Chemistry: Challenges and Solutions
Models of the Atom (animation)
The early 20th century brought a succession of scientific models, or theories, to describe the atom and its components. As experiments revealed more about subatomic particles, atomic models evolved from Thomson’s “plum pudding model,” to Rutherford’s nuclear model, then to Niels Bohr’s planetary model, and eventually to the currently-accepted quantum-mechanical model.
Unit 1 Matter and the Rise of Atomic Theory: The Art of the Meticulous
This introduction to chemistry, from a practical discipline in ancient times to the science it is today, touches on both major advances and discarded theories. The contributions to atomic theory of Dalton, Proust, Lavoisier, as well as those of the Arabic scientist, Jābir ibn Ḥayyān, who died in 803 AD, are discussed. The modern-day application of chemists' quest to refine and purify substances is demonstrated at a solar panel plant where a common material — silica sand — is transformed into photovoltaic panels.
Unit 2 The Behavior of Atoms: Phases of Matter and the Properties of Gases
By documenting how particles behaved in different states of matter, 19th century scientists gained a deeper understanding of the atom. Avogadro's suggestion that a volume of any gas, under equal temperature and pressure, contains the same number of particles, led to an understanding of the relationship between temperature and pressure and to the Ideal Gas Law. Today, a fourth state of matter, the supercritical fluid, may possibly help mitigate the impact of burning fossil fuels by storing carbon dioxide as a supercritical fluid within the Earth. Researchers are developing methods to pack hydrogen gas into carbon nanostructures for use as fuel in hydrogen-powered vehicles.
Unit 3 Atoms and Light: Exploring Atomic and Electronic Structure
In the early 20th century, identification of the internal parts of the atom (electrons, protons, and neutrons) led to a modern subatomic theory. Meanwhile, the study of atomic spectra—the light given off by atoms at definite wavelengths—led to the Bohr model of the atom, where electrons exist at distinct energy levels and move between these levels by absorbing and emitting discrete quanta of energy. The measurement of atomic spectra has applications in astrophysics as well as forensic chemistry.
Unit 4 Organizing Atoms and Electrons: The Periodic Table
Before scientists knew about the subcomponents of atoms, they organized elements based on physical and chemical properties. Dmitri Mendeleev developed an early Periodic Table of the 63 known elements, leaving gaps for the discovery of new elements to come. His table was enhanced by Henry Moseley who enabled today's ordering of the elements, based on the number of protons. Scientists at Lawrence Livermore Labs have synthesized new elements up to atomic number 118. These new elements further our understanding of the mysteries of the atom and also have useful applications in forensic science.
Unit 5 Making Molecules: Lewis Structures and Molecular Geometries
When molecules form, the elements bond to one other by sharing or exchanging electrons. The “Octet Rule” predicts how atoms will combine to fill the eight slots in their outer shells. The program shows how this simple, but powerful, bonding mechanism — when combined with electron pair repulsion — leads to the 3-dimensional structure of molecules. Using these principles, scientists can build molecules that disrupt the chemical processes of cancer cell replication. Lewis structures, atomic model configurations, VSEPR theory and radicals are discussed.
Unit 6 Quantifying Chemical Reactions: Stoichiometry and Moles
To manipulate chemical reactions on a large scale, scientists use stoichiometry to quantify those reactions and make sure that there are just the right amount of reactants and products. Without it, reactions can be incomplete, with expensive materials wasted and harmful byproducts created. Using stoichiometry, scientists are creating chemicals that take the place of petroleum in fabricating sustainable materials. At different lab, scientists are mimicking the process of photosynthesis to convert the Sun’s energy into storable chemical energy.
