gases at the same temperature and pressure contain equal numbers of particles."

Liquids

Liquids are weakly attractive but are free to move. Vaporization is where stuff goes away even when it's not boiling which is commonly called evaporation. As you heat a liquid evaporation rate increases, but in a closed container, the vapor pressure caused by the freed particles increases and will reach equilibrium. "The boiling point is the temperature at which the vapor pressure of the liquid is just equal to the external pressure." The normal boiling point is placed under a pressure of 1 atm. Because the liquid remains at the boiling point until all of the liquid is gone, boiling is a cooling process.

Liquid crystals are rods and are orderly. Some are nematic, used in computer screens, and are parallel but not lined up. Others are smectic and are lined up and parallel. The final type is Cholesteric where they are parallel to others of their type but tilted. Smetic and Cholesteric are used in liquid crystal thermometers.

Class 11-13-96

The liquids are characterized by the molecules touching but sliding past one another. There is nothing to hold it in a fixed matrix, so it flows. The kinetic energy is still present, which grows as it is heated. The molecules go faster and faster breaking off sometimes. Some will move slower while others move faster. The average is measured using a thermometer. The fastest ones are fast enough to break from the surface and turn into a gas.

However, if the container is closed and the hot ones jump out, there forms a vapor above the liquid. This is evaporation. The liquid has cooled as the average kinetic energy is gone. At a certain point, the vapor will create a certain pressure and some will condense out and other replace them. Pressure has an important factor on this and this pressure is called vapor pressure. This depends on the temperature and allows more liquid molecules to go into the vapor state. This is exponential or quadratic to the temperature. Vapor pressure should be zero as a solid and should equal the atmospheric, or ambient pressure, at the boiling point. This varience actually should be the other way around, the boiling point depends on pressure.

Solids

Solids are organized and the vibrations of the matrixied molecules eventually break free at the melting point. Ionics have high melting points. Most solids are crystaline and have regular patters of arrangement. THe smallest unit of a crytsal is a unit cell. There are disorganized solids called amophorous. Other "solids" are supercooled liquids.

Class 11-13-96

The molecules are still in relation to each other. They retain their shape. The motion is still in vibration. To keep these atoms on a matrix, there is at first the ionic relation. Each atom surrounds itself with opposite charges and this holds it together. There are the three types of cubics: simple, face-centered, body-centered. The ions have to pack in the densely while taking into account that opposites attract. The hexagonal crystal structure is right and planar.

Phase Changes

Phase changes occur as materials pass through states. They maintain the respective changing points until all the material has changed state. The changing from solid directly to gas or vice versa is called sublimation.

These changes require energy and the energy require depends on mass. For melting it is called heat of fusion and for freezing it is called the heat of solidification. Similarly the heat of vaporization and the heat of condensation is for liquid and gases.

Plasma is where atoms lose there electrons. Flames, fluorescent lights, and other stuff are weakly ionized and plasma. The highly ionized plasma can only be made at about 50 thousand kelvin to 100 million kelvin (in the sun). They try to use toruses to contain these high temperatures. They can be used to rough up metals and can conduct electricity and be effecient motors. They are trying to make a magnetohydrodynamic power generator (MHD). They burn stuff to make ionized gas and pass this through a magnetic field which makes energy.

The Behavior of Gases

Gases can be compressed by moving more of them in the same volume. They like to expand outward until they are equally distributed. Halving the volume has the same effect as doubling the amount of gas. Gases heat when they are compressed and cool when they are released. Similarly with temperature, halving it (Kelvins) halves the pressure. We will use ideal gases, where they follow all the gas rules at all conditions. Real gases change state every so often. Dalton's Law of partial pressures says that in a mixture of gases at a given constant temperature the pressure is the sum of the partial pressures of each gas.

"Boyle's Law states that for a given mass of gas at constant temperature, the volume of the gas varies inversly with pressure." SCUBA, self-contained underwater breathing apparatus, enabled divers to be free underwater and not be tethered with air hoses. However, divers must worry about pressure which increases 1 atm per 10 m. This makes it really hard to breathe but the SCUBA device delivers air at that pressure. The mixture of gasses are also important as the partial pressures have a level of toxicity. Decompression plays a role during the as gases expand in the blood stream and also in the lungs, causing ruptures. Charles' law relates gas volume to absolute temperature (varies directly). The Gay-Lussac law states the Charles' law for pressure. Liquifying gasses can be accomplished by pressurizing the gas then releasing the pressure, creating a temperature loss. Once you do this enough, you can liquify a gas.

These laws can be combined in the (surprise!) combined gas law. By adding an n term which give the number of moles of gunk, we can get the ideal gas law (when expanded, we get PV=NRT). We also note that one mol, will have a volume of 22.4 L under STP. Thus pressure, temperature, number of molecules, and volume are all constant. The ratio has to be constant and is named R=0.0821 , the ideal gas constant. An explosion occures when something is quickly changed within or to the gaseous state which takes up tons of room. There is an initial shock wave that is created from the expanding mass. Alfred Nobel manufacuter nitroglycerine for the mining industry, a oxygenated explosive compound that could detonate on a slight vibration. He eventually, by accident found dynamite, nitrogylcerin soaked diatomaceous earth, which was stable, easy, and just as effective an explosive.

