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AP chemistry videos
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AP chemistry videos
001 - Elements and Molecules
In this video Paul Andersen explains how elements and molecules are made of atoms. In a pure sample of a pure substance the average mass remains the same. If more than one atom is found in a molecule the ration of average masses remains the same. If two elements have the same atoms but differ in arrangement the ratio of average masses will vary.
In this video Paul Andersen explains how chemical analysis is important in determining the composition, purity and empirical formula of a compound. An empirical formula determination problem is also included.
003 - The Mole
In this video Paul Andersen defines and explains the importance of the mole. The mole is simply a number (like a dozen) used to express the massive number of atoms in matter. It serves as a bridge between the mass of a compound and the number of particles. It is represented in chemical reactions as the coefficients before reactants and products.
THE ANSWER: 1.91 x 10^22 molecules of Glucose
004 - Coulomb's Law
In this video Paul Andersen explains how we can use Coulomb's law to predict the structure of atoms. These predictions can be verified through the use of Photoelectron Spectroscopy (PES). Electron's are help around the nucleus because of differences in charge. As the atoms become larger the charges change and so do the structures.
005 - Electron Configuration
In this video Paul Andersen explains how to write out the electron configuration for atoms on the periodic table. More importantly he shows you why electrons arrange themselves in shells, subshells and orbitals by using Coulomb's law and studying the first ionization energies of different atoms.
Cl - [Ne] 3s^2 3p^5
Ag - [Kr] 4d^10 5s^1 - Did you get [Kr] 5s^2 4d^9? There are a few exceptions to this law. Most of them are found in the f-block metals and they are not of much chemical significance.
006 - Periodicity
In this video Paul Andersen explains why atoms in the periodic table show trends in ionization energy, atomic radii, electronegativity and charge. All of these trends are explained through Coulomb's Law. A brief description of Dmitri Mendeleev and the power of predictability are included.
007 - Quantum Mechanical Model
In this video Paul Andersen explains how the quantum mechanical model of the atom refined the shell model. Uncertainty of the position of the electron as well as spin forces chemists to create an improved model. In this model the position of the electron is determined through quantum numbers.
008 - Atomic Models
In this video Paul Andersen explains how the atomic model has changed over time. A model is simply a theoretical construct of phenomenon and so when we receive new data we may have to refine our model. Ionization energy data resulted in the formation of a quantum model that more accurately reflected the atom.
009 - Mass Spectrometry
In this video Paul Andersen explains how a spectrometer was used to identify the presence of isotopes. This modified Dalton's original atomic theory because atoms of the same element had different masses. The functional parts of a mass spectrometer are detailed including the ionizer, mass analyzer and the detector. A simulation of Chlorine isotopes along with an average atomic mass calculation is included.
010 - Light and Matter
In this video Paul Andersen explains why light is important in probing matter. Light travels in photons and the energy of individual photons is determined by Planck's equation. Infrared spectroscopy is useful in detecting the vibrations within a molecule and can therefore give more information on the bond types. Ultraviolet and visible spectroscopy is useful in detecting the electronic structure of matter. Beer-Lambert Law describes how increasing concentration increases the absorbance of a solution.
011 - Symbolic Representations
In this video Paul Andersen explains how the conservation of matter can be displayed with both symbolic representations and particulate drawings. A simple conservation of matter problem is also included.
012 - Conservation of Atoms
In this video Paul Andersen explains how atoms are conserved in a chemical reaction. This can be seen in a chemical equation where the subscripts represent the atoms in the molecule and the coefficients represent the molecules. The mass of an anylate can be determined through both gravimetric analysis and a titration.
013 - Solids and Liquids
In this video Paul Andersen compares and contrasts the properties of solids and liquids. Solids have a more organized structure which can either be amorphous or crystalline. In liquids the intermolecular forces are lower and so the molecules can show translation. Some of the properties that can be observed in liquids are viscosity, surface pressure and volumes of mixing.
014 - Gases
In this video Paul Andersen explains how gases differ from the other phases of matter. An ideal gas is a model that allows scientists to predict the movement of gas under varying pressure, temperature and volume. A description of both the kinetic molecular theory and Maxwell-Boltzmann Distribution are included. As a gas approaches condensation some of the ideal gas laws fall apart.
015 - Solutions
In this video Paul Andersen explains the important properties of solutions. A solution can be either a solid, liquid or gas but it must be homogeneous in nature. The solutes can not be separated with a filter and so either chromatography or distillation must be used. Molarity is the number of moles of a solute in a solution. A simple molar solution preparation is also included.