Unit 7 The Energy in Chemical Reactions: Thermodynamics and Enthalpy
By first looking at work and heat, the course adds another dimension: the energetics of chemical reactions. This study of thermodynamics can lead to predicting how chemical reactions will proceed or how much energy is required or released during the reactions. To better understand chemical reactions, a new thermodynamic value called “enthalpy” is introduced. Practical applications of bond enthalpies, calorimetry, and other measurements of the energy in chemical reactions is helping scientists optimize the use of crop waste for biofuels and build more efficient automobile engines.
Unit 8 When Chemicals Meet Water: The Properties of Solutions
Solutions are uniform mixtures of molecules in which any of the phases of matter can be dissolved in another phase. Whether solids, liquids, or gases, solution chemistry is important because most chemical reactions, whether in the laboratory or in nature, take place in solutions. In particular, solutions with water as the solvent – aqueous solutions – are the core of all biology. Extending the particle model of matter to solutions enables chemists to predict what will happen to a deep-sea diver who breathes different mixtures of gases, or to the life forms in the ocean as CO2 levels rise in the atmosphere.
Unit 9 Equilibrium and Advanced Thermodynamics: Balance in Chemical Reactions
Some chemical reactions, like metal rusting, happen spontaneously. Others require external energy in order to occur. Expanding upon the basic thermodynamics of enthalpy from Unit 7, disorder (entropy) and Gibbs free energy are key to understanding what makes chemical reactions proceed thermodynamically. When the thermodynamics of a reaction prevent it from reaching completion, (both products and reactants are always present) it is called equilibrium. When equilibrium reactions are disrupted, such as the binding of oxygen by hemoglobin, as in carbon monoxide poisoning, it can be life threatening. Conversely, controlling an equilibrium reaction is important in chemical manufacturing, like in the synthesis of ammonia.
Unit 10 Acids and Bases: The Voyage of the Proton
Acids and bases are important to many chemical processes: maintaining a stable internal environment in the human body, baking a delicious cake, or determining whether a lake can support aquatic life. Reactions involving acids and bases can be described through the transfer of protons – single H+ ions. For chemists, the number of those acidic hydrogen ions can be quantified by using the pH scale. The reactions of acids and bases, which can be monitored with indicators, can range from corrosive behavior to neutralizations that leave no acids or bases behind. To understand the controlling of pH of solutions, buffers are discussed in the laboratory and in the chemistry of the bloodstream.
Unit 11 The Metallic World: Electrochemistry and Coordination Compounds
Electrochemistry is the study of chemical reactions in which the reactants transfer electrons from one compound to another. In any electrochemical process, one species will lose electrons and get oxidized, while the other must concurrently gain electrons and get reduced. So, these processes are called “redox” reactions. If the flow of electrons during a redox reaction can be controlled, energy can be stored inside batteries for later use or the surfaces of metals can be electroplated. Nearly all of these processes involve metals transferring their electrons, and in human biology, metals do most of the redox chemistry. The role of the redox chemistry of cobalt is in preventing birth defects and controlling heart disease.
Unit 12 Kinetics and Nuclear Chemistry – Rates of Reaction
The speeds of chemical reactions vary tremendously. TNT (Trinitrotoluene) detonates in a fraction of a second, whereas the iron in a car muffler takes years to rust through. A trip to an amusement park offers many analogies to help understand the factors that control reaction rates. For example, the rate of synthesis of cancer medicines can be increased by carefully-chosen catalysts. The connection between reaction rates and nuclear chemistry is underscored by examining how radioactive decay is used in PET scans.
Unit 13 Modern Materials and the Solid State: Crystals, Polymers, and Alloys
n this unit, the focus shifts from fluids and their solutions to solids, whose atoms and molecules are fixed in definite arrangements. Examples of molecular configurations range from crystals in a mineral collection, to metal alloys, to long polymer chains. One promising area of polymer research may allow the delivery of essential drugs such as insulin to be taken orally and delivered directly into the bloodstream. Bioplastic-enclosed nanoparticles encasing the drug have the ability to withstand the body’s corrosive digestive system. Extremely high-temperature resistant alloys are another important application of the chemistry of the solid state.