The gas laws aren't real because the molecules have some stickiness necessary for liquifaction and they take up room or they wouldn't be mass. Thus they can deviate from the ideal gas laws. "Diffusion is the tendency of molecules and ions to move toward areas of lower concentration until the concentration is uniform throughout the system." Graham studied effusion, difussion through a small hole. He found the Graham's law of effusion that the rate, "is inversely proportional to the square root of its formula mass."

Electrons in Atoms

There was the initial theory of the individible atom, then the Thompson development of the electron stuck in atom dough. Later Rutherford found the nucleus and positive charges which posed the question of why the atom didn't collapse. The Bohr model tried to put the electrons spinning in circles or energy levels. To move between levels, a quantum of energy is required.

Later the quantum mechanical model was developed. Unfortunately, this model is nearly all mathematical and cannot be visualized. They have a blurry cloud of probablility.

There are priniciple energy levels which are numbered. Each level has atomic orbitals which determine where the electron probably is. The first level as an s orbital, then the second has the s and the three p axes orbitals. The thirld level adds five d orbitals which are x shaped in the xy, yz, xz, x2-y2, and z2 orientations. The fourth level adds seven f orbitals. Each orbital takes two electrons, each must have the opposite spin of the other. The spins make magnets.

These orbitals are nothing without learning the configurations of the electrons (electron configurations) or how they are arraigned in a given atom. There is the Aufbau principle where the electrons enter the lowest levels first. The diagram on 251 will help as the 4s orbital is lower than the 3d orbital and similarly the 4f orbital is lower than the 5d orbital. The Pauli excusion principle tells us that each orbital can have two electrons and they must spin opposite each other. Finally Hund's rule states that each orbital (the ones that are symmetric) must contain parallel spins before they can get opposite ones. You write the contents of orbitals like 1s1 where the upper number is the number of electrons and the coefficient is the level and the leter is the orbital. These are written in order of the sublevels and levels, not the orbital precendence. There are exceptions like Chromium with one in the 4s shell and copper with one in the 4s shell.

There were the two wave and particle ideas in 1900. There was the wave model which said that electromagnetic radiation travels at 3.0x1010 cm/s in space. There is the amplitude of the wave which determines how "big" the wave is. There is also the wavelength of the wave which is how "long" the wave is. The frequency determines how many waves go per a second. If there is a constant speed, as the wavelength increases the wavelength decreases. Frequency is measured in hertz or cycles per a second. The different frequencies determine the "color" of the waves and thus yields a spectrum of colors. When a gas of an element is heated and passed through an electric current, it emits certain wavelengths of light which are called the atomic emission spectrum.

There was the idea that energy was continuous and you could give infinately small amounts of energy. However, it was shown that you couldn't do that so the guy who found that out, Planck, had a constant named after him, Planck's constant, 6.6161x10-34 J.

Einstein took the idea of quanta and said that light was made of photons. There was a disparity with the particulate and wave theories which were eventually melded. The photoelectric effect is the result of electrons, also known as photoelectrons, which are ejected by metal when light is shone on them. Classical physics failed here. Einstein found a threshold level at which this occured.

Digression

The neon lights are where electrons jump orbitals. Incandescent bulbs heat up filaments to make light. Flourescents function like neon lights and are more effecient because they run cooler.

You can determine some metals by dissoling it in hydrochloric acid and dipping it wit a nichrome or platinum wire and placing it in the Bunsen burener flame. It was perfected by Robert Bunsen. This gives certain colors for different chemicals.

Spectroscopy is the best way to identify chemicals. There is flame spectrophotometry which uses a flame. There is absorption spectrum which uses the characteristics of the material to absorb monochromatic light. There is also a moelcular fingerprint from the vibrations as a result of the excited electrons. The initial energy comes from a lamp, spark, electric arc, flame, laser, X-ray, or radioactive substances.

Chemical Periodicity

The mid eighteen hundreds needed some way of catagorizing the 70 elements found. Mendeleev devised a way of tabeling these elements to show their similarities. Moseley later catagorized them by atomic number. They wrote books and attended conferences on the naming of elements. By organizing the data, Mendeleev was able to predict elements characteristics by establishing a method of deductive reasoning from established principles.

There are horizontal rows called periods in the modern table. They are also arraigned vertically in groups which allows periodic laws to be found. The noble gases are filled in their outer S and P levels. The representative elements are the elements that are having their p levels filled and the transition metals are the ones having their d levels filled. The inner transition metals are having their f levels filled.

The covalent atomic radius, the volume of the atom increases as you go down and decreases as you go right. It increases as you go right because the protons get more attraction and the shell is not complete. The sideways forces by the electrons in the same level are not enough to keep the thing big. As you go down, the lower levels push out on the electrons making the radius bigger. This is a "shield."

The ionization energy decreases as you go down and increases as you go right. This is the energy required to separate an electron from the atom. Electron affinity, the attraction of the atom to other electrons, decreases as you go down and increases as you go right. The ionic radius decreases due to the same reasons as the shielding in the covalent atomic radius. The cation, positive, decrease while the negatives increase. This maintains the basic relationship in the atomic radiuses. Electronegativity is the attraction that an element has to electrons when it is covelentized. This is similar to the electron affinity and increases to the right and decreases down.

Lab Safety 9-5-96