016 - London Dispersion Forces
In this video Paul Andersen describes the positive force intermolecular forces found between all atoms and molecules. As electrons are distributed unevenly it creates instantaneous dipoles which hold molecules together. This force even holds uncharged atoms (like Noble gases) together. London dispersion forces increase as surface area, molecule sizing and pi bonding increases.
017 - Dipole Forces
In this video Paul Andersen describes the intermolecular forces associated with dipoles. A dipole is a molecule that has split charge. Dipole may form associations with other dipoles, induced dipoles or ions. An important type of dipole-dipole forces are hydrogen bonds.
018 - Intermolecular Forces
In this video Paul Andersen explains how intermolecular forces differ from intramolecular forces. He then explains how differences in these forces account for different properties in solid, liquids and gases. Some of these properties include the boiling point, melting point, surface tension, capillary action and miscibility. Intermolecular forces between gas molecules creates variation from ideal gas law.
019 - Covalent Bonding
In this video Paul Andersen explains how covalent bonds form between atoms that are sharing electrons. Atoms that have the same electronegativity create nonpolar covalent bonds. The bond energy and bond length can be determined by graphing the potential energy versus the distance between atoms. Atoms that share electrons unequally form nonpolar covalent bonds.
020 - Ionic Bonding
In this video Paul Andersen explains how ionic solids form when cations and anions are attracted. When atoms lose or gain electrons they form ions. The strength of the attraction between ions is based on the amount of charge and the distance between the ions.
021 - Metallic Bonding
In this video Paul Andersen explains how metallic bonding structure creates the different properties of metals. The electron sea model explains how the positive nuclei are locked into a negative sea of delocalized electrons. This sharing of electrons creates metals that are good conductors, malleable, ductile and non-volatile. A shell model can be used to explain certain properties of metals (like melting point).
022 - Lewis Diagrams and VSEPR Models
In this video Paul Andersen explains how you can use Lewis Diagrams and VSEPR Models to make predictions about molecules. The Lewis diagrams are a two-dimensional representations of covalent bonds and the VSEPR models show how the molecule could exist in three dimensional space. Pi bonding and odd valence electrons require an extension of this model.
023 - Ionic Solids
In this video Paul Andersen explains how ionic solids form a lattice between cations and anions. According the Coulomb's Law the lattice energy increases as the ions carry a larger charge and are smaller. Some of the properties of ionic solids are high melting point, low vapor pressure, brittleness and the inability to conduct electricity. Ionic compounds can be readily dissolved by polar molecules like water.
024 - Metallic Solids
In this video Paul Andersen explains how metallic solids form when delocalized electrons hold the positive nuclei in an electron sea. This model helps to explain the properties of metals like conductivity, shiny appearance, malleability, ductility, and the ability to form alloys. Alloys can be substitutional or interstitial in nature and can change the chemistry of the metal.
025 - Covalent Network Solids
In this video Paul Andersen explains how covalent network solids form elementally (like graphite) or by combining multiple nonmetals (like quartz). Covalent network solids contain elements from the carbon group because they have four valence electrons and can create three-dimensional shapes. Silicon crystals act as semiconductors and can be either n-type or p-type doped to increase their effectiveness.
026 - Molecular Solids
In this video Paul Andersen describes the structure and explains the properties of molecular solids. High intramolecular forces hold electrons and reduce conductivity, whereas low intermolecular forces decrease the melting point. Important polymers can be formed from monomers and have both commercial and biological value.
027 - Molecular, Ionic and, Net Ionic Equations
In this video Paul Andersen shows you how to write balanced equations that describe chemical changes. He then gives you a short introduction to balancing equations and uses the PHET site to practice this skill. In aqueous solutions an ionic equation (or complete ionic equation) is helpful in following the ions. When the spectator ions are removed a net ionic equation can be used to show the chemicals that are actually combining in the reaction.
028 - Stoichiometry
In this video Paul Andersen explains how stoichiometry can be used to quantify differences in chemical reactions. The coefficients in a balanced chemical equation express the mole proportions in that reaction. These values can be used to predict the expected values, determine the limiting reactant, predict the molar mass of gases, determine the percent yield and interpret results from a titration.
029 - Synthesis and Decomposition Reactions
Atoms or molecules combine to form a new compound in a synthesis reaction. Examples include the addition of oxygen to magnesium metal to create magnesium oxide and the addition of carbon dioxide to water to crete carbonic acid. A combine breaks down into new atoms or molecules in a decomposition reaction. Examples include the break down of sodium azide in a airbag or the break down of hydrogen peroxide in your cells. Decomposition reactions will often release heat as bonds are broken and new bonds are formed.
