Wednesday, December 28, 2022

Chemistry: Challenges and Solutions

A video-based instructional series in chemistry with accompanying website for high school and college classes. 13 half-hour programs, online text, course guide, interactive lessons, historical timeline and periodic table.

Chemistry: Challenges and Solutions teaches general chemistry concepts using real-life challenges in energy, materials development, biochemistry, and the environment.

The course zeroes in on essential topics that are generally taught in introductory chemistry, providing a strong foundation for learners to pursue further study in science or a liberal-arts education. Videos include dramatic demonstrations of key principles, interviews with scientists who are doing current research related to these fields, animations, and clear explanations. Each video is hosted by a different working chemist – together, they show a diversity of chemistry professionals and the challenges chemistry is addressing for society. The on-line text covers key concepts with clear text and illustrations, while interactive labs provide simulations of chemical processes online.

Series produced in 2014 by the Harvard Smithsonian Center for Astrophysics. As of the time of publication, episodes stream at the Annenberg Learner website.

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. This program traces the story of how humans have always practiced chemistry; how, over time, it developed from a practical discipline into a science. Today, we keep up the chemists’ tradition to refine and purify substances. A current, real-life application of the “art of the meticulous” is the refining and purification of pure silicon from a common material—silica sand—for advanced electronics, such as cell phones and solar cells. Segments: The Origins Of Chemistry, Separating The Beach, Sand To Sun, The History Of Oxygen, Making Water The Hard Way, Atomic Manipulation. Hosted by Christopher Morse.

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. This program explores the phases of matter—solids, liquids, and gases—and how particles in a given phase interact with each other. Phase diagrams explain at what temperature and pressure a given substance will be in a solid, liquid, or gas phase. Practical problems, like how to safely store enough hydrogen gas to power an automobile, are solved by understanding the different behaviors of solids, liquids, and gases. Understanding the relationships between temperature, pressure, and volume eventually led to the Ideal Gas Law, which provides the platform for examining the conditions under which matter can form a supercritical fluid. Researchers are investigating underground sequestration of supercritical carbon dioxide to mitigate the environmental impact of burning fossil fuels. Segments: The Behavior of Atoms, Phase Diagram, A Model of a Gas, Hydrogen Storage, Gas Laws, Volume = Temperature, Supercritical Fluid. Hosted by Mala Radhakrishnan.

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. Segments: Atoms and Light, Making Light with Electrons, Atomic Models, Cathode Ray Tubes, Rutherford’s Experiment, The Flame Test, Observing Sunlight, Emission Spectra, Forensic Spectroscopy. Hosted by Michael McCarthy.

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. For centuries, chemists tried different methods to organize elements around patterns of chemical and physical trends, or regularities, eventually leading to the modern periodic table. Electron configuration is a powerful predictive tool, a simple extension from the periodic table. Physical characteristics, including atomic radius and reactivity, all depend on electron configuration and can be teased from a careful understanding of the periodic table. A living document, the periodic table is continually updated as new manmade heavy elements are discovered in research laboratories. Segments: Arranging the Elements, Periodic Trends in Reactivity, Electron Configuration, Reactivities of Alkaline Earth Metals, Seaborg’s Elements, Synthesizing New Elements. Hosted by Mala Radhakrishnan.

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. Molecules can form when atoms bond together by sharing electrons and can be represented by a useful shorthand called Lewis Structures. These visual representations provide information to predict the three-dimensional shapes of molecules using valence shell electron pair repulsion (“VSEPR”) theory. Understanding how atoms bond within molecules provides insight into cell replication. Building on this knowledge, the shapes of molecules reveal the effectiveness of important antibiotics such as penicillin, and scientists can manipulate shapes of molecules to help design new cancer-treating drugs. Segments: Lewis Structures and Radicals, Free Radicals in Cell Replication, The Geometry of Molecules, Penicillin and VSEPR, Designing New Cancer Drugs. Hosted by Elizabeth Vogel Taylor.

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. Stoichiometry gives us the quantitative tools to figure out the relative amounts of reactants and products in chemical reactions. Balancing the number of atoms on each side of the equation, calculating the amount of each reactant, and figuring out which reactant will run out first are all fundamental principles when designing any chemical reaction. These principles are applied when splitting water into hydrogen and oxygen for energy, manufacturing sodium iodide for radiation detectors, and producing common chemicals from renewable resources. Segments: Quantifying Chemical Reactions, A Balanced Equation for Fuel, Making Water 2:1, Calculating Molar Mass, Limiting Reagent, Finding the Limiting Reagent, Sustainable Chemistry, Hosted by David Song.