030 - Neutralization Reaction
In a neutralization reaction (or acid-base reaction) a proton is transferred from the Brønsted
Lowry acid to the BrønstedLowry base. Water is amphoteric and so it can serve as either an acid or a base in a neutralization reaction. The strength of an acid or a base is determined by the ability to donate or receive a proton.
031 - Redox Reactions
In this video Paul Andersen explains how redox reactions are driven by the movement of electrons from the substance that is oxidized to the substance that is reduced. Oxidation is the loss of electrons and reduction is the gaining of electrons. Since electrons are not normally displayed in a chemical equation oxidation numbers are important in determining what atom is oxidize and what atom is reduced. Redox reactions are important in energy production and can also be used in basic titrations.
032 - Chemical Change
In this video Paul Andersen explains how chemical differs from physical change. In the laboratory macroscopic observations are used to infer changes at the particulate level. Evidence for chemical change include gas production, change in temperature, change in odor, change in color, and formation of a precipitate.
033 - Endothermic and Exothermic Reactions
In this video Paul Andersen explains how heat can be absorbed in endothermic or released in exothermic reactions. An energy diagram can be used to show energy movements in these reactions and temperature can be used to measure them macroscopically.
034 - Electrochemistry
In this video Paul Andersen explains how electrochemical reactions can separate the reduction and oxidation portions of a redox reactions to generate (or consume) electricity. The half reactions can be analyzed to determine the potential of either a galvanic (voltaic) or an electrolytic cell. The reduction takes place at the cathode and the oxidation takes place at the anode.
035 - The Rate of Reactions
In this video Paul Andersen defines the rate of a reaction as the number of reactants that are consumed during a given period of time. The rate of the reaction can be affected by the type of reaction as well as the concentration, pressure, temperature and surface area.
036 - The Rate Law
Paul Andersen explains how the rate law can be used to determined the speed of a reaction over time. Zeroth-order, first-order and second-order reactions are described as well as the overall rate law of a reaction. The rate of a reaction can be determined experimentally.
037 - The Rate Constant
In this video Paul Andersen describes the characteristics of the rate constant in chemical reactions. The rate constant is highly variable in reactions and must be determined experimentally. The rate constant is dependent on both temperature and the presence of a catalyst. In a first-order reaction the rate constant and the half-life are both independent of the concentration and inversely proportional.
In this video Paul Andersen explains that elementary reactions are steps within a larger reaction mechanism. Colliding molecules require sufficient energy and proper orientation to break bonds and form new bonds. A unimolecular reaction mechanism requires one type of reactant and is a first-order reaction. A bimolecular reactions requires two molecules colliding and is a second-order reaction. Termolecular reactions are rare but are the colliding of three molecules.
039 - Activation Energy
In this video Paul Andersen explains how the activation energy is a measure of the amount of energy required for a chemical reaction to occur. Due to the collision theory the activation energy requires proper energy and orientation of the colliding molecules. The Maxwell-Boltzman distribution can be used to determine the number of particles above and below this point.
040 - The Reaction Path
In this video Paul Andersen explains how the reaction path can be described in an energy profile. Enough energy must be added to reach the activation energy required and stress the bonds. Eventually the bonds break and new bonds are formed. The rate constant is temperature dependent. The Arrhenius equation can be used to calculate the activation energy when the temperature and rate constant are calculated.
041 - Multistep Reactions
In this video Paul Andersen explains how an overall chemical reaction is made up of several elementary steps. The stoichiometry of this equation can be predicted but the rate law must be measured. If the elementary steps of the reaction are determined the rate law of this individual step may be predicted.
042 - The Rate Limiting Step
In this video Paul Andersen explains why the slowest elementary step in a chemical reaction is the rate-limiting step. This step can be used to determine the overall rate law of the chemical reaction.
043 - Reaction Intermediates
In this video Paul Andersen explains how reaction intermediates are created in elementary steps and may not appear as either a reactant or product. Experimentation is used in Chemistry to identify reaction intermediates.
044 - Catalysts
Paul Andersen explains how catalysts can speed up a reaction without being consumed in the reaction. Catalysts can lower the activation energy of reaction be stabilizing the transition state. They can also create new reaction pathways with new reaction intermediates that lower the overall activation energy.
045 - Catalyst Classes
In this video Paul Andersen explains how the three types of catalyst classes act to speed up reactions. Acid-base catalysts either add or remove a proton from one of the reactants. Surface catalysts provide active sites where reactants can adsorb and create more successful collision. Enzymes use induced fit to lower the activation energy of the reaction.
046 - Temperature
In this video Paul Andersen explains how the temperature is a measure of the average kinetic energy of particles in an object. The temperature is proportional to the average kinetic energy according to the Kelvin scale. At absolute zero there is no molecular motion and it is at 0K. The Maxwell-Boltzman distribution can be used to measure the average kinetic energy of the particles in a specific example.
047- Heat Exchange
In this video Paul Andersen explains how energy can be transferred from warmer objects to colder objects through heat. Temperature is a measure of the average kinetic energy of the particles in a substance. When two objects are in contact collisions between the particles will transfer energy from the warmer object in the form of heat.
048 - Energy Transfer
In this video Paul Andersen explains how energy can be transferred from one system to another. In a closed system the energy can be transferred as either work or heat. Thermal energy transfer is know as energy transfer through heat. During energy transfer the energy of the entire system is conserved.
049 - Conservation of Energy
In this video Paul Andersen explains how energy can neither be created nor destroyed but may be transferred. Energy comes in many forms (including chemical, mechanical, light, electrical, and thermal). In AP Chemistry students must be accountable for interactions involving an increase in volume over time.
050 - Energy Changing Processes
In this video Paul Andersen explains how energy can enter and leave a system. The amount of energy a substance can receive through heating or lose through cooling is measured using the specific heat capacity. Phase changing energy from solid to liquid is known as the enthalpy of fusion and phase-changing energy from a liquid to a gas is known as the enthalpy of vaporization. The energy leaving or entering a chemical reaction is the enthalpy of reaction.
051 - Calorimetry
In this video Paul Andersen describes the history of calorimetry and explains how it can be used to measure energy changes in a system. The specific heat of water is well established and so as a system releases or absorbs energy from a surrounding water bath it can be measured. Calorimeters can be used to measure the specific heat capacity of a substance as well as the enthalpy of fusion, vaporization, and reaction.
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Deutsch: Eine Kerze. Gezeichnet Auf Papier Mit Einem Filzstift, Gescannt, Danach Aufbereitet Mit GIMP., 2003. originally uploaded by de:Benutzer:Drzoom.
"File:Bombenkalorimeter Mit Bombe.jpg." Wikipedia, the Free Encyclopedia. Accessed December 2, 2013.
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Li-on. English: Calorimeter, October 7, 2010. Own work.
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052 - Bond Length and Bond Energy
In this video Paul Andersen explains how the bond length and bond energy are calculated using an energy distance graph. The strength of the bond is determined by the charges in the constituent atoms. As the charge increases the bond energy increases and the bond length decreases. Increasing numbers of bonds will also increase the energy and decrease the length.ex....
053 - Enthalpy of Reaction
In this video Paul Andersen explains how the enthalpy of a reaction can be released in an exothermic or consumed in an endothermic reaction. According to Hess's law if the reaction is reversed the sign of the enthalpy of reaction is also reversed. The overall enthalpy of reaction is the sum of all the individual reactions. A couple of enthalpy of reaction problems are worked out as well.
054 - Intermolecular Potential Energy
In this video Paul Andersen explains the importance of intermolecular forces in chemistry. Intermolecular forces exist between dipoles (like hydrogen bonds), between dipoles and induced dipoles (like Ar and HCl) and between induced dipoles. The energy of the force is based on the size of the molecule and the number of electrons.
055 - Chemical and Physical Processes
In this video Paul Andersen explains the difference between chemical and physical processes. Chemical processes occur when bonds are broken and reformed. Physical processes occur when intermolecular forces are broken and reformed. A gray area exists between these processes which can be either chemical or physical. When an ionic compound is dissolved in water the intermolecular forces separate ions. This process could be either physical or chemical.
056 - Biological and Polymer Systems
In this video Paul Andersen explains how the structure of a biomolecule fits the function of the biomolecule. For example and enzyme must interact correctly with a substrate to lower the activation energy, The covalent and non-covalent interactions are both important in shaping large molecules. Knowledge of structure allows humans to create useful synthetic polymers (like nylon or kevlar).
057 - Entropy
In this video Paul Andersen explains that entropy is simply the dispersion of matter or energy. He begins with a series of video that show the natural direction of processes. According to the second law of thermodynamics the entropy may never decrease in a closed system. In irreversible processes the entropy will increase over time. The entropy will increase as volume increases, phases change, temperature increases and as the moles of products increases.
058 - Spontaneous Processes
In this video Paul Andersen discriminates between spontaneous (or thermodynamically favored) processes and those that are not spontaneous. A spontaneous process requires no external energy source. If the enthalpy change in a reaction is negative and the entropy is positive a spontaneous process will occur.
059 - Using Gibbs Free Energy
In this video Paul Andersen explains how you can use the Gibbs Free Energy equation to determine if a process is spontaneous or not spontaneous. If the ?G is less than zero the process is spontaneous. If the ?G is greater than zero the process is not spontaneous. If the ?G is equal to zero the process is at equilibrium. The ?H, ?S, and T are all used to calculate ?G.
060 - Driving Nonspontaneous Processes
In this video Paul Andersen explains how you can drive non spontaneous processes by adding external energy (like electricity or light) or by coupling it to a spontaneous process (like the conversion of ATP to ADP)
061 - Kinetic Reaction Control
In this video Paul Andersen explains how a spontaneous process may take either the thermodynamically controlled or the kinetic controlled pathway. If the activation energy determines the path taken then the process is under kinetic control. This accounts for the variation if products from a similar reaction at different temperatures.
062 - Reversible Reactions
In this video Paul Andersen describes how reversible reactions achieve equilibrium as reactants are converted to products and products are converted to reactants. A model shows how forward reaction rates and reverse reactions rates approach equality at equilibrium. Physical, chemical, biological, and ecological examples of reversible reactions are included.
063 - The Reaction Quotient
In this video Paul Andersen explains how the reaction quotient is used to determine the progress of a reversible reaction. The reaction quotient (Q) is the ratio of the concentration of products to the concentration of reactants. The reaction quotient will equal the equilibrium constant when the reaction is at equilibrium. Model and graphical analysis of Q is included.
064 - Equilibrium
In this video Paul Andersen explains how equilibrium is achieved in a reversible reaction. When the rate of the forward reaction is equal to the rate of the reverse reaction the system is at equilibrium. Graphical analysis of equilibrium is included along with a walkthrough of several calculations.
065 - The Equilibrium Constant
In this video Paul Andersen defines the equilibrium constant (K) and explains how it can be calculated in various reversible reactions. The equilibrium constant is a ratio of the concentration of the products to the concentration of the reactants. If the K value is less than one the reaction will move to the left and if the K value is greater than one the reaction will move to the right.
066 - Le Chatelier's Principle
In this video Paul Andersen explains how Le Chatelier's Principle can be used to predict the effect of disturbances to equilibrium. When a reversible reaction is at equilibrium disturbances (in concentration, temperature, pressure, etc.) will be offset to reach a new equilibrium. For examples when more reactants are added the reaction will move to the right to reestablish the equilibrium constant.
067 - Equilibrium Disturbances
In this video Paul Andersen explains how disturbances to a reversible reaction at equilibrium affect the equilibrium constant and the reaction quotient. For example if the concentration is changed the reaction will move to reestablish the equilibrium constant. If the temperature is changed a new equilibrium constant will be established.
068 - Acid-Base Equilibrium
In this video Paul Andersen explains how acid-base chemistry can be understood in terms of equilibrium. Water is present in all acid-base chemistry and is amphoteric in nature. The Ka and Kb values can be used to determine the strength of an acid or a base. Titrations can be used to student neutralization reactions between strong and weak acids and bases.
069 - pH and Buffers
In this video Paul Andersen explains how buffer solutions maintain pH in a solution. A buffer solution is made up of a weak acid and its conjugate base. As strong acids or bases are added the pH remains stable. A good buffer solution has a pKa value equivalent to the pH and equal amounts of the weak acid and the conjugate base.
070 - Solubility
In this video Paul Andersen explains how the dissolution of a solute in a solution can be explained as a reversible reaction. Bonds in the solid solute are broken and the ions are dissolved in a solution. The Ksp (or solubility product constant) can be used to explain the solubility of various salts.
071 - Free Energy and the Equilibrium Constant
In this video Paul Andersen explains how thermodynamic and equilibrium reasoning can be related through changes in free energy and the equilibrium constant. When the delta G is negative the reaction shifts to the right or favors products. When the delta G is positive the reaction shifts to the left or favors reactants. In biological systems exergonic reactions (like cellular respiration) can be linked to endergonic reactions (like the production of ATP).