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. The phrase “chemical reaction” conjures up images of explosions, bubbling gases, flames, and smoke. So many chemical reactions have visible results because energy is being transferred from one form to another—the realm of thermodynamics. Thermodynamics provides rules for predicting the progress of a reaction and for harnessing the energy released. It is key to solving pressing engineering problems, such as making the next generation of cleaner, and more efficient, automobile engines. Segments: Energy In Chemical Reactions, Exothermic Reactions, Flame Tornado, Endothermic Reactions, Heat Absorber, Measuring Heat, Mississippi Biofuels, Bond Enthalpy, Fighting the 2nd Law. Hosted by Nicole Labbe.

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. The majority of chemical reactions happen in solutions—whether inside an espresso machine or in a human cell. For example, when we breathe, the nitrogen in the air dissolves in our blood. Henry’s Law gives us the power to predict, prevent, and treat “the bends”—a life-threatening condition that can happen to SCUBA divers when nitrogen in the blood comes out of solution and forms gas bubbles. Solution chemistry provides tools to measure the concentration of components of solutions, like the CO2 levels in ocean water. Knowing the concentrations of components in solutions can help determine the health of the world. Segments: When Chemicals Meet Water, What is a Solution?, The Coffee Solution, The Greatest Solvent, Solids in Solution, Gases in Solution, The Ammonia Fountain, CO2 in the Water. Hosted by Adam Brunet.

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. Light a match and chemical change happens in a one-way process: Reactants are transformed into products. But there are many chemical reactions called “equilibrium reactions” that operate in both directions: with reactants and products always present. The Unit 9 video will show how chemical equilibrium works, the essential role it plays in the function of the human body, and how it is exploited in chemical processes such as ammonia synthesis, a process that provides food for up to half the world’s population. Segments: Equilibrium and Advanced Thermodynamics, Dynamic Equilibrium, The Equilibrium Constant, Le Chatelier’s Principle, Counteracting Poison, Pressure and Le Chatelier’s Principle, Temperature and Le Chatelier’s Principle, The Haber Process. Hosted by Wilton L. Virgo.

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. Acids and bases are found all around us, and the currency of acid-base chemistry is the proton, or hydrogen ion. Acid-base chemistry is part of everyday life, from baking and the food we eat to the innumerable reactions that keep the human body alive. Acid-base chemistry is measured on the pH scale—the concentration of hydrogen ions in a solution. Buffers can control pH, whether used in the lab or in the acid-base components of human blood. The role of acids and bases will be shown in food—from the rise of a cake to the making of cheese. In the environment, acid rain plagues industrial portions of the world; the chemical nature of acid rain reactions and the environmental response and impact are part of acid-base chemistry. Segments: Acids and Bases, Corrosive Acids and Bases, A Cheesy Weak Solution, Baked Reactions, Acidic Pond, Buffered Lemonade, Removing Acids from the Body. Hosted by Adam Brunet.

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. Metals allow the transfer of electrons through a process called oxidation-reduction, or “redox,” when one species gains electrons while another loses them. Chemists take advantage of this process by using electron transfers to power the batteries in our flashlights, phones, or cars. In biochemistry, trace metals, such as cobalt in Vitamin B12, often drive chemical reactions that are essential for human health. Redox reactions also occur without metals, as is the case when lightening hair color. Segments: The Metallic World, Powered by Redox, Oxidation-Reduction Reaction, Redox: Creating an Electric Current, Vitamin B12, Folic Acid in Fetal Development, Non-Spontaneous Redox Reaction, Hair, Highlights and Redox. Hosted by Catherine L. Drennan.

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. From an instantaneous explosion to the slow rusting of iron, the rates at which different chemical reactions proceed can vary tremendously depending on several factors, including temperature and concentration. Sometimes, like with the rotting of food, chemists want to slow down reaction rates. But often, the goal is to speed them up—and one way to do this is to use a catalyst. In this video, we will learn about catalysts and how using them can lead to cheaper, more effective, and more sustainable drug production processes. We will also discover how the rates of some reactions, like nuclear decay, are unchangeable, and how scientists take advantage of this, using PET scans to reveal the presence of disease. Segments: Activation Energy, Catalysts, Elephant’s Toothpaste, Molecular Architects, Radioactivity, PET Scans. Hosted by Wilton L. Virgo.

Crystals, Polymers, and Alloys. In 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. While chemical reactions in gases and liquids are essential to the understanding of chemistry, the chemistry of solid-state materials characterizes most of the interactions we have with matter on a daily basis. Chemists take advantage of the complexity of solids to engineer new materials, including nanoparticles, polymers, and advanced metal alloys. These new materials have many potential applications in sensors, advanced drug delivery systems, and space exploration. Today, modern materials are following a heritage—one that can be traced back to earlier civilizations—in which the properties of solids are manipulated to advance human needs. Segments: Modern Materials And The Solid State, Atomic Arrangements, Carbon Nanotube Sensors, Early Plastics, Making Nylon, Pharmaceutical Polymer Research, High Temperature Alloys. Hosted by Ainissa Ramirez